1996 Fruit and Vegetable Research Qeport October 1996 Research Report Series No. 12 Alabama Agricultural Experiment Station Dr. James. E. Marion, Director Auburn University, Alabama _ Contents Authors ...................................................................... ...... 1 Problems in Accessing Commercial Markets for Fresh Fruits and Vegetables ................................................................................................ ... 2 New and Profitable Crops for Alabama -- Asparagus ................................................................... 3 For the Second Time, 'Silver Queen' Not Rated as Best-tasting Sweet Corn .............................................................................................. 4 Sensory Evaluation of Alabam a Lettuce ......................................................................................... 5 Effect of Irrigation and Nitrogen Fertilization on N Level in Bell Pepper Leaves ............. ............................................................... 6 Year Two: Double-cropping Bell Peppers and Broccoli on Black Polyethylene Mulch ................................ .......................................... 7 Root Growth Helps Schedule Irrigation for Plastic-Mulched Tomatoes and Bell Peppers ....................................................................... 8 Mulch Color Affects Bell Pepper Yield ..................... ........................................................... 9 Surveying Irish Potatoes for Three Viruses ......................... ....................................... 9 Appearance and Performance of Selected Red-skinned Irish Potatoes ..................................................................................... 10 Could Irrigation Increase Irish Potato Yields in Alabam a? ....................................................... ........................................ 11 Evaluation of Fungicide Treatments to Control Late and Early Blight in Irish Potatoes ............................................................................................... 12 Transgenic Tomatoes Withstand CMV Epidemic ........................................................................ 13 Alabama's Fresh-market Tomato Growers Use Integrated Pest M anagem ent .................................................................................................. 14 Evaluation of Biological Control Treatments for Bacterial Spot Control on Tomatoes ................................................................................ 15 Reproduction of Reniform Nematodes on Snap Beans Commonly Grown in Alabama ............................ ...................................... 16 Molecular Markers in Watermelon .......... ....... ..................................................... 17 Isozyme Markers in Kiwifruit ..................................................................................................... 17 Effect of Mulch Color on Strawberry Production using Annual Hill Plasticulture .......................................................................................... 18 Frost Protection of Satsumas with Microsprinkler Irrigation ................................................................................................ 19 New Peach Thinning Material Evaluated ..................................................................................... 20 Maximizing Irrigation in Peach Production ............................................................................... 20 Evaluation of Fungicides for Scab and Glomerella Control on Pecans ............................................................................................. 21 Evaluation of Fungicides for Pecan Scab Control in Central Alabama ............................................................................................... 22 Evaluation of New Pecan Cultivars for Scab Resistance .......................................................... 23 Yield and Kernel Percentage of 22 Pecan Cultivars from 1992-1995 ...................................................................................... 24 Weed Control Increases Yield and Economic Return from Young 'Desirable' Pecan Trees .................................................. 25 Information contained herein is available to all without regard to race, color, sex, or national origin. October 1996. Authors John Adrian Professor AU Agricultural Economics and Rural Sociology Randy Akridge Superintendent Brewton Experiment Field Paul Backman Professor AU Plant Pathology Jim Bannon Director E.V. Smith Research Center Ellen Bauske Extension Associate AU Horticulture Bobby Boozer Area Horticulturist Chilton Area Horticulture Substation James Brown Associate Professor AU Horticulture Arnold Caylor Interim Superintendent North Alabama Horticulture Substation Cindy Chanrnell-Butcher Research Technician AU Horticulture Fenny Dane Assistant Professor AU Horticulture Bill Dozier, Jr. Department Head AU Horticulture David Dubois Visiting Scholar AU Horticulture Joe Eakes Associate Professor AU Horticulture Ron Eitenmiller Professor Food Science and Technology University of Georgia Wheeler Foshee Extension Associate AU Entomology Bill Goff Professor AU Horticulture Bob Goodman Associate Professor AU Agricultural Economics and Rural Sociology Gary Gray Assistant County Agent Chiltion County Michael Guerini Graduate Research Assistant AU Plant Pathology Beth Guertal Assistant Professor AU Agronomy and Soils Derenda Hagemore Secretary North Alabama Horticulture Substation David Himelrick Professor AU Horticulture Hongwen Huang Associate Professor Wuhan Institute of Botany Chinese Academy of Sciences Joe Kemble Assistant Professor AU Horticulture Stephen Kiser Graduate Research Assistant AU Agricultural Economics and Rural Sociology Leonard Kuykendall County Agent Chambers County Pauline Lindo Graduate Research Assistant AU Agronomy and Soils Karrie Lovins Research Technician AU Plant Pathology Ronnie McDaniel Associate Superintendent Gulf Coast Substation Harry Mills Professor Horticulture, University of Georgia John Murphy Assistant Professor AU Plant Pathology Monte Nesbitt Area Horticulturist Gulf Coast Substation John Owen Superintendent Piedmont Substation Mike Patterson Associate Professor AU Agronomy and Soils Jim Pitts Superintendent Chilton Area Horticulture Substation Billy Rhodes Professor Horticulture, Clemson University Marvin Ruf Interim Superintendent Sand Mountain Substation Laura Sanders Computer Specialist AU Discrete and Statistical Sciences Ed Sikora Associate Professor AU Plant Pathology Lynn Slocum Research Technician AU Horticulture Amy Simonne Postdoctoral Fellow AU Nutrition and Food Science Eric Simonne Assistant Professor AU Horticulture Jim Smith Agricultural Technician Turnipseed-lkenberry Place Lewis Tapley County Agent Jackson County Ed Tunnell County Agent Coordinator Baldwin County Larry Wells Interim Superintedent Wiregrass Substation Rudy Yates, Jr. Assistant County Agent Dallas County Geoff Zehnder Professor AU Entomology Xian Zhang Visiting Scholar AU Horticulture 2 ALABAMA AGRICULTURAL EXPERIMENT STATION Problems in Accessing Commercial Markets for Fresh Fruits and Vegetables JOHN ADRIAN AND STEPHEN KISER A frequently heard comment among Alabama's fruit and vegetable growers is, "We can grow it, but we can't sell it." AAES research evalu- ated this professed dilemma to provide some insight into the problem. Goals were to determine and evaluate differences and compatibilities between produce growers and marketers in the state. Forty-two marketers and 64 growers were personally interviewed to determine their role in and opinions of the fruit and vegetable system. About three-fourths of the fresh-produce-purchasing firms contacted were retailers, while the balance was equally represented by brokers and wholesalers. About two-thirds of these firms were proprietorships, while 21% and 14% were corpora- tions and partnerships, respectively. Product specifications most frequently de- sired by retailers for local produce were fresh, clean, appropriately packaged and vine-ripe products. Al- though retailers stated a desire to use more locally grown products, they indicated that market require- ments and conditions were rigid and some local pro- ducers would have difficulty meeting them. Sev- eral considerations that influence the marketers' willingness and ability to purchase locally grown crops were identified. The most strongly stated fac- tor related to provision of the desired quality of pro- duce; difficulty in providing an adequate volume was second in importance. Retailers stated that pro- ducers generally could not provide a dependable level of supply for a sustained period; one or two deliveries were generally not adequate to establish an account with a grower. Another consideration was the retailers' hesitation to interrupt or decrease the flow of a product from