1998 FRUIT & VEGETABLE RESEARCH REPORT NOVEMBER 1998 RESEARCH REPORT SERIES NO. 15 ALABAMA AGRICULTURAL EXPERIMENT STATION DR. RONALD L. SHUMACK, INTERIM DIRECTOR AUBURN UNIVERSITY, ALABAMA CONTENTS FRUIT PAPERS Yield of Satsumas the Year After a Freeze ................................................... 1 Fig Cultivar Evaluation Creates Interest and Fine Dining ........................................ 1 Comparison of Guardian Rootstocks Selections to Other Peach Rootstocks for Use on Peach Short Life Sites-An Update ................... 2.. Evaluation of Fungicide Spray Programs for Peach Scab and Brown Rot Control on Peaches ............. 3 Fertigation Evaluation With Harvester Peach ................................................. 4 Gibberellic Acid and Ethephon Combination, Southeast Answer to Chemical Flower Bud Thinning and Early Spring Freezes ........................... ....................... 4 Evaluation of Abound For Peach Scab and Brown Rot Control on Peaches ........................... 6 Evaluation of Actigard (CGA-245704) for Control of Bacterial Spot of Peach ........................ 6 Genetic Diversity Evaluations of Threatened Ozark and Allegheny Chinkapin Populations ............... 7 Evaluation of Fungicides for Scab Control on Pecans ........................................... 8 Pecan Cultivars for Low-Input Orchards and Home Plantings ..................................... 9 Evaluation of Household Bleach for Pecan Scab Control ........................................ 9 VEGETABLE PAPERS Genome Mapping in Watermelon Populations Segregating for Fusarium Wilt Resistance .............. 10 6-Carbon Volatile Compounds Differentially Alter Xanthomonas campestris Metabolism ................ 11 Gummy Stem Blight Resistance In Watermelon ............................................... 12 Viruses in Commercial Cantaloupe and Watermelon in Alabama ................................ 12 Summer Heat Takes Toll on Bell Pepper Production, but Organic Mulches Improve Production Potential ........................................................ 13 NitrogenSources and Rates for Bell Pepper Production ........................................ 14 Picking Methods Affect Yield, Grade Distribution, and Retail Value of Colored Bell Pepper .............. 15 Altering Size and Yields of Irish Potatoes .................................................. 16 Despite the Weather - the Irish Potatoes LaRouge and NDO 2686-6R Performed Well .................. 17 Irrigation Increased Yield of Irish Potato.................................................... 18 Optimizing In-row Spacing for Sweetpotatoes ................................................ 20 Sweetpotato Yield Response to Irrigation at Two Nitrogen Rates .................................. 20 Evaluation of Botran for Plant Bed Disease Control of Sweetpotatoes .............................. 22 Evaluation of Fungicides for Control of Early Blight on Tomato .................................. 22 Tomato 1PM Program a Success in Alabama in 1998 .......................................... 23 Evaluation of Penncozeb for Control of Septoria Leaf Spot on Tomato .............................. 24 Responses of Field-Grown Tomatoes to Nitrogen Sources ...................................... 25 New Hot Set Tomato Cultivars-Observations from the Field .................................... 26 A Comparison of Dumas-N and Kjeldahl-N for the Diagnosis of N Nutrition in Vegetables .............. 27 Information contained herein is available to all persons regardless of race Color sex, or national origin. AUTHORS Randy Akridge Superintendent Brewton Experiment Field Mahefa Andrianifahanana Graduate Research Assistant Dept. of Plant Pathology Mary Baltikauski County Extension Coordinator Geneva County Jim Bannon Director E.V. Smith Research Center Richard Beauchamp County Extension Agent Elmore County Tom Beckman USDA-ARS, S.E. Fruit and Tree Nut Research Lab. Byron, GA Bobby Boozer Area Horticulturist Chilton Area Horticulture Substation Shay Bomberger Graduate Research Asst. Dept. of Horticulture Jason Burkett Superintendent- Horticulture Unit E.V. Smith Research Center Lee Campbell Research Technician Dept. of Plant Pathology Arnold Caylor Superintendent North Alabama Horticulture Substation Tony Dawkins Superintendent Sand Mountain Substation Bill Dozier Professor and Dept. Chair Dept. of Horticulture Fenny Dane Assistant Professor Dept. of Horticulture Bob Ebel Assistant Professor Dept. of Horticulture Beth Guertal Associate Professor Dept. of Agronomy and Soils Bill Goff Professor and Extension Horticulturist Dept. of Horticulture Derenda Hagemore Research Office Station Associate North Alabama Horticulture Substation Christine Harris Graduate Research Assist. Dept. of Horticulture Leigh K. Hawkins Graduate Research Assistant Dept. of Horticulture David Himelrick Professor and Extension Horticulturist Dept. of Horticulture Joe Kemble Co-Editor Extension Horticulturist and Asst. Professor Young-Seok Kwon Visiting Scientist, National Alpine Agric. Experiment Station, South Korea Ruhui Li Research Associate Dept. of Plant Pathology Ron McDaniel Superintendent Gulf Coast Substation Harry A. Mills Professor, Dept. of Horticulture Univ. of Georgia, Athens John F. Murphy Asst. Professor Dept. of Plant Pathology Richard Murphy County Extension Agent Houston County Monte Nesbitt Area Horticulturist Gulf Coast Substation Andy Nyczepir USDA-ARS S.E. Fruit and Tree Nut Research Lab Byron, GA John Owen Superintendent Piedmont Substation Michael Patterson Professor and Extension Weed Specialist Dept. of Agronomy and Soils Malcomb Pegues Asst. Superintendent Gulf Coast substation Jim Pitts Superintendent Chilton Area Horticulture Substation Daniel Porch County Extension Agent Blount County Marvin Ruf Asst. Superintendent Sand Mountain Substation Edward Sikora Assoc. Professor and Extension Plant Pathologist Dept. of Horticulture Eric Simonne Asst. Professor and Extension Horticulturist Dept. of Horticulture Bryan Wilkins Graduate Research Assistant Dept. of Horticulture Edgar Vinson, III Research Technician Dept. of Horticulture Mark Wilson Former Asst. Professor Dept. of Horticulture Geoff Zehnder Professor and Extension Entomologist Dept. of Entomology 1998 FRUIT AND VEGETABLE RESEARCH REPORT I FRUIT PAPERS YIELD OF SATSUMAS THE YEAR AFTER A FREEZE Monte Nesbitt, Bill Dozier, Ron McDaniel, and Malcomb Pegues A test was initiated at the Gulf Coast Substation in Fairhope to compare placement and flow rates of microsprinklers in 'Owari' satsumas for freeze protection. Budded trees were planted in March 1990. Tree spacing was 15 feet x 25 feet. Seven treatments were applied including: control with no protection, control with typical soil banking around the crown of the tree, low volume (11 gph) microsprinkler placed on ground under tree, high vol- ume microsprinkler (24 gph) placed on ground under tree, high volume microsprinkler placed in canopy, high volume microsprinkler placed in canopy with low volume microsprinkler on ground, and high volume microsprinkler placed in canopy with high volume microsprinkler on ground. No significantly damaging frost or freeze events occurred until 1996. On February 2, 1996, an advective freeze occurred at the Gulf Coast Substation. The lowest recorded tempera- ture at the test site was 15 0 F. Temperatures ranged from 15 0 F to 34 0 F for a period of 85 hours. Irrigation was activated when temperatures dropped to 33 0 F, and ran continuously for 87 hours. A second significant freeze event occurred on March 8, 1996, with nightly low temperatures ranging from 27 to 32 0 F over a four day period. During this freeze, irriga- tion was applied at night, because daytime temperatures were well above freezing. As shown in the 1996 and 1997 Fruit and Vegetable Research Reports, high volume microsprinklers decreased foliage loss in the 1996 freezes, and enabled the trees to produce a small amount of fruit (7 pounds/tree in the best treatment). Non-irrigated checks lost all their leaves, but did not sustain severe injury in the test plot. Unprotected satsumas were killed at other locations in the county in 1996. In mid-January of 1997, freezing temper- atures as low as 23 0 F were recorded at the test site, and the freeze protection system was used again. Some leaf injury occurred on the outer periphery of the tree canopies, but did not appear to be significant. Yields in 1997 averaged from 306 to 361 pounds per tree. The differences in yield between treatments in 1997 were not statistically signifi- cant. The 1996 freezes were not severe enough in the test plot to have an effect on 1997 yields. Temperatures colder than 15 0 F could give different results. AVERAGE YIELD OF OWARI SATSUMAS IN 1997 Treatment Average yield (lb./tree) Control (no protection) 306 - Control (banked) 327 II gph ground 358 24 gph ground 361 24 gph canopy 355 24 gph canopy/I I gph ground 310 24 gph canopy/24 gph ground 360 FIG CULTIVAR EVALUATION CREATES INTEREST AND FINE DINING Bobby Boozer and Jim Pitts In 1997, a fig planting was established at the Chilton Area Horticulture Substation to evaluate different cultivars of fig under Central Alabama growing condi- tions. Cuttings were collected from several sources, most of which the true name is unknown. The interest is not in the name, but in suitable cultivars with traits that would produce quality figs in small scale production and market- ing and introduce home owners to figs varying from the typical "Brown Turkey", "Celeste", and "Magnolia" which are most common in our area. While the 1997season produced a small amount of fruit on several of the cultivars, the 1998 season provided enough fruit to compare fruit. It became apparent that sev- eral of the cultivars were identical and others were not cor- rectly named by the source. The ability to separate and cor- rectly name each of the cultivars would be desirable, but may not ever fully be accomplished with certainty. This does not distract from the objectives stated earlier. Tree and fruit characteristics will be compiled and provided to any- one interested in following the progress of this study. 2 COMPARISON OF GUARDIAN ROOTSTOCKS SELECTIONS TO OTHER PEACH ROOTSTOCKS FOR USE ON PEACH SHORT LIFE SITES -AN UPDATE Bob Ebel, Bryan Wilkins,Tom Beckman,Andy Nyczepir, David Himelrick, and Jim Pitts Peach Tree Short Life (PTSL) is a problem in many peach orchards in Alabama. PTSL is associated with the ring nematode, Criconemella xenoplax. Soil fumiga- tion has been a principle method of reducing the nematode populations before planting, but with the loss of methyl bromide and other fumigants, development of rootstocks that resist or tolerate the nematode is essential. Guardian rootstock has displayed significantly better survival than 'Lovell' rootstock on sites prone to PTSL. Survival of Guardian on sites prone to PTSL has been well-document- ed. At this time Guardian is a bulk mix of seed collected from the surviving seedlings of the original tree (which was unfortunately lost). Research has continued with selections out of these surviving seedlings. The current study is being conducted to determine horticultural perfor- mance of Guardian selections on a site that has not dis- played symptoms of PTSL. Trees were planted in 1994. Flower buds were killed by frost in 1996. We reported results from 1997 last year. In this year's report, we summarize tree and fruit per- formance for 1998. The date of full bloom varied slightly with the Guardian selections blooming a little earlier than the other rootstocks. Rate of photosynthesis did not vary across rootstocks except for BY520-9 selection 'SL1089' which was slightly lower. Fruit color at harvest varied slightly across rootstocks. Where different, the BY520-9 selections had slightly higher red blush than 'Lovell'. Yield was similar for the BY520-9 and BY520-8 selec- tions as in 1997. 'SL1923' (BY520-8 selection) yielded the most of all rootstocks in 1997 and 1998 with no loss in fruit size. 'SL2170' (BY520-9 selection) yielded the least compared to all other rootstocks in both years. 'Nemaguard', 'Flordaguard' and BY520-8 selection 'SL4028' had variable results for 1998 compared to 1997, COMPARISON OF GUARDIAN ROOTSTOCK SELECTIONS TO OTHER PEACH ROOTSTOCKS Full Fruit Fruit Tree bloom Photosynthesis color weight Yield survival 3/13/1998 1998 1998 1998 1998 1998 % pmoles C0 2 Im 2 /sec. % lb. lb/tree % Standard rootstocks Lovell 39ab 15.6a 52bc 0.373ab 10lab I00a Nemaguard 46ab 15.4ab 66ab 0.347b 10l ab 1 00a Flordaguard 44ab 14.5bc 55abc 0.38l ab 79b 1I00a Guardian rootstock selections BY520-9 selections SL1089 58a 13.9c 53bc 0.386ab 108ab 100a SLI090 41ab 15.9a 63abc 0.345b I 10ab 98a SL2165 37ab 15.9a 69a 0.391ab 103ab I00a SL2170 43ab 15.9a 61abc 0.409a 85b 97a SL3576 53ab 15.5a 62abc 0.358ab 102ab 94a Other rootstock selections 14DR51 46ab 15.4a 55abc 0.351b I 16ab 98a BY520-8 selections SL1923 32ab 15.3ab 54abc 0.385ab 132a 88a SL2243 50ab 16.2a 50c 0.394ab 106ab 97a SL4028 29ab 16.2a 65abc 0.412a 89b 86a the other rootstocks had simi- lar yield both years. Fruit weight was similar both years for all rootstocks. No trees died in 1998, so overall tree survival during the course of this study was the same as last year's. In general, the 'Guard- ian' rootstock selections have performed as well or better than 'Lovell', 'Nemaguard', and 'Flordaguard' in terms of yield, fruit weight, and fruit color in this trial. We plan to continue to track the relative performance of the BY520-9 selections in the hopes of identifying a superior line. ALABAMA AGRICULTURAL ExPERIMENT STATION 1998 FRUIT AND VEGETABLE RESEARCH REPORT 3 EVALUATION OF FUNGICIDE SPRAY PROGRAMS FOR PEACH SCAB AND BROWN ROT CONTROL ON PEACHES Edward Sikora, Bobby Boozer, and Jim Pitts Peach producers have a variety of fung available for use in a spray program. Factors such as tiveness of disease control and cost per application s be considered when developing a fungicide spray gram. Along with these factors, the need to choose gram that addresses disease resistance management s be considered. Growers should be aware that over abuse of a fungicide can lead to development of f strains resistant to that fungicide, as well as all other I cides within the same class. Peach producers in Alabama commonly use as part of their fungicide spray program. Its is rela cheap compared to synthetic fungicides on the mark( can also control a number of fungal diseases (i.e. scab and brown rot). However, it is not consider effective as Captan for scab or brown rot control used in bloom and/or cover sprays. An effective resistant management spray prc relies on reducing the number of applications of a I cide class during the season, using tankmixes of pounds when appropriate, and/or alternating dif classes of fungicides within the spray program durir season. Growers who follow these practices will r the chances for the development of a resistant fungal in their area. In Alabama, peach growers usually appl or three sprays of the fungicide Orbit alone in the pi vest period due mainly to its relatively low cost as w its overall effectiveness in controlling brown rot. Continued use of Orbit in this manner could potentially lead to the development of resistant strains of brown Fungicide rot and loss of Orbit, as well as other B - C - H fungicides (i.e. Indar, Elite, Funginex) in U U U the same class. B C O0 In this study, we compared fungi- B s 0 cide spray programs that consisted of sul- B C C fur or Captan throughout the bloom and cover period. Each of these programs were follow with a preharvest spray pro- B S C gram that evaluated alternatives to the industry standard (two-to-three sprays of B = bloo Orbit) that follow a resistant management U= Unspr strategy. R = Rovr icides The experiment was conducted at the Chilton effec- County Horticultural Substation near Clanton, Alabama, hould on the cultivar Monroe. Treatments were replicated four pro- times with four trees per replication in a randomized com- a pro- plete block design. Fungicides were applied using an air hould blast sprayer at 150 GPA. use or Bravo was applied at bloom for all fungicide pro- fungal grams on 3/30 and 4/7. Cover sprays were applied on 4/15, fungi- 4/27, 5/8, 5/20, 6/3, 6/17, 6/25, 7/8, and 7/15. Preharvest applications were made on 7/22 and 7/28. Fruit were har- sulfur vested on 7/29. A total of 40 fruit were picked from the itively center two trees of each treatment/replication. Percent of et and fruit with scab and percent marketable fruit was deter- peach mined at harvest. Incidence of brown rot and Rhizopus rot red as were determined seven days after harvest following stor- when age at 77 0 F. Weather conditions were warm and wet, favorable ogram for both scab and brown rot development. Programs that fungi- used Captan during the bloom and cover periods had less com- fruit with damage from scab and a significantly higher ferent number of marketable fruit than programs that used sulfur. ng the There were no apparent differences among spray pro- educe grams with regards to brown rot or Rhizopus rot. strain Programs that alternated among classes of fungicides (we y two used Rovral or Captan) in the preharvest period controlled rehar- brown rot as well as the program that used two consecu- rell as tive sprays of Orbit. EFFECT OF DIFFERENT FUNGICIDE SPRAY PROGRAMS ON INCIDENCE OF PEACH SCAB AND BROWN ROT program 1 % Fruit % Marketable % Brown % Rhizopus I1 - H2 with scab fruit rot rot U 100 6.2 2.5 25.0 O 69.3 76.8 3.7 18.1 O 86.2 42.5 15.6 26.2 O 64.3 74.3 6.8 18.7 O 68.1 71.8 5.0 15.0 O 82.5 55.0 I 1.8 33.1 O 92.5 46.8 17.5 26.8 m sprays, C = cover sprays, HI = first preharvest spray, H2 = second preharvest spray, ayed, C = Captan 50WP (5 Ib./acre), O = Orbit (4oz/acre), S = sulfur 80% (9 Ib./acre), al 50WP (2 lb./acre). w 4LL ALBM GIUTR Lb %XI m FNT I111S1TAOT rC 1whJ1 FERTIGATION EVALUATION WITH HARVESTER PEACH Bobby Boozer, Bob Ebel, and Jim Pitts Production of quality peaches requires close atten- tion to many different practices and favorable climatic conditions. March 1998 brought late winter freeze condi- tions which reduced the overall crop load. The month of May brought temperatures more typical of July beginning a season of extremely high temperatures with several extended periods of drought. Under these types of conditions many producers operate irrigation systems if available. This study, while not attempting to determine the merit of irrigation for Southeast peach production, has been set up to determine the potential utilization of irrigation for the purpose of supplying fertilizer. The supplying of fertilizer through an irrigation system is termed "fertigation." For three years fertigation has been carried out using three rates of calci- um nitrate compared to standard surface applied calcium nitrate. The levels of nitrogen supplied represented 0.25 (1/2), 0.37 (3/4), and 0.5 pounds per tree (full rate, 70 pounds nitrogen per acre, 145 trees per acre ) supplied by micro spray type emitters which supply eight gallons of water per hour; a drip emitter treatment which has two one-gallon per hour drip emitters per tree was used to sup- ply a 3/4 rate per tree. Fertigation treatments significantly affected total fruit number (Table 1), but total fruit weight produced was not significantly different. One important consideration given to nitrogen fertilization and to irrigation is the effect on soluble solids (sugar content) and fruit firmness. Both soluble solids and fruit firmness were significantly affect- ed by treatments. The firmest fruit were produced from drip emitter (3/4-N), surface applied (split 2/3-1/3full-N), micro spray (3/4-N), and were significantly higher than micro spray (1/2-N), micro spray (full-N) and surface applied (split 1/3-2/3 full-N). Soluble solids (sugars) con- centration were not as distinctive by treatment with some overlapping but ranged from a low of 10.6 % to a high of 11.5% (Table). TOTAL FRUIT NUMBER,WEIGHT, FIRMNESS,AND SOLUBLE SOLIDS AS AFFECTED BY FERTIGATION TREATMENTS Treatment Fruit no. Fruit wt. Firmness Soluble solids avg./tree kg/tree lb. % Surface 2/3-1/3 140ab 26 8.5a I I.0ab Full - N Micro I/2N 137ab 26 7.4b 10.5c Micro 3/4 N 140ab 25 8.4a I 1.5a Micro Full N I 23b 22 7.4b I 0.5bc Drip 3/4 N 178a 30 8.5a I1.5a Surface 1/3-2/3 N 96b 19 7.4b I 1.0abc ns Numbers with the same letter are not significant at P50.05. This was the third year of this study and the sec- ond year to have fruit to evaluate the effects of fertigation and differing rates of nitrogen. In addition to nitrogen analysis, fruit samples were taken for calcium analysis starting at shuck-off and every two weeks until harvest. The 1997 season contrasted drastically from the 1998 sea- son and so did the results; however, the potential to utilize the irrigation system and to reduce the amount of nitrogen fertilization continues to show promise. GIBBERELLIC ACID AND ETHEPHON COMBINATION, SOUTHEAST ANSWER TO CHEMICAL FLOWER BUD THINNING AND EARLY SPRING FREEZES Bobby Boozer, Bob Ebel, and Jim Pitts Reducing the amount of hand labor needed for fruit thinning and taking advantage of early fruit thinning were the primary reasons behind this study which was ini- tiated in 1996 at the Chilton Area Horticulture Substation. Gibberellic acid has been shown to inhibit fruit bud for- mation in the year following application when applied one to three weeks prior to fruit harvest. Due to the time of application and the cost of application many producers are apprehensive as to the potential use for Southeast peach production. 4 ALABAMA AGRICULTURAL EXPERIMENT STATION ... I II I 1998 FRUIT AND VEGETABLE RESEARCH REPORT 5 For the 1997 season the use of gibberellic acid significantly reduced the amount of time needed to hand thin. While the cost per acre for hand touch up thinning and the cost of gibberellic material was higher than hand thinning only, the net return per acre was higher due to an increase in percent of larger fruit. Due to the concern of late winter freezes, two treatments combined gibberellic acid for flower bud reduction and ethephon for winter bud hardiness and bloom delay. Winter conditions for 1997 were mild and late freezes did not threaten the crop. As a result, the use of ethephon was not needed for freeze protection and both treatments had lower average fruit weight and resulted in lower net return per acre compared to the control. For 1997, the highest net return came from the use of 50 ppm gibberellic acid and 150 gallon per acre spray volume (Table 1). Winter conditions for 1998 contrasted sharply with the winter of 1997. During March 1997, three days of sub-freezing temperatures threatened the crop. Fruit bud losses from February to late March averaged 55 percent for all treatments except for treatments which included the use of a fall ethephon application. Significantly higher thinning times were required by the three treatments receiving fall ethephon, but a larger number of fruit were also saved from freezing conditions. Net returns above labor costs for each treatment and chemical costs, if applicable for a treatment, were highest for 25 ppm gib- berellic acid, 150 gallon spray volume, and ethephon (Table 2.). Comparison of results for 1997 and 1998 for the same treatments are proportional. Where no ethephon was used the 1988 yields (total fruit number) were 87, 85, and 90% lower for the control, 50/150, and 50/300 respective- ly. Where ethephon was used, 50/150/E, there was no dif- ference in yield from 1997 and 1998. The two year aver- age net return was higher than that of the control for 50/150 and 50/150/E by $1794 and $2341, respectively. Results from both years are encouraging for the combination use of gibberellic acid and ethephon as a potential for increasing freeze protection, reducing labor and increasing net returns. This study will continue using the 1998 treatments. Several years with both mild and harsh winter conditions typical of the Southeast are need- ed to build up confidence in any particular treatment. It should also be noted that neither of the chemicals used in this study are currently labeled for peach production in the Southeast. TABLE I.TOTAL FRUIT NUMBER,TOTAL WEIGHT, AND NET RETURNS IN 1997. Treatment Total fruit Total weight Net returns avg.Itree kg/tree $/acre 0 GA3 777 94 50ppm GA3, 538 74 2610 150 gal H 2 0/a 50ppm GA3, 380 57 1378 300 gal H 2 0/a 50ppm GA3, 266 41 -691 150 gal H 2 0/a, Ethephon TABLE 2.TOTAL FRUIT NUMBER,TOTAL FRUIT WEIGHT, AND NET RETURNS IN 1998. Treatment Total fruit Total weight Net returns I avg.Itree kg/tree $1acre 0 ppmGA3 101 19 - 0 ppmGA3, 272 36 2501 Ethephon 25 ppm GA3, 147 28 IIII 150 gal H 2 0/a 25 ppm GA3, 317 46 3845 150 gal H 2 0/a, Ethephon 25 ppm GA3, 64 13 -1590 300 gal H 2 0/a 50 ppm GA3, 81 16 -788 150 gal H 2 0/a 50 ppm GA3, 265 41 3062 150 gal H 2 0/a, Ethephon 50 ppm GA3, 37 8 -2402 300 gal H 2 0/a Return above control deducting expenditures for hand thinning labor and chemicals used in treatments. EVALUATION OF ABOUND FOR PEACH SCAB AND BROWN ROT CONTROL ON PEACHES Edward Sikora, Bobby Boozer, Mahefa Andrianifahanana, and Jim Pitts This experiment was conducted at the Chilton County Horticultural Substation near Clanton, Alabama, on the cultivar Alred Elberta. Treatments were replicated five times with three trees per replication in a randomized complete block design. Fungicides were applied using an air blast sprayer at 150 GPA. Bloom spray treatments were applied on 3/16 and 4/3. A shuck-split spray was applied on 4/16. Cover sprays were applied on 4/27, 5/8, 5/20, 6/3, 6/17, 6/24, and 7/8. Preharvest sprays were applied on 7/15 and 7/20. Fruit were harvested on 7/21. Samples of 60 fruit picked randomly from the center tree of each three tree treatment/replication were rated for scab incidence and severity (recorded as marketability) at harvest. Fruit were stored at 77 0 F for seven days after which time the fruit were examined for incidence of brown rot and Rhizopus rot. The weather conditions in 1998 were warm and wet which favored disease development. Brown rot blos- som blight incidence in the orchard was extremely low so disease ratings for this disorder were not taken. Peach scab pressure was high considering only 36% of fruit from the control blocks were marketable at harvest due to the high incidence of peach scab. Incidence of brown rot fruit rot seven days after harvest was high as noted on the unsprayed control (63% disease). There were no signifi- cant differences among the three Abound treatments and Captan. All fungicide treatments performed significantly better then the unsprayed control for incidence of scab and brown rot and production of marketable fruit. EFFECT OF BLOOM, COVER AND PREHARVEST APPLICATIONS OF ABOUND ON PEACH SCAB AND BROWN ROT Treatments/acre 1 Fruit Marketable Brown Rhizopus with scab fruit rot rot Abound 2SC 27.0a 91.3a 30.3a 12.6a 0.05 lb. a.i. Abound 2SC 22.3a 96.3a 30.0a 8.0a 0.10 Ib. a.i. Abound 2SC 15.6a 96.3a 27.0a 9.0a 0.15 lb. a.i. Captan 4 lb./acre 23.6a 94.0a 46.0ab 12.0a Unsprayed control 96.3b 36.3b 62.6b I 3.3a tAll Abound sprays were mixed with Latron 1956.Treatments followed by the same letter are not significantly different. Marketable fruit based on severity of scab damage at harvest. EVALUATION OF ACTIGARD (CGA-245704) FOR CONTROL OF BACTERIAL SPOT OF PEACH Lee Campbell, Jim Pitts, and Mark Wilson Field tests were conducted to evaluate the effica- cy of Actigard [CGA-245704 (Novartis Crop Protection)] in controlling bacterial spot of peach. Bacterial spot of peach is caused by Xanthomonas campestris pv. pruni and is becoming a major concern for growers in Alabama for two reasons. First, new peach cultivars from California, which have little or no resistance to bacterial spot, are increasingly being grown in Alabama. Secondly, there is no adequate means of controlling this disease. Currently, the only available means, of control is through the use of oxytetracycline (Mycoshield) but grow- ers are concerned that its effectiveness is not consistent. Actigard, which activates the natural defense mechanisms within a plant, has been successful in controlling bacterial diseases of many vegetable crops including those of toma- to and lettuce. Actigard was tested alone and in combina- tion with Mycoshield. These treatment were compared to an untreated control and a Mycoshield treatment. These 6 ALABAMA AGRICULTURAL EXPERIMENT STATION 1998 FRUIT AND VEGETABLE RESEARCH REPORT 7 tests were conducted on three peach cultivars each with varying degrees of resistance to bacterial spot (O'Henry- highly susceptible and Cresthaven and Fireprince-moder- ately susceptible). Actigard was applied weekly (4 oz. a.i./acre) beginning at first leaf bud break and re-applied until one week prior to fruit harvest. Due to extremely dry weather during the spring and early summer, very little bacterial spot development was observed on the cultivars Fireprince and Cresthaven, /but there was substantial infection on the cultivar O'Henry. Fruit was harvested and rated based on the per- centage of fruit surface covered by bacterial spot lesions. Fruit ratings demonstrated that Actigard alone and in com- bination with Mycoshield reduced the number of infected fruit (disease incidence) when compared with the unsprayed control (Table 1). Mycoshield reduced the inci- dence of disease compared to no treatment, but consistent with grower results, this was not a significant decrease in disease. These results also showed that Actigard, Mycoshield, and Actigard + Mycoshield increased the number of marketable fruit by approximately 10%, 16%, and 20%, respectively (Table 2). Actigard provides some control of bacterial spot on highly susceptible cultivars and will increase the amount of marketable fruit. Because copper bactericides are phytotoxic to peaches and Mycoshield is unreliable, Actigard may offer an alternative to these products that will allow growers in Alabama to plant new and improved California peach cultivars. TABLE I. INCIDENCE OF BACTERIAL SPOT ON FRUIT Treatment Total fruit harvested % Fruit infected Control 500 63.8 Actigard 2 486 43.2 Mycoshield 500 51.6 Actigard 2 +Mycoshield 3 500 37.8 ITotal represents the total amount of fruit harvested from 5 blocks from the 3 inside trees of each 5 tree block. 2 Applied at a rate of 4 oz a.i./acre 3 Tank mix TABLE 2. SEVERITY OF BACTERIAL SPOT ON FRUIT Treatment Proportion of fruit rated I as either marketable or unmarketable % Marketable fruit % Unmarketable fruit Control 67.2 32.8 Actigard 2 77.8 22.2 Mycoshield 83.8 16.2 Actigard 2 + Mycoshield 3 87.6 12.4 I Ratings: 0 = clean, no lesions; I = trace 5 or fewer lesions; 2 = 5 to lesions, no cracking; 3 = 25% of fruit covered by lesions, cracking observed; 4 = > 25% of fruit covered by lesions, severe cracking. 2 Applied at a rate of 4 oz a.i./acre 3 Tank mix GENETIC DIVERSITY EVALUATIONS OF THREATENED OZARK AND ALLEGHENY CHINKAPIN POPULATIONS Fenny Dane Conservation organizations must frequently choose which populations of a threatened or endangered plant species to protect. Two goals of any conservation program should be to ensure the long-term survival of the plant species and the maintenance of ecological and evo- lutionary processes. The short-term survival of a species can be accomplished by conserving a sample of a popula- tion in gardens or by storing seeds. The maintenance of evolutionary processes and long-term survival is depen- dent on the genetic diversity of the populations. Genetically diverse populations should be better able to withstand and adapt to environmental change. Molecular markers make it possible to identify populations with high levels of genetic variation. Research has been conducted at Auburn University for the last sev- eral years studying the genetic variation of the American chestnut and the closely related Ozark and Allegheny chinkapin. Both species are threatened by their suscepti- bility to the Asian fungus, Cryphonectria parasitica. This fungus causes the disease chestnut blight, which over a short period of time has resulted in the demise of the American chestnut and severely affected Ozark chinkapin populations in the Ozarks and Allegheny chinkapins in several southern and eastern states. Samples from representative populations of the Ozark chinkapin in Arkansas and Allegheny chinkapins from Louisiana to Florida to Ohio will be evaluated using different types of molecular markers. This research is 8 ALABAMA AGRICULTURAL EXPERIMENT STATION sponsored by the Arkansas National Heritage Commission and the USDA Plant Germplasm Program. Some of the questions that will be addressed are: 1) How does variation in geographically isolated populations compare with the genetic variation of the species as a whole and to species with similar traits. 2) How does the existing genetic variation relate to biogeographic patterns across the range of the species? 3) What are the conservation implications of the distribution of genetic variation within and among popula- tions of this species. Thus far, the results have indicated that relatively high levels of genetic diversity are being maintained with- in the different Ozark chinkapin populations, as compared to species with similar geographic ranges and life history characteristics. Studies of Allegheny chinkapin popula- tions have just been initiated. Research on these popula- tions should lead to a better understanding of the species as a whole and its evolutionary relationship to other species and should be beneficial to conservation programs aimed to conserve this species. EVALUATION OF FUNGICIDES FOR SCAB CONTROL ON PECANS Edward Sikora and Jason Burkett Pecan scab is the most limiting factor to pecan production in the Southeast. To control the disease, grow- ers must maintain a calendar-based spray program from bud break through nut hardening. In 1998, a newly regis- tered fungicide, Abound (Zeneca), was evaluated for its ability to control pecan scab on both leaves and nuts. The test was conducted at the E. V. Smith Research Center in Shorter, Alabama, on a block of 'Cheyenne' pecan trees. Fungicide treatments were applied according to the spray schedule outlined below. Leaf scab ratings were taken on June 11 and nut scab rat- ings were taken on September 2. Incidence of leaf scab was relatively low (6.9%) in 1998 and few differences were observed among fungi- cide treatments. All fungicide treatments had significant- ly less leaf scab then the unsprayed control. Nut scab pres- sure was relatively high (98.5%) and differences were observed among the fungicide treatments. All fungicide treatments had significantly less nut scab then the unsprayed control. Abound applied full season had the least amount of nut scab (5.5%). The Enable, Abound; Super Tin program also performed well in controlling nut scab (15.5%). Nut scab ratings ranged from 20 to 40% for the remaining fungicide treatments. Fungicide (r Unsprayed Abound (9. EVALUATION OF FUNGICIDE SPRAY PROGRAMS FOR PECAN SCAB CONTROL, 1998. ate) % Leaf scab 2 % Nu control 6.9b 98 6 oz) 0.2a 5. it scab .5d .5a Abound (9.6 oz) then Super Tin 80WP (7.5 oz) 0.2a 27.4bc Enable 2E (8 oz) then Abound (9.6 oz) then Super Tin (7.5 oz) I1.3a 15.0ab Enable (8 oz) then Super Tin (7.5 oz) then Abound (9.6 oz) 3.6ab 40.3c Abound (6.4 oz) then Super Tin 80WP (7.5 oz) 3 0. a 20.2b Super Tin 80WP (7.5 oz) 2.1 a 39.5c ITreatments with one fungicide listed consisted of three applications of the fungicide at 14-day intervals then six applications of the material at 21-day intervals; treatments with two fungicides listed consisted of three applications of the first fungicide listed at 14-day intervals then six applications of the second fungicide listed at 21-day intervals; treat- ments with three fungicides listed consisted of three applications of the first fungicide listed at 14-day intervals then three application of the second fungicide listed at 21-day intervals followed by three applica- tions of the third fungicide listed at 21-day intervals. 2 Treatments followed by the same letter are not significantly different. 3 Consisted of four applications of Abound at 7-10 day intervals then six applications of Super Tin at 21-day intervals. PECAN CULTIVARS FOR LOW-INPUT ORCHARDS AND HOME PLANTINGS Bill Goff and Monte Nesbitt By growing resistant cultivars, pecan growers can save $150-200 per acre, assuming a reduction of 10 pesticide applications at $18/application. Perhaps more importantly, genetic resistance pro- vides insurance against pest-related disas- ters. In 1994, for instance, heavy rain in late June-early July in the Southeast pre- vented growers from applying sprays in a timely manner, and much of that year's crop was lost to the disease scab. A resis- tant cultivar, if the resistance were strong, would have weathered the storm with little scab loss. The purpose of this report is to update our list of cultivars suggested for trial plantings for low-input orchards. The following table describes cul- tivars, which appear most promising, and that combine outstanding pest resistance with good horticultural traits. We can sup- ply limited graftwood for testing. Nurseries are beginning to grow trees of the cultivars listed. DESCRIPTION OF OUTSTANDING CULTIVARS FOR TRIAL PLANTING IN LOW-INPUT ORCHARDS. Jenkins 55 nuts/lb 54% kernel Scab rating: Outstanding, consistent at all locations observed This cultivar has a large nut and appears to be an excellent tree with regard to pest resistance. Nut quality is outstanding. Nuts resemble Desirable, except a little smaller. McMillan 56 nuts/lb 51% kernel Scab rating:Very good, light scab observed at some locations. This cultivar has been highly productive and consistent and scab damage on nuts has been very light Harvest is about three days after Stuart Syrup Mill 53 nuts/Ilb 46% kernel Scab rating: Outstanding, consistent at all locations observed. This cultivar has produced good yields, is extremely vigorous, and retains foliage well. Kernels are bright Carter 45 nuts/lb 49% kernel Scab rating: Good, light to moderate scab observed at some locations. This cultivar has an estimated harvest date of October 1 8, and produces a large nut. Veins have been visible on kernels in some years. Esneul 60 nuts/Ib 52% kernel Scab rating:Very good, light scab observed at some locations. This cultivar has good nut quality and is a little smaller than Stuart. It has had good crops under undesirable circumstance. Tinker 50 nuts/Ib 47% kernel Scab rating: Excellent, Consistent, light scab at some locations. This cultivar has very bright and attractive kernels. The tree has remarkable vigor. Little is known about long-term yield potential. Gafford 56 nuts/Ib 50% kernel Scab rating: Excellent, light scab observed at some locations. This cultivar produced a good quality nut and has excellent resistance, but little is known on long- term yield potential. EVALUATION OF HOUSEHOLD BLEACH FOR PECAN SCAB CONTROL Monte Nesbitt and Edward Sikora Pecan Scab is the primary disease problem facing commercial pecan growers. Chemical cost alone for a cal- endar-based spray schedule is approximately $115/acre per year. Pecan Scab is polycyclic, meaning that the infec- tion process repeats itself multiple times each growing season. Good control of scab usually requires six tol0O fungicide applications per year. Pecan growers seeking low cost alternatives for pecan scab control have reported that household bleach is effective when sprayed on a cal- endar schedule in the growing season. Sodium hypochlo- rite, the active ingredient in bleach, when reacting with organic matter releases chlorine, an effective fungicide. It has no residual activity once the bleach solution dries and the chlorine evaporates. A controlled experiment was conducted at the Gulf Coast Research and Extension Center in Fairhope in 1998. The test cultivar, Desirable, was used which is high- ly susceptible to Pecan Scab. At budbreak, branches on 16-year-old trees having six to eight terminal shoots were flagged for identification throughout the growing season. 1998 FRUIT AND VEGETABLE RESEARCH REPORT 9 l0aL AM AR C IT IAFso oo- .1rAI L-X FlFYP I I N 10 1 1% 11 krI N Treatments were applied to flagged branches with a hand sprayer (atomizer). Treatments included an untreated check, four concentrations of bleach (0.5%, 1%, 5%, 10% v/v), two standard fungicides (Super Tin and Abound), and a tank-mix treatment of Super Tin with 1% bleach. Treatment solutions were prepared from a straight dilution using the field rate of 150 gallons of spray solution per acre. Super Tin was applied at 7.5 oz./acre. Abound was applied at 6.4 oz./acre pre-pollination and 9.6 oz./acre post PERCENTAGE OF LEAF AND NUT SCAB ON Two EVALUATION DAT Treatment Leaf scab I July 27 Nut scab 2 July 27 Nut scab 2 Pct Pct. Pc Abound 1.60 0.18 28. Super Tin 2.48 0.62 46. Bleach 1/2% 5.64 9.01 94. Bleach 1% 4.86 9.12 93. Bleach 5% 4.18 8.86 92. Bleach 10% 4.1 1 5.43 93. Super Tin + Bleach 1% 1.66 0.36 40. Untreated Check 6.56 9.8 94. 1 % of leaf area covered with scab lesions 2 % of nut surface covered with scab lesions pollination. Treatments were applied eight times, using the standard schedule of three sprays every 14 days beginning at budbreak, and cover sprays applied every 21 days. Treatments were replicated 10 times. Disease pressure was low in 1998 from budbreak to mid July, yet bleach treatments of 0.5 and 1.0% provid- ed no control of leaf scab. Bleach treatments of 5-10% controlled leaf scab as good as Super Tin; however, these bleach concentrations caused leaf burn typical of sodium toxicity (Table). Bleach, used alone, did not reduce nut scab severity. Bleach mixed with Super Tin gave numerically better control of leaf Sept. 2626and nut scab than Super Tin alone, but the differ- 7 ences were not significant. Nut scab control with 6 Abound was significantly better than Super Tin 8 2 at end of season. Household bleach is not effec- 7 tive in controlling Pecan Scab, because it does 5 not provide residual protection after application. 7 To be effective, bleach would have to be applied every time conditions were favorable for new spore germination and infection. VEGETABLE PAPERS GENOME MAPPING IN WATERMELON POPULATIONS SEGREGATING FOR FUSARIUM WILT RESISTANCE Leigh K. Hawkins and Fenny Dane Genetic linkage maps consisting of several close- ly-spaced DNA markers allow breeders and geneticists to characterize and manipulate plant genes linked to horti- culturally important traits, such as disease resistance. These markers or tags would aid considerably in incorpo- rating the genes of interest from wild relatives for the breeding of new cultivars. There are two types of markers: (1) morphological markers, which include traits that can be easily seen such as fruit color, seed size, rind color, etc.; and (2) molecular markers based on DNA or protein (isozyme) molecules. In cases where few morphological and isozyme differences (polymorphisms) are seen, DNA- based molecular markers are often used for their ability to detect several polymorphisms. These DNA markers include random amplified polymorphic DNAs (RAPDs), amplified fragment length polymorphisms (AFLPs), and simple sequence repeats (SSRs). Watermelon (Citrullus lanatus) suffers from a number of fungal and bacterial diseases that slow plant development and thus reduce financial returns. Worldwide, one of the most economically devastating of these diseases is Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f.sp. niveum (FON). FON has been divided into three races (races 0, 1, and 2) based on responses to different cultivars. Most commercial cul- tivars are resistant to races 0 and 1, but there are no culti- vars resistant to race 2, which is much more aggressive. LRace 2 has been found in Texas, Oklahoma, and Florida.Race 2 10 ALABAMA AGRICULTURAL [;YPF:RIMP:MT qTATInKi i 1998FRUI ANDVEGEABL RESARCHREPOT.. Generating a map of the watermelon genome would be helpful in map-based pre-selection for resistance genes, which would reduce the number of plants to be grown for screening assays. Because there are few mor- phological and isozyme polymorphisms in the watermel- on, it is desired to maximize the number of markers that can be used for generating a highly-saturated linkage map of the genome, particularly around genes of interest. Thus several types of DNA markers will be employed. For this study, the following breeding populations were used to detect markers linked to Fusarium wilt resis- tance. The resistant plant introduction PI-296341 is resis- tant to all three races of FON. This wild watermelon has small, round fruit with bitter, white flesh. The susceptible parent, the red-fleshed watermelon cultivar 'New Hampshire Midget', is susceptible to all three races. A cross between the two parents was used to generate the F 1 generation (hybrid). The F 1 was selfed to create the F 2 population and individual F 2 plants were selfed to create F 3 lines. Several polymorphic RAPD markers were detect- ed in the F 2 progeny. Those markers that fit the expected segregation (3:1) ratio were used in generating a map of the watermelon genome on which 23 linkage groups were detected. Three groups had 2 markers each and one group had 30 markers. The remaining linkage groups each con- tained one marker. This map will be expanded using AFLP, SSR, isozyme, and morphological characters. 6-CARBON VOLATILE COMPOUNDS DIFFERENTIALLY ALTER XANTHOMONAS CAMPESTRIS METABOLISM Bob Ebel, Shay Bomberger, and Fenny Dane Plant metabolism changes in response to attack by pathogens in order to produce chemicals toxic to the pathogen. Some of these toxic compounds are volatile compounds but the mechanism by which these compounds affect the pathogen are poorly understood. In order to study the effects of some of these compounds on growth and metabolism of a plant pathogen Xanthomonas campestris, we used a genetically altered strain of the bac- terium that emits light, or is bioluminescent. Bioluminescent bacteria can be used to study the effect of volatile compounds on metabolic processes within the bacteria. Knowledge of the mechanism by which volatile compounds affect pathogens allows us to develop novel methods of artificially stimulating plant metabolism to enhance its resistance to pathogens. We used three compounds that are produced by plants in response to pathogenic attack, and which were previously shown to be inhibitory to bacterial growth. Xanthomonas campestris was grown in petri plates on nutrient agar. The inhibitory, volatile compounds were applied to the petri plates. We measured bioluminescence using a CCD camera 48 hours after exposing the bacteria to the volatile compounds. The volatile compounds trans-2-hexen-1-ol and cis-3-hexen-l1-ol slightly reduced bacterial growth where- as trans-2-hexenal had a strong inhibitory effect compared to the controls and as shown by the total area of the colony (Table). However, bacteria treated with trans-2-hexen-1-ol and cis-3-hexen-l-ol showed much higher biolumines- cence per pixel. The reason for the higher biolumines- cence is not known, but the volatile compounds may be directly converted to a substrate that is metabolized by the bacteria. When we replaced the volatile compounds with decanal, a known precursor of the luciferase enzyme responsible for producing light in the bacteria, biolumines- cence did not increase for trans-2-hexen-1-ol and cis-3- hexen-1-ol suggesting that these COLONY AREA AND BIOLUMINESCENCE OF X. CAMPESTRIS AS AFFECTED BY VOLATILE COMPOUNDSha volatile compounds are converted to Volatile compounds Total area of colony Bioluminescence Bioluminescence per volatile compounds are converted to (pixel) per pixel pixel after adding decanal substrates for the enzyme. We are Water control 45000 61 245 conducting studies to determine the Propanediol control 47000 41 244 mechanism by which these volatiles trans-2-hexen- I-ol 30000 390 163 cis-3-hexen-I-ol 35000 439 329 affected growth and bioluminescence. trans-2-hexenal 11000 19 91 ~ 1998 FRUIT AND VEGETABLE RESEARCH REPORT I I 12 ALABAMA AGRICULTURAL EXPERIMENT STATION GUMMY STEM BLIGHT RESISTANCE IN WATERMELON Fenny Dane and Young-Seok Kwon Worldwide, gummy stem blight, caused by the fungus Didymella bryoniae (Db) is one of the most destructive fungal diseases of watermelon. As resistance to other diseases has been incorporated into commercial varieties, losses to gummy stem blight have increased. Satisfactory chemical control may be obtained by regular applications of fungicides, but isolates of the fungus resis- tant to currently used fungicides have been detected in commercial watermelon fields in the eastern U.S. It remains imperative to gain a better understand- ing of the inheritance of disease resistance to this disease in watermelon and to be able to incorporate durable resis- tance into commercial varieties. Diagnostic molecular markers linked to gummy stem blight disease resistance are being identified. These markers should facilitate breeding for disease resistance and provide a step toward the identification and manipulation of disease resistance genes in watermelon. Watermelon seedling populations derived from crosses between a susceptible watermelon cultivar (SS4 from Korea) and resistant plant introductions (PI 189225 and 271778 from Africa) were inoculated by spraying plants until runoff with suspensions of Db. Disease sever- ity was rated four days after inoculation. Results from three different seedling tests indicated that gummy stem blight resistance in PI 189225 was inherited as a quantita- tive trait with additive dominant features, possibly influ- enced by several genes as well as the environment (Table). Resistance in PI 271778 was negligible. This makes it more difficult to transfer gummy stem blight resistance into susceptible plant material. It is our intent to facilitate this process using molecular mark- ers. Diagnostic markers linked to disease resistance can then be used as selection tools. A innovative technique (Amplified fragment length polymorphism) has been used to identify markers linked to disease resistance. So far one marker appears associated with disease resistant seedlings. This kind of finding warrants more detailed investigation. GUMMY STEM BLIGHT DISEASE SCREENS OF WATERMELON. Population Mean disease index I Susceptible parent S 3.6ab 2 RI (PI 189225) 2.4def R2 (P1 277178) 3.Iabc (Sx RI) hybrid F 3.0abcd (S x RI) F 2.9bcd (Sx RI) x RI 3.2abc (S x RI) x S 3.7ab (SxR2) hybrid F 3.I1abc (S x R2) F 2 3.4ab (Sx R2) x R2 3.5ab (S x R2) x S 3.5ab (RI x R2) hybrid F 1 2.Ief (RI x R2) F 2 2.4def (RI x R2) x RI 1.9f (RI x R2) x R2 2.7cde SDisease scale: I(< 10% infection) to 5 (75-100% of area infected) 2 Means with the same letter are not significantly different VIRUSES IN COMMERCIAL CANTALOUPE AND WATERMELON IN ALABAMA John F. Murphy, Ruhui Li, Joseph Kemble, Mahefa Andrianifahanana, Edward Sikora, Mary Baltikauski, Gary Gray, Richard Beauchamp, Daniel Porch, and Richard Murphy Plant viruses are a persistent threat to crop pro- duction. While some viruses occur on a frequent basis from one year to the next, others appear on a more spo- radic basis. Knowledge of which viruses occur in a crop and their relative abundance from year to year provides a foundation for the development of management strategies. We have initiated a series of statewide surveys to identify viral diseases in commercial vegetable crops. This report describes our findings from the first year of a two-year survey of viruses in cantaloupe, pumpkin, and watermelon with an emphasis on watermelon. Through assistance of County Extension person- nel, selected cantaloupe, pumpkin, and watermelon fields were surveyed in Geneva and Houston Counties (June, 12 ALABAMAAGRICULTURAL ExPERIMENT STATION 1998 FRUIT AND VEGETABLE RESEARCH REPORT 13 1998), Autauga, Chilton, and Elmore Counties (July, 1998) and Blount County (August, 1998). Typically, 20 randomly selected plants were sampled within a field with each sample consisting of three leaves taken from a single vine. Leaves from each plant (representing a sin- gle sample) were wrapped in a /moistened paper towel, placed in a plastic bag, and transported on ice to Auburn University for analysis. Each sample was tested, using the serological assay ELISA, for each of four viruses known to occur on a fre- quent basis in cucurbits: cucumber mosaic cucumovirus (CMV), papaya ringspot potyvirus (PRSV), water- melon mosaic potyvirus 2 (WMV 2) and zucchini yellow mosaic potyvirus (ZYMV). Fields in three areas of the state were surveyed, South, Central and North Alabama. A visual assess- VIRUSES DETECTED IN CANTALOUPE AND WATERMELON CROPS IN ALABAMA IN 1998 County/Field Viruses South Alabama Geneva Field I (cantaloupe) PRSV Field 2 (watermelon) PRSV Field 3 (watermelon) ZYMV Field 4 (watermelon) ZYMV Houston Field I (cantaloupe) ZYMV (watermelon) ZYMV Field 2 (watermelon) ZYMV Central Alabama Autauga Field I (watermelon) Chilton Field I (watermelon) Field 2 (watermelon) WMV 2 WMV 2 WMV 2, ZYMV Elmore Field I (watermelon) No virus detected North Alabama Blount Field I (watermelon) Field 2 (watermelon) Field 3 (watermelon) Field 4 (watermelon) Field 5 (watermelon) Field 6 (pumpkin) PRSV,WMV 2 WMV 2 PRSV WMV 2 WMV 2 WMV 2 ent. Generally, two types of symp- toms were observed: a typical viral- induced mosaic pattern on leaves (light and dark green patches throughout a leaf) or a bright yellow mottled symptom (bright yellow and green patches throughout a leaf). Serological analysis of foliar tissues (Table) revealed the occur- rence of each of the potyviruses (PRSV, WMV 2 and ZYMV) where- as CMV was not detected in any of the cantaloupe, pumpkin, or water- melon samples. In South Alabama, PRSV and ZYMV were detected with ZYMV occurring on a more frequent basis. Plants in Central Alabama were infected with WMV 2 and ZYMV with WMV 2 clearly being the predominant virus. In North Alabama, PRSV and WMV 2 were identified with WMV 2 occur- ring more frequently than PRSV. Interestingly, a tomato crop heavily ment for virus-like symptoms revealed that a large per- centage of plants in some fields were infected with a virus, though no distinguishing types of symptoms were appar- infected with CMV was immediately adjacent to the pumpkin crop in Blount Co., and yet, no CMV was detect- ed in any of the pumpkin samples. SUMMER HEAT TAKES TOLL ON BELL PEPPER PRODUCTION, BUT ORGANIC MULCHES IMPROVE PRODUCTION POTENTIAL Bobby Boozer, Eric Simonne, Joe Kemble, and Jim Pitts Black plastic mulch for spring vegetable produc- tion has dominated much of the commercial production in the Southeast. For some vegetables, the extreme heat that is encountered early is intensified by the use of black plas- tic. While returning to bare ground production is not desir- able for obvious reasons, the use of organic mulches shows promise. Continued research in organic mulches for bell pepper production was conducted at the Chilton Area Horticulture Substation. Treatments were bare ground, black plastic, hairy vetch, crimson clover, and rye. Fertilization was accomplished through the irrigation sys- tem at a rate of 150 pounds N per acre except for one rye treatment which received 30 percent higher nitrogen. Weeds were controlled in plot middles by the use of Gramoxone. Additional hand weeding was needed in all of the organic mulch and bare ground plots. Due to extremely high temperatures, plant stand survival was reduced on all treatments. Plant stand counts were made on three different dates, four days after planti- ng, 56 days after planting, and 116 days after planting. There were no significant differences in plant stand by day 1998 FRUIT AND VEGETABLE RESEARCH REPORT 13 -4 ALABMA GRIULTRALEXPRENTw STATION1 four, but treatments significantly affected plant stands by day 56 and 116 (Table). Plant growth was affected by the hot climatic conditions and was too variable to be consid- ered significant. Visually, however, the organic mulches appeared to have taller plants. When measurements were made, the average plant heights were: 15-, 16-, 20-, 21-, 21-, 22-inches for black plastic, bare ground, vetch, clover, rye (additional N), and rye, respectively. Fruit pro- duction was reduced and fruit size was small for all treat- ments. A strip harvest was made on 14 July and a graded harvest was made on 4 September. While yields were extremely low, there were significant differences in yields related to mulch treatments (Table). Spring bell pepper production has had problems the last several years and this year was no exception. Several growers in the area plan not to grow bell pepper again due to poor overall performance on black plastic. Where climatic conditions get hot quickly, organic mulches may be the best means to increase production. BELL PEPPER PRODUCTION ON DIFFERENT MULCHES COMPARED TO BARE GROUND. Treatment Plant stand Strip harvest Graded harvest 116 DAP lb./acre lb./acre Bare Ground 14b 172b 103b Black Plastic 26a 416ab I 17b Hairy Vetch 25a 708a 890a Rye 31a 416ab 915a Crimson Clover 27a 757a I 121a Rye (adj. N) 27a 684a I 388a Numbers within a column followed by the same letter are not signifi- cantly different at P<0.05. NITROGEN SOURCES AND RATES FOR BELL PEPPER PRODUCTION Beth Guertal and Randy Akridge Slow-release nitrogen (N) materials are often used to reduce N leaching losses from sandy soils and extend N availability over a growing season. Because of high cost, slow-release N materials are usually reserved for use in high value production systems such as with turf and horticultural crops. Previous studies have also shown that preplant applications of sulfur-coated urea (SCU) produces yields of vegetables equal to those observed with split applications of soluble fertilizers. Advances in fertilizer technology have produced a new type of slow-release fertilizer - urea coated with a polyolefin resin (PCU). Unlike other slow-release mate- rials, where nutrient release may be controlled by water solubility of the material, microbial decomposition, or diffusion through an impermeable coating, release of nutrients from resin-coated materials is controlled by the moisture permeability of the resin coating and soil tem- perature. Since these are relatively new materials, research which examines the use of resin-coated N fertil- izers in vegetable production systems is scarce. Since previous research has shown that preplant applications of SCU may produce yields equal to split applications of soluble materials, it was our objective to determine if similar results could be obtained with these new resin- coated fertilizers. The three-year experiment was located on a Benndale fine sandy loam in Brewton, AL. Green bell peppers ('King Arthur') were grown on raised beds cov- ered with white plastic polyethylene mulch with drip irri- gation. Eight-week-old transplants were planted into dou- ble rows of 25 foot long plots with within- and between- row spacings of 12- and 24-inches, respectively. The experiment consisted of N rates and N sources, with each rate/source treatment repeated four times. Selected N sources were: (1) sulfur coated urea - 39-0-0 (N-P-K), (2) ammonium nitrate - 34-0-0, and, (3) polyolefin resin-coated urea - 40-0-0. Nitrogen rates were 80, 120, 160, or 200 lb N/acre. An additional zero N control treatment was included, for a total of 13 treat- ments in the study. For the slow-release N sources (sul- fur- and resin-coat ureas) all of the fertilizer was applied in a preplant broadcast application, with fertilizer incor- porated into the planting bed during fumigation and planting bed construction. To simulate application of a soluble N source via fertigation, twenty percent of the ammonium nitrate was applied as a preplant broadcast 14 ALABAMAAGRICULTURAL ExPERIMENT STATION I 1998 FRUIT AND VEGETABLE RESEARCH REPORT 15 application, with the remaining N applied every other week in five equal applications. In each year of the study both N source and N rate affected some component of fruit quality and total marketable pepper yield. Typically, yield of each grade of pepper increased quadratically with increasing N rate, maximizing somewhere between 120 and 200 lb N/acre. Total marketable yield of pepper was maximized at 204, 110, and 118 lb N/acre in 1995, 1996, and 1997, respec- tively. Thus, in two of three years yield was maximized near the AU recommended N rate of 120 lb N/acre. When examined as a percent of total yield (non-marketable + marketable) N source rarely affected the partitioning of harvested peppers into grade groups. Adding N from any N source decreased percent non-marketable (cull) yield and increased the percentage of marketable yield that was large (US # 1) peppers. This effect was observed in all three years of the study. In 1995, total marketable yield of peppers grown in SCU was equal to that of the unfertilized check, and less than total marketable yield with PCU or AN treatments. In 1996, yields were the same for each N source, and those yields were all greater than yields obtained without N. In 1997 yield of green pepper grown with ammonium nitrate at 80 lb N/acre was lower than from either of the slow- release N sources. At that N rate there simply may not have been sufficient soluble N continuously available for crop uptake and growth precisely when plant need was greatest. At the recommended rate of 120 lb N/acre yield of pepper from all sources was equal. As N rates increased above 120 lb/acre yields decreased with PCU but remained constant for SCU and AN. In conclusion, there were few differences in pep- per yield or quality due to N source, except in 1995 when peppers grown in SCU had a yield as low as those from unfertilized plots. In this preliminary experiment, it appears that preplant slow-release N fertilizers may be a viable alternative for vegetable crop production. PICKING METHODS AFFECT YIELD, GRADE DISTRIBUTION, AND RETAIL VALUE OF COLORED BELL PEPPER Eric Simonne, John Owen, and Christine Harris Green peppers usually cost between 69-99 cents per pound whereas colored bell peppers cost between $1.99 and $5.99 per pound. Colored bell peppers and green bell peppers have similar production requirements. Yet, most of the colored bell peppers sold in the state are imported from Florida, South America, or Holland. Bell pepper varieties with unusual colors include yellow ('Valencia'), orange ('Oriole'), and red ('King Arthur'). In addition, bell peppers can also be black ('Black Bird'), brown ('Chocolate Bell'), purple ('Blue Jay'), or white ('Ivory') in color. Most bell peppers are green at the immature stage and come to full color during ripening. Consequently, it takes a few more days to har- vest a colored bell pepper as compared to the mature green ones. Color changes in bell pepper can be induced in stor- age by exposing them to ethylene, but this practice is not common in Alabama. Because of this, bell pepper growers have to leave the fruit on the plant three to five extra days in order to develop 1/3 color. Therefore, colored bell pep- pers need to stay longer on the plant, thus increasing the risk of mechanical damage and sunscald. This study was designed to determine if yield, grade distribution, and retail value of colored bell pepper was affected by picking bell pepper at different levels of development. Selected varieties were 'Bell Star', 'Capistrano' (green to red varieties), 'Goldcoast', and 'Admiral' (green to yellow varieties). The peppers were grown from trans- plants on bare ground with drip irrigation in 22-feet long, single-row plots at the Piedmont Substation in Camp Hill, Alabama. Fertilization consisted of 70-70-100 N-P 2 0 5 - K 2 0 applied preplant and 10 lb. N as Ca(NO 3 ) 2 sidedressed every other week. The picking methods were 0/3 colored (mature green, by size), 1/3 colored (by size), and 2/3 col- ored (by size). Treatments picked "by size" correspond to 1998 FRUIT AND VEGETABLE RESEARCH REPORT 15 16 ALABAMA AGRICULTURAL EXPERIMENT STATION commercial standards. The peppers were harvested 15 times between June 24 and November 28 and graded. Early yields were affected by picking method. Early marketable yields were 7,641 lb./acre for 'Admiral', 7,168 lb./acre for 'Bell Star', 5,227 lb./acre for 'Goldcoast', and 4,673 lb./acre for 'Capistrano'. No sig- nificant difference was shown between total marketable yield among varieties. The average total marketable yield was 28,409 lb./acre for each variety. Total fancy yields ranged between 8,481 lb./acre for 'Bell Star' and 12,733 lb./acre for 'Goldcoast'. THE EFFECTS OF PICKING MET Bell pepper grade Method Total marketable yield distribution, yield, and (lb./acre) retail value did respond 0/3 colored 32,363 t1/3 colored 28,042 significantly to picking 2/3 colored 25,438 method (Table). A large I Retail value based on $1.99/Ib for percentage of the early 2 Retail value based on $5.99/Ib for HO marketable yield of each variety was graded as fancy (71% for 'Goldcoast', 68% for 'Admiral' and 'Capistrano', and 49% for 'Bell Star'). As expected, yield decreased as the fruits were allowed to develop color due in part to the increased risk of sunburn with prolonged time on the plant. Using $0.99 and $1.99 as expected retail value for green and colored bell peppers, respectively, resulted in retail val- ues of $32,039, $55,803, and $50,621/acre for each picking method (0/3, 1/3, and 2/3 colored, respectively). These results suggest that although yields of colored bell peppers D ON RETAIL VALUE AND YIELD. may be lower than those of Fancy yield Total retail value green bell peppers, the (lb./acre) (US $) higher expected prices for 5,394 $10,788' the colored stages of bell 4,076 $24,4562 2,353 $14,118 pepper make up for the fancy grade peppers. fancy grade peppers. lower yield. ALTERING SIZE AND YIELDS OF IRISH POTATOES Joe Kemble,Arnold Caylor, and Tony Dawkins Last year, we reported on a study that examined the effect of in-row spacing on yields of Grade B Irish potatoes ("Small potatoes can bring big returns"). In that study, we reported that by decreasing in-row spacing, potato growers can produce more Grade B sized potatoes. At the 4 inch spacing, 51.5% of the total marketable yields were Grade B potatoes (131.44 CWT/acre). With the exception of 1998, many Alabama potato growers were receiving a premium for Grade B potatoes (1.5-inch mini- mum diameter to 2.25-inch maximum diameter). These smaller potatoes are often sold as "new potatoes" to restaurants and grocery store chains. Results from 1997 were promising, but we need- ed to repeat this study. In 1998, this study was conducted at the North Alabama Horticulture Substation (NAHS) in Cullman and also at the Sand Mountain Substation (SMS) in Crossville. In March, seed of the red-skinned Irish pota- to 'LaRouge' was planted into furrows at five different in- row spacings: 4, 6, 8, 10, and 12 inches. As a result, the number of seed pieces increased with decreasing in-row spacings. The narrowest in-row spacing, 4 inches, required three times as many seed pieces as the 12-inch spacing (the 12-inch spacing is presently the conventional spacing used by growers). At both locations, Irish potatoes were grown in accordance with accepted guidelines for producing Irish potatoes in Alabama. There were few insect and disease problems at either location likely due to the dry, hot sum- mer weather that began in early May. Potatoes were har- vested in early July at NAHS and in the beginning of August at SMS. Due to elevated soil temperatures and little rain- fall, yields were considerably lower that expected at NAHS. Yields were an average of 60% lower at NAHS compared to SMS and as a result only yield data from SMS is presented here. Overall, yields were lower in 1998 than in 1997. This can be attributed to higher than normal air and soil temperatures and lack of rainfall that occurred from early May until harvest. Soil temperatures higher than 85 0 F can inhibit tuberization in Irish potatoes and thus yields are reduced. In 1998, yield of Grade A, B, C or total marketable tubers did not differ significantly at any 16 ALABAMAAGRICULTURAL ExPERIMENT STATION I 1998 FRUIT AND VEGETABLE RESEARCH REPORT 17 in-row spacing. In 1997, the total weight of Grade B potatoes increased with decreas- ing in-row spacings. It was found that more Grade B tubers were produced at the 4-inch in-row spacing (131.4 CTW/acre) than at any other spacing. However, in 1998, this was not the case. No statistical differences were observed at any in-row spacing although there was a trend towards / a higher percentage of Grade B potatoes as in-row spacing decreased as in 1997. We will repeat this study next year and hope for a better, less stressful growing season. I HE EFFECT OF IN-ROW SPACING ON YIELD COMPONENTS OF 'LAROUGE' IRISH POTATO AT SAND MOUNTAIN SUBSTATION. Grade distribution (CWT/acre) Total marketable In-row spacing A B C yield% 4 99.9 53.4 5.4 158.7 6 83. 1 47.5 7.2 137.8 8 96.6 53.1 6.7 156.4 10 110.0 47.7 6.2 163.9 12 91.0 42.5 6.8 140.3 Total marketable yield is calculated as the sum of A, B, and C grade potatoes. 2 Percent Grade B potatoes is of the total marketable yield DESPITE THE WEATHER - THE IRISH POTATOES LAROUGE AND NDO 2686-6R PERFORMED WELL Joe Kemble,Arnold Caylor, and Tony Dawkins The Irish potato industry struggled a great deal in 1998. Early in the season, excessive rain prevented many growers from planting on-time. By the time the spring floods were turned off at the start of May, the heat was turned on. High soil temperatures inhibited tuberization throughout much of the potato acreage. Yields were down and quality was an issue. Many growers complained of poor storage life for their potatoes as well as low prices offered to them by brokers. Irrigation would have benefit- ed some growers, but irrigation was not the answer to all of their production problems. Almost 13,000 acre of Irish potatoes were planted in 1998 among Baldwin, Cullman, Dekalb, and Jackson counties. However, only about 12,000 acres were harvest- ed. The poor growing conditions described above were the primary culprits for this reduction in harvested acreage. Last year, we reported on the appearance and per- formance of several selected red-skinned Irish potato cul- tivars grown at the North Alabama Horticulture Substation (NAHS) in Cullman and at the Sand Mountain Substation (SMS) in Crossville. Yields last year were greater at SMS than at NAHS. At SMS, marketable yields of COO 86107- 1 (204.9 CWT/acre), ND 2225 (171.3 CWT/acre), NDO 2686-6R (123.6 CWT/acre), and LaRouge (160.8 CWT/acre) were greater than the other cultivars tested. At NAHS, the marketable yields of ND 2225 (160.6 CWT/acre), Red LaSoda (152.9 CWT/acre), Ida Rose (150.2 CWT/acre), and LaRouge (133.0 CWT/acre) were greatest. At NAHS and SMS, seed pieces of each of ten Irish potato cultivars were sown into plots 40 feet long and 3.5 feet wide. Seed potatoes were provided by Irish pota- to breeding programs in North Dakota, Oregon, and Idaho. Seed pieces were spaced 12 inches apart within the row at the end of March at SMS and in the beginning of April at NAHS. Potatoes were harvested at the start of July at NAHS and in the beginning of August at SMS. Yields at SMS were low due to the conditions described above. Yields did not differ among grades (A=48.0 CWT/acre; B=26.3 CWT/acre; C=5.8 CWT/acre) or for total marketable potatoes (avg.=80.1 CWT/acre) between any of the cultivars tested. However, yields and separations between the different cultivars test- ed were apparent at NAHS (see table below). As in 1997, LaRouge and NDO 2686-6R per- formed well. Approximately 50% of their total marketable yields graded as As. Additionally, NDO 4588-5, NDO 4592-3, and Ida Rose all produced over 100 CWT/acre with most of their potatoes graded as As. Skin color was also measured to determine just Grade B 2 62 56 40 53 49 T _ _ - r - - - _ _ _ I ~ ~l~l~i - C- ~I 1998 FRUIT AND VEGETABLE RESEARCH REPORT 17 18 ALABAMA--- .AGRIC-ULTURAL .-- EXPERIIMENT-4'1 S%01TAT%1 %Iv how red each cultigen was as com- pared to the others. This was mea- sured with an instrument that quantified the redness of the skin. Ratings below reflect how close the skin color of each potato was to true red (i.e., how intense the redness of each potato was). As you move down the list, the skin colors became lighter red. Most red to the least red: Ida Rose, COO 86107-1R, LaRouge, NorDonna, NDO 4592-3, ND 2225-1R, NDO 2686-1R, ND 5084-3R, NDO 4300-1R, NDO 4588-5. YIELD AND GRADE DISTRIBUTION OF SELECTED IRISH POTATO CULTIVARS AT NAHS. CWT/acrel Total marketable 2 Total yield 3 A B C Cull LaRouge 189.1 203.6 109.8 58.3 21.1 14.5 NDO 2686-6R 170.1 186.2 93.8 53.1 23.1 16.1 NDO 4588-5 146.8 160.5 46.2 76.9 23.8 13.7 NDO 4592-3 122.4 135.0 67.5 32.3 22.6 12.5 Ida Rose 110.0 114.4 68.6 31.9 9.4 4.4 NDO 4300-IR 99.3 100.7 27.0 38.6 33.7 1.5 COO 86107-I R 84.2 96.2 43.3 32.6 8.4 12.0 ND 2225-I R 80.0 84.0 29.0 30.4 20.6 4.0 NorDonna 79.5 83.2 23.3 29.3 26.9 3.7 ND 5084-3R 42.0 43.8 14.3 16.4 11.3 1.8 LSD 4 77.2 76.9 48.3 33.4 26.3 II CWT/acre = 100 lb/acre 2 Total marketable yield is calculated from the sum of weights for A, B, and C grade potatoes. 3 Total yield is calculated as the sum of weights for total marketable yield and cull. 4 Least significant difference (P<0.05). IRRIGATION INCREASED YIELD OF IRISH POTATO Eric Simonne,Arnold Caylor, and Christine Harris Approximately 13,000 acres of Irish potato are harvested in Alabama each year. Yet, most of this produc- tion is done without irrigation. Thirty-year rainfall aver- ages for Alabama show that approximately two to three inches of rain can be expected monthly between March and July. These dates correspond to the period of Irish potato production. While average water supply from rain may seem adequate for Irish potato production, it is not uncommon for spring rains to provide more than one inch of water in one single day, followed by two to three weeks of drought. The effects of uneven rainfall are more pro- nounced on sandy soils than on heavy-textured soils because of a lower soil water holding capacity. Irrigation scheduling is used to determine when to irrigate and how much water to apply. When daily water use is calculated from class A pan evaporation and cumu- lated over several days, it is possible to use the water bal- ance method to schedule irrigation of Irish potato. While limiting the number of calculations to perform, this method adjusts water application to crop age, actual rain- fall, real-time water use, and soil type. The objective of this study was to evaluate the effect of irrigation on Irish potato yield under two N fertilization rates using a water budget to schedule irrigation. In this study, water use was calculated by adjust- ing class A pan evaporation to crop age and calculated over several days. Adequate corrections were made for rainfall. Irrigation practices used were done according to the "checkbook method" and were adjusted to actual daily weather conditions (class A pan evaporation, rainfall), crop age, and soil type. The checkbook method calculates the quantity of water available to the crop by counting as "Income" factors those factors that add water to the root zone (rain and irrigation) and as "Expenditure" factors those factors that remove water from the root zone (crop evapotranspiration, deep percolation, run-off). The check- book method actually calculates a daily balance, for an account expressed in gallons of water/acre. Irish potatoes were planted at North Alabama Horticulture Substation in Cullman in 1996, 1997, and 1998. Seed pieces of 'Red LaSoda' were planted in 20- foot single row plots at one-foot within row spacing on April 9, 1996; March 12, 1997; and April 7, 1998. Cultural practices were similar each year and followed current rec- ommendations for commercial Irish potato production. Seven controlled irrigation levels were created by accu- rately controlling the rate and time of irrigation from the drip tapes placed on each bed. A treatment with no irriga- 18 ALABAMA AGRICULTURAL ExPERIMENT STATION ........................... rip 1 198FUI.N.EGTBE EERH EOTI7 tion was used as a control. Potatoes were harvested 85 days after hilling (DAH) in 1996, 70 DAH in 1997, and 82 DAH in 1998 and graded as U.S. Extra #1 ("A"), U.S. #1 ("B"), U.S. #2 ("C"), and cull. In 1997, 21 consecutive days with rainfall in June for a total of 26- inches of rainfall induced water move- /ment in excess of field capacity and no irrigation was used. Consequently, the effect of irrigation could not be evalu- ated that year. Interaction between irrigation and N rate was not signifi- cant for 1996 and 1998. In 1996, five irrigation events were applied between 35 and 60 DAH and 7 irriga- tion events between 33 and 64 DAH in 1998. Each year, irrigation significant- ly influenced total and marketable tuber yield. Total, marketable, and U.S. Extra #1 yields responded qua- dratically to irrigation in both 1996 and 1998 (Figure). N levels did affect yield in 1996 and 1998. In both years, higher yields were reported under the high N treatment. In 1996, marketable yield averaged 23,000 lb./acre for the high N treatment and 21,000 lb./acre for the low N treatment. Marketable yield in 1998 averaged 16,800 lb./acre (high N) and 14,400 lb./acre (low N). The results of this study suggest that supplementing rainfall with irrigation can increase Irish potato yields during dry years. Also, adjusting irrigation to actual class A pan evaporation and rainfall may increase potato yields. Effect of irrigation on Irish potato yield at North Alabama Horticulture Station in 1998. Yield Ibs./acre 30,000 I- 100 120 140 1600 20 40 60 80 Irrigation rate Effect of irrigation on Irish potato yield at North Alabama Horticulture Station in 1996. '-1--- -- '-~~ ---- I I U 1998 FRUIT AND VEGETABLE RESEARCH REPORT 19 r 20 ALABAMA AGRICULTURAL "EXPRIMENTv1 STATIONV OPTIMIZING IN-ROW SPACING FOR Joe Kemble and Arnold Caylor Sweetpotatoes are a mainstay of vegetable pro- duction in Alabama. In 1998, almost 14,000 acres of sweetpotatoes were grown in Alabama. With conventional production practices, sweetpotato slips are spaced 12 inch- es apart within rows with 3 to 31/2-feet between rows. At this spacing, most sweetpotato varieties produce a higher percentage of US #1 roots compared to Canners, Jumbos, or Culls. Last year at North Alabama Horticulture Substation (NAHS), the variety Beauregaurd produced 176 CWT/acre of US #1 roots accounting for 58% of the total marketable yield. NC 93-17, a variety from the breeding program at North Carolina State University, produced good quality roots with nice skin and flesh, but most of the roots were Canners. A study was initiated at NAHS to evaluate the effect of increasing in-row spacing on root size of NC 93- 17 in order to determine if by increasing in-row spacing, a higher percentage of US #1 roots could be produced. Slips of NC 93-17 were planted into the field in June at 5 different in-row spacings: 12-, 14-, 16-, 18-, and 20-inch in-row spacings with three feet between rows. Sweetpotatoes were harvested and graded in the end of August. Statistically, there were no differences in yield between any of the in-row spacings (see table below). However, yields of NC 93-17 in 1998 were greater than those in 1997. In 1997, NC 93-17 produced 50 CWT/acre US #1's, 48.8 CWT/acre Canners, 33.2 CWT/acre Culls, and 100.4 CWT/acre total marketable yield. In 1998, NC 97-13 produced more US #1 roots than Canners or Culls. US #1 root yields were between 66 and 71% of the total marketable yield compared to approximately 50% in 1997. Why the difference in 1998? It is likely that the hot, dry summer of 1998 was more conducive to sweet- potato production than the wet, overcast, and rainy season of 1997. This study will be repeated in 1999 with wider in-row spacings as well as those tried in 1998. YIELD AND GRADE DISTRIBUTION FOR NC 93-17 AT 5 IN-Row SPACINGS AT NAHS. CWT/acre I Spacing US # I Canner Cull Total Total US #14 marketable 2 yield 3 % 12-inch 279.1 63.7 64.7 342.8 407.5 68 14-inch 279.9 110.0 34.0 389.9 423.9 66 16-inch 325.3 112.5 25.4 437.8 463.3 70 18-inch 293.4 80.3 39.0 373.7 412.7 71 20-inch 255.2 65.8 39.2 321.1 360.3 71 II CWT/acre = 100 lb/acre 2 Total marketable yield is calculated from the sum of weights for US #1 and Canner roots. 3 Total yield is calculated as the sum of weights for total marketable yield and cull. 4 Percent US #1: calculated by dividing weight of US #1 by the total marketable weight. SWEETPOTATO YIELD RESPONSE TO IRRIGATION AT Two NITROGEN RATES Eric Simonne, Edgar Vinson, III, Christine Harris, Jim Bannon, Jason Burkett, and Marvin Ruf Sweetpotato is grown extensively in the southern United States as a dry-land crop. Although sweetpotato is considered to be a moderately drought-tolerant crop, recent research reports found that sweetpotato yields may be increased with irrigation. The objectives of this study were (1) to determine if sweetpotato yields respond to irri- gation under the growing conditions of Alabama and test an irrigation scheduling model for sweetpotato and (2) to determine any interaction of irrigation and nitrogen (N) fertilization on sweetpotato yield. This experiment was conducted at E.V. Smith Research Center (EVSRC) and Sand Mountain Substation SWEETPOTATOES 20 ALABAMAAGRICULTURAL ExPERIMENT STATION I 1998 FRUIT AND VEGETABLE RESEARCH REPORT 21 (SMS) in 1997. Preplant fertilization consisted of 20-0-20 (N-P 2 0 5 -K 2 0) at a rate of 440 lb./ acre (448 kg/ha) at EVSRC and 3-15-30 (N-P 2 0 5 -K 2 0) at a rate of 200 lb./acre (224 kg/ha) as broadcast on June 27 at SMS. An additional 600 lb./acre (672 kg/ha) of 13-13-13 was applied one day after establishment (DAE) at SMS. Selected varieties were 'Beauregaurd' at EVSRC and 'Georgia Jet' at SMS. Slips were planted on June 20 and 27, 1997, respectively (DAE = 0). At both locations, total nitrogen (N) fertilization (preplant + sidedress) was 120 and 150 lb./acre (132 and 165 kg N/ha) for the low N and high N treatments, respec- tively. Low N treatments corresponded to the medium rec- ommended rate. Sweetpotatoes were harvested October 21 (122 DAE) at EVSRC and October 9 (103 DAE) at SMS and graded as U.S. #1, Canner, Jumbo, and Cull. Eight (at EVSRC) and seven (at SMS) irrigation rates were created by a line-source irrigation system consisting of a single row of closely spaced sprinklers. Irrigation regimes ranged between 0% and 140% of the model rate providing uniform water applications parallel to the line (along a bed) and decreasing water applica- tions perpendicular to the line (from the line to the out- side row). A treatment with no irrigation was used as a control. Soil water tension was measured at an 8-inch depth with gypsum blocks. In our study, water use was calculated by adjust- ing class A pan evaporation to crop age and cumulated over several days. Class A pan evaporation was adjusted using a variable crop factor developed in South Georgia for 'Georgia Jet'. This crop factor allowed a maximum soil water tension of 25 centibars (25kPa). Adequate cor- rections were made for rainfall. We scheduled an irriga- tion when cumulative water use exceeded the soil mois- ture reserve in the root zone. The amount of irrigation water applied was equal to the cumulative water use. Total rainfall was 11 inches at EVSRC and 13.5 inches at SMS. Under the weather conditions of 1997, the model called for 11 irrigation events at both loca- tions. Total irrigation applied was 10.34 inches at EVSRC and 7.6 inches at SMS. The effect of irrigation was similar at both N rates. No significant difference was shown between N treatments. At both locations, US #1 sweetpotato yields were not affected by irrigation (Figure). A similar result was observed with marketable and total yield at SMS. At EVSRC, a significant yield increase was observed with the high-water irrigation rate; however, this was due to an increase in Canner and Cull weights. The readings of the gypsum blocks showed that soil water tension seldom dropped below 40 kPa. The yield and soil water tension data together suggest that the irrigation schedule followed maintained too low a soil water tension. Because this work was conducted on small plots, excessive water benefited the "dry" treatments more than the "wet" treatments. It is possible that sweetpotato will benefit from irrigation under an irrigation scheduling model that allows a higher maximum soil water tension. Marketable yields for both locations did show a significant difference between the low and high N treatments. Marketable yields averaged 19,520 and 25,000 lb./acre (low N) and 18,960 and 26,000 lb./acre (high N) for EVSRC and SMS, respectively. Before using irrigation scheduling, growers should evaluate the economical ben- efits of irrigation and start with a small test acreage. 0 20 40 60 80 100 120 140 160 Irrigation gradient, pct. Effect of irrigation on sweetpotato yield at E.V. Smith Research Center. Yield, Ibs./acre 50,000 Total yield 40000 [- Market yield O Extra U.S.#1 yield 30,000 - 10,000 I I I I I I I I 0 20 40 60 80 100 120 140 160 Irrigation gradient, pct. Effect of irrigation on sweetpotato yield at Sand Mountain Substation. 1998 FRUIT AND VEGETABLE RESEARCH REPORT 21 EVALUATION OF BOTRAN FOR PLANT BED DISEASE CONTROL OF SWEETPOTATOES Edward Sikora and Jim Pitts This experiment was conduct at the Chilton Area Horticultural Substation in Clanton, Alabama, during the summer of 1997. The test was conducted to evaluate the effectiveness of a low rate of Botran for controlling plant bed diseases as compared to its standard rec- E ommended use rate. The test consisted of four treatments, replicated five times, in a ran- Treatment/rat domized complete block design. Each repli- cation consisted of 10 roots of the sweetpota- 3.75 lb/14 to 'Beauregaurd' which were placed into a of water/I bucket and covered with weathered (three- 2. Botran 75" years-old) sawdust. Treatments are as out- 1.25 Ib/141 lined below. After 68 weeks, the percent of water/I sprouted tubers and the number of 3. Mertect 8 oz/7.5 ga sprouts/tuber were determined, of water The treatment consisting of the high 4. Untreated rate (3.75 lb.) of Botran resulted in the high- Based on tot est number of sprouts per healthy tuber and 2 Total numbe the highest number of sprouts overall. Both Botran treat- ments produced a higher number of sprouted tubers (due to a lower incidence of tuber rot disease) than the Mertect treatment and the untreated control. FFECT OF BOTRAN AND MERTECT ON DISEASE DEVELOPMENT Pct. Avg no. Total no. te Application sprouted sprouts on sprouts 2 method tubers healthy tuber (50 tubers) WP Bed spray 3 90.0 10.1 458 gallons 000 sq. ft. WP Bed Spray 92.0 7.4 343 gallons 000 sq. ft. Seed dip 84.0 8.0 338 lions control - 80.0 7.5 302 tal number of sprouts from tubers that sprouted (non-diseased) r of sprouts from the 50 tubers bedded over all replications. sprayed over sweetpotatoes before covering them with sawdust. EVALUATION OF FUNGICIDES FOR CONTROL OF EARLY BLIGHT ON TOMATO Edward Sikora,Arnold Caylor, Mahefa Andrianifahanana, and Derenda Hagemore In 1998, a variety of fungicides were evaluated for their ability to control early blight on tomato. This exper- iment was conducted at the North Alabama Horticultural Substation in Cullman, Alabama. The products Penn- cozeb 75 DF, Vondoflo 4F, Quadris and Cuprofix were evaluated alone or in various combinations at different time intervals with the more established compounds, Kocide 2000 and Bravo Weatherstik. The tomato cultivar 'Sun Leaper' was used in the trial. Disease severity was determined July 7, 14, 21, and 28, 1998. Tomatoes were harvested weekly and total yield was determined (data not available at printing). Early blight pressure was high based on the amount of disease observed in the unsprayed control plots (93.8% on 7/28). More early blight was observed on the unsprayed control compared to the fungicide treatments on all rating dates. Two treatments, (1) Penncozeb plus Kocide early followed by Quadris alter- nated with Penncozeb for the remainder of the season, and (2) Penncozeb plus Bravo Weatherstik full season, provided the best control of early blight among all the treatments tested. Differences were most obvious on the July 28 rating date. 22 ALABAMAAGRICULTURAL ExPERIMENT STATION I 1998 FRUIT AND VEGETABLE RESEARCH REPORT FUNGICIDE EVALUATION TRIAL;WEEKLY DISEASE (EARLY BLIGHT) SEVERITY RATINGS Treatment % Early blight (rate/acre) 7/7 7/14 7/21 7/28 Unsprayed control 7.8 34.0 65.4 93.8 Vondoflo 4F 3 pt/A + Kocide 2000 2 Ib/A 1 followed by Vondoflo 4F 4.5 pt/A** 1.4 7.6 13.8 32.8 Penncozeb 75 DF 2 lb/A + Kocide 2000 2 Ib/A* followed by Penncozeb 75 DF 2 Ib/A 2 1.2 7.0 13.2 30.6 Cuprofix 6 Ib/A 1.2 7.0 13.6 28.0 Cuprofix 4 Ib/A 1.2 6.6 12.2 29.8 Penncozeb 75 DF 2 Ib/A + Bravo Weatherstik 1.5 pt/A 1.2 5.0 7.8 13.2 Penncozeb 75 DF 2 Ib/A + Kocide 2000 2 Ib/A 1 followed by Quadris 6 oz/A alternated with Penncozeb 75 DF 3 lb/A 2 1.0 3.6 5.6 9.8 t Applied the first three weeks only. 2 Applied over the remainder of season. All treatments applied on seven- to 10-day intervals. TOMATO IPM PROGRAM A SUCCESS IN ALABAMA IN 1998 Edward Sikora, Geoff Zehnder, Joseph Kemble, Mahefa Andrianifahanana, and Michael Patterson In 1998, the Alabama Tomato IPM Program was successfully demonstrated for the second consecutive year through large scale on-farm demonstrations with five cooperating growers in Geneva county. A one-acre tomato field was set aside by each grower for the purpose of com- paring the Alabama Tomato IPM Program with their stan- dard calendar-based pest program and general production practices. The IPM program consisted of a twice-a-week insect/disease scouting program combined with TOM- CAST (a weather-based fungicide spray program). The TOM-CAST program was provided by the Agricultural Weather Information Service (AWIS) which is a private weather provider located in Auburn, Alabama. The most significant disease problems to develop in 1998 were tomato spotted wilt virus (TSWV) and the fungal disease southern blight. Thrips, vectors of TSWV, and fruit worms were the most damaging insect pests. There were no apparent differences in tomato yield, disease severity, or insect pressure between the IPM and the calendar-based pest program field sections. All the growers involved in the project claimed they saved money on pro- duction costs by reducing pesticide applications when fol- lowing the IPM program. On average, growers made four fewer fungicide applications when following the TOM- CAST weather-based fungicide spray program. The reduc- tion in fungicide use was as much as 46 percent in one grower's IPM section. On average, growers following the recommendations of the IPM field scout made 10 fewer insecticide applications compared to their standard, calen- dar-based spray program. Two growers reduced insecticide usage by over 70% by following Auburn's IPM guidelines. A research component of the grant evaluated the efficacy of flame cultivation, mechanical cultivation, mulching, and various combinations of these practices in okra, pepper, sweet corn, and tomato production systems in Alabama. Most treatments worked well with okra, pep- per, and sweet corn, but preliminary results indicate that flame cultivation in a tomato production system may not be feasible due to the growth habit of the crop. A handbook outlining the IPM program is cur- rently being developed and will be made available to all interested parties in 1999. 23 EVALUATION OF PENNCOZEB FOR CONTROL OF SEPTORIA LEAF SPOT ON TOMATO Edward Sikora,Arnold Caylor, and Derenda Hagemore This experiment was conducted at the North Alabama Horticultural Substation in Cullman, Alabama, in fall, 1997. Penncozeb 75WP was evaluated in a tank- mix with Kocide 2000 or Bravo 720, and in an alternating spray program with Bravo 720. Cuprofix was also includ- ed in the test along with an unsprayed control treatment. Fungicide applications were made at seven to 10 day inter- vals beginning three days after transplanting. Disease severity ratings were taken on September 26, October 2, October 13, October 21, and October 27, 1997. Harvest data were not available due to an early frost. Septoria leaf spot was the most common problem in the test plot. Low levels of early blight occurred but only on the control treatment. Significantly more Septoria leaf spot was observed on the unsprayed control treatment at all rating periods compared to the fungicide-treated plots. The Penncozeb + Kocide tank-mix and the Cuprofix had significantly less disease than the Bravo + Penncozeb tank-mix on the last rating date (10/27). PENNCOZEB -TOMATO EVALUATION TRIAL;WEEKLY DISEASE SEVERITY RATINGS, CULLMAN, AL, 1997 Treatment I Rate/acre Disease (Septoria leaf spot) severity rating 10/2 10/9 10/20 10/27 1. Penncozeb 75DF + 2 Ib Kocide 2000 2 Ib 0. Ob 3.0b 4.5b 5.7c 2. Bravo 720 + 0.75 pt applied until Penncozeb 75DF 1.0 Ib fruit set then Bravo 720 + 1.5 pt Penncozeb 75DF 2.0 lb 0.Ob 4.Ob 8.2b II .7b 3. Bravo 720 alternated 2 pt applied until with Penncozeb 75DF 2 lb fruit set then Bravo 720 alternated 3 pt with Penncozeb 75DF 3 Ib 0.2b 3.5b 6.2b 7.5bc 4. Cuprofix 6 lb 0.5b 1.7b 3.7b 5.5c 5. Unsprayed control 9.5a 22.0a 39.7a 46.7a I Means followed by the same letter are not significantly different. 24 ALABAMA AGRICULTURAL ExPERIMENT STATION 1998 FRUIT AND VEGETABLE RESEARCH REPORT RESPONSES OF FIELD-GROWN TOMATOES TO NITROGEN SOURCES Beth Guertal and Joe Kemble The effect of different nitrogen (N) sources on crop growth and production has long been a topic of inter- est among scientists. Reasons for selecting a certain N form may be environmental, such as using positively- charged ammonium forms to reduce leaching losses; may be economic, when a cheaper form of N is selected; or may be quality/quantity issues, when one form of N pro- duces a better crop than another form. Often, the source of fertilizer N becomes a nitrate (NO3-) versus ammonium (NH 4 +) issue. Often, green- house or hydroponic studies reveal that many plants are sensitive to ammonium, and ammonium toxicity may be observed. However, in field studies the impact of NH 4 +-N nutrition on vegetable crop growth and yield is less clear. Thus, the objective of this study was to examine the effect of N source (nitrate versus ammonium) on field-grown, drip-fertigated stake tomato production yield and quality. The two-year experiment was located at the E.V. Smith Horticultural Research Unit, near Shorter, Alabama on a Norfolk fine sandy loam. Tomatoes ('Mountain Pride') were grown on six-inch raised beds covered with black plastic polyethylene mulch with drip irrigation installed. Six-week-old transplant were planted into single rows of 25-foot long plots with a within row spacing of 24 inches. Nitrogen sources were treatments, each repeated four times. Selected N sources were: (1) calcium nitrate (Ca(N0 3 )2 - 16-0-0 (N-P-K), (2) urea (CO(NH 2 ) 2 - 45-0- 0), (3) ammonium nitrate (NH4NO3 - 34-0-0), (4) urea- ammonium nitrate solution (UAN - 32-0-0), and (5) potassium nitrate (KNO 3 - 13-0-39). A total of 180 lb. N/acre was applied with each N source, with 25% (45 lb. N) applied as a preplant/pre-mulch broadcast treatment and the remaining N applied as 10 weekly applications of 13.5 lb. N/acre. Weekly N applications, beginning one week after transplanting, were applied through drip irriga- tion system. If an N source also supplied K (e.g., KNO 3 ) or Ca, the amount of that nutrient applied in the N treat- ment was also applied to the other N source treatments. Plant height and stem diameter were affected by N source. In 1995 and 1996 tomato plants that received N as UAN were shorter with smaller stem diameters (1996) at all sampling dates. There were few other differences in plant size or stem diameter due to N source. In both years, there were few significant differences in leaf-N concen- tration due to N source. In the first sampling of 1995, tomato leaves from plots receiving UAN had a higher N concentration than those receiving KNO 3 . Whole plants from UAN treatments were shortest at this time, so vol- ume of plant tissue may be the cause of this higher N con- centration. In this limited study (one site, two years) yield and quality of field stake tomatoes grown on raised beds with drip irrigation was only slightly affected by the type of N source applied through the drip irrigation line MARKETABLE AND NON-MARKETABLE TOMATO YIELD AS AFFECTED BY N SOURCE AND HARVEST DATE IN 1996. Harvest date N source Early season Mid season Late season Total Marketable Yield (Ib.lacre) Ca(N0 3 ) 2 1,717aI 9,846b I,198b 12,761c KNO 3 I,296a 17,360a 6,704b 25,360a NH4NO 3 I,198a 16,988a 5,668b 23,854ab Urea 907a I 6,648a 6,802b 24,357ab UAN Ob 2,397c 12,097a 14,494bc Non-marketable Yield (lb.Iacre) Ca(N0 3 ) 2 138al (7.4)2 3,336ab (25.3) 850b (41.5) 4,324b (25.3) KNO 3 275a (17.5) 4,834a (21.8) 2,397ab (26.3) 7,506a (22.8) NH4NO 3 235a (16.4) 3,320ab (I16.3) 2,478ab (30.4) 6,033ab (20.2) Urea 186a (17.0) 3,668ab (18.1) 2,065ab (23.3) 5,919ab (19.6) UAN 49a (100.0) 955c (28.5) 3,466a (22.3) 4,470b (23.6) IWithin each date and quality category,a number followed by the same letter is not significantly different from other numbers in that column with the same letter(s) 2 Numbers in parentheses are non-marketable yield expressed as a percent of total yield. (Table). Although plants grown in UAN were shorter and had reduced early yield (1996 only) than plants receiving other N sources, total yield of tomato was not affected by the UAN treatment. There were few differences in yield and quality of unmarketable fruit due to N source. In this study, it appears that any of the N sources Ca(NO 3 ) 2 , UAN, Urea, KNO 3 , or NH 4 NO 3 would make suitable N sources for tomato production when total marketable yield is a primary concern. 25 r 26 NEW HOT SET TOMATO CULTIVARS -OBSERVATIONS FROM THE FIELD Joe Kemble and Dan Porch It is likely that in several years, most new tomato cultivars will be hot set hybrids, or called Heat-set, or Heat tolerant hybrids. Most of you are familiar with one of the first commercially available hot set tomatoes 'Solar Set' which originated from the tomato breeding program at the University of Florida. Why will most of the cultivars be hot set toma- toes? The unique aspect of hot set tomatoes is that they tend to perform well not just under high temperatures and humidity typical in the Southeast in the summer, but also under cool, rainy environments. Symptom of heat stress such as reduced fruit set, misshapen fruit, and blossom- end rot become apparent when day temperatures exceed 86 0 F and night temperatures exceed 720 F. Hot set toma- toes are better able to handle stressful growing conditions. So, many of the new cultivars such as 'Sun Leaper' set well under more difficult growing conditions. Many new hot set tomato hybrids are introduced each year. As a grower, make a point to evaluate several of these new cultivars in your operation. Try growing a small plot 30 to 40 plants of each cultivars. If you are growing several crops, evaluate these cultivars with each new crop. In this way, you will get a clear idea of how well each of these new cultivars performs during several growing sea- sons under your management. We evaluated several new hot set tomato hybrids during the summer of 1998 on three farms in Blount coun- ty. Seed was provided by Asgrow Seed Co., Novartis Seeds, Inc.-Rogers Brand, and the fresh-market tomato breeding program at North Carolina State University. Transplants were set in the field in the beginning of July. Average daily temperatures exceeded 90 0 F during July and most of August. Below are some observations con- cerning some of the best performing hybrids. NC 96378 from N.C. State. NC 96378 produced firm red fruit that are uniform green and the pedicels are jointed. Fruit have a glossy finish with a deep red color. The blos- som scars are small and pinpoint. Crown fruit set is above average producing mostly extra large to large sized fruit. Fruit were very uniform in size and shape. Plants were one week earlier than 'Solar Set.' Overall, the foliage cover is good, but not excessive. NC 97295 from N.C. State. NC 97295 is a plum or Roma type of fresh-market tomato. The pedicels were jointed with uniform green fruit. Fruit shape was consistent and uniform. The fruit developed a deep red color and glossy finish. The fruit were firm with a pinpoint blossom end and very few fruit produced any noticeable nipples on the blossom end. The foliage cover was good and not excessive. The plant set a great deal of fruit and appears to be a heavy producer. Solar Set from Asgrow Seed Co. Solar Set has been a stan- dard for summer production from Baldwin to Blount County. Solar Set produces jointed pedicels, with uniform green fruit. In this test, the fruit set was good throughout the plant and fruit had smooth blossom scars with good fruit shape. Fruit ranged from extra large to large in size. Canopy cover was adequate but size was not as good as with NC 96378. Florida 47 from Asgrow Seed Co. Florida 47 is fast becoming the standard in Florida. A few growers in South Alabama have tried it out. Florida 47 produces jointed pedicels, uniform green fruit with a good glossy finish. In this test, the crown set was fair to good. Florida 47 set fruit up throughout the plant. The canopy cover of Florida 47 is heavy compared to Solar Set, but not too excessive. Sun Leaper from Novartis Seeds Inc. Sun Leaper pro- duces smooth, glossy fruit with jointed pedicels. The blos- som scars were small with fruit that were mostly extra large to large in size. Crown set was very good and continued throughout the plant. Good foliage cover. Overall, fruit size tended to be larger than any other hot-set tomato in this trial. Suncrest from Novartis Seeds Inc. Suncrest produces jointed pedicels and fruit with green shoulders. The crown set of Suncrest was good but not as good as that of Sun Leaper and Florida 47. The foliage cover was good. The plant type was more vigorous than that of the other hot-set tomatoes above. FT 6116 from Notaries Seeds Inc. FT 6116 is not yet com- mercially available but should be in the next few years. This hot-set tomato looked great. Fruit size was mostly extra large to large. Fruit were uniform green and pedicels were jointed. The crown set was above average. The blossom scars were very smooth. Fruit set was consistent through- out the plant. The plant type was similar to that of NC 96378-not too vigorous, but more than adequate. ALABAMAAGRICULTURAL ExPERIMENT STATION A COMPARISON OF DUMAS-N AND KJELDAHL-N FOR THE DIAGNOSIS OF N NUTRITION IN VEGETABLES Eric Simonne, Christine Harris, and Harry Mills Foliar analysis is routinely used to assess the nutritional status of fast-growing vegetable crops and make fertilization recommendations. The nitrogen (N) sta- tus of a vegetable crop is one important aspect examined through foliar analysis to determine a crop's nutritional needs. The most common method for interpreting N status in vegetable crops is to compare the results of a N analyt- ical assay to published (Kjeldahl N) sufficiency values. With recent advances in N analyzers, the Dumas method may replace the traditional Kjeldahl method for the rou- tine diagnosis of N in plants. In addition, the protocol used to determine Kjeldahl N (Kn) involves acids and heavy metal catalysts, whereas the Dumas method does not. Kn recovers all the protein N, amino N, and an unknown frac- tion of nitrate N in the plant. In contrast, Dumas nitrogen (Dn; also referred to as combustion N) recovers all N frac- tions in the plant including protein, nitrate, and free amino acids. Since these two methods recover different N frac- tions, substantial numerical differences in N data may be observed between both analytical methods. If Dumas N data is interpreted with the presently used Kn-based thresholds, it is possible that these differences change the diagnostic of the N nutrition of that sample. Because developing new threshold values for the interpretation of Dumas N data would be tedious and cost- ly, several attempts have been made to estimate Kjeldahl N from Dn in plants, and then interpret the N nutrition with already published thresholds. Depending on crop type and main N form (nitrate or ammonium) in the fertil- izer schedule, the N-NO3 fraction may represent up to 1.2% of the N in tissues of vegetables. Therefore, this study was conducted to (1) determine the Kn:Dn ratio for vegetable crops, and (2) evaluate the effect of the size of the NO 3 fraction on the Kn:Dn ratio. Leaf samples were taken from vegetable variety trials conducted by the Alabama Agricultural Experiment Station at ten locations scattered throughout Alabama. Collectively, these locations are representative of a wide range of growing conditions and cultural practices. Kn, Dn, and nitrate-N were determined on approximately 130 samples representing most vegetable crops of economi- cal importance in the Southeast (muskmelon, bell pepper, cucumber, eggplant, Irish potato, okra, sweet corn, sum- mer squash, southern pea, sweetpotato, tomato, and watermelon). Overall, Kn may be estimated from Dn with high confidence as Kn=0.75 Dn. As expected, Dn was numeri- cally greater than or equal to Kn. On average, Kn only rep- resented 75% of Dn. On a limited number of samples, however, Dn was less than Kn. This was attributed to ana- lytical errors. Without any adjustments, the diagnosis of N nutrition using Dn data and Kn-based sufficiency thresh- olds will result in an over rating of the N nutrition. In such cases, samples may be rated 'excessive' when N level is in the upper part of the sufficiency range. Similarly, samples with N levels slightly below the sufficiency level (and actually within the hidden hunger range) may be diag- nosed 'sufficient'. Nitrate-N was poorly correlated with Kn - Dn or Kn/Dn, thereby suggesting that differences in Kn and Dn values of the same sample are not only due to the recovery rate of the nitrate-N fraction. These results suggest that when NO 3 -N is not known (as in most routine samples), Kn may be estimated from Dn as Kn = 0.75 Dn. Growers should be aware of what methodology was used to deter- mine N when reading and interpreting results of foliar analyses. 1998 FRUIT AND VEGETABLE RESEARCH REPORT 27 Location of Participating Research Units LAUDERDALE LIMESTONE MADISON JACKSON COLBERT FRANKLIN MORG MARSHALL DE KALB LAWRENC SMS MARION hWINSTON AH c BLOUNT WALKER CALHOUN SAINT CLAIR JEFFERSON LAMAR FAYETTE TALLEDEGA CLEBURNE SChilton Area Horticulture Substation (CAHS) at Clanton, BBE.V. Smith ReCOOSArch Center (EVSRC) at Tallassee, CHILTO GREENE HALE CA 'UMTE PERRY ELMORE LEE AUTAUGAt the commitment of would not have been preseARENGO nted in a timely manner OWNDES IOCTAW BULLOCK DALLAS BARBOUR CLARKE WILCOX BUTLER PIKE Expeimen Fil B)atBetn Gl os Sbtto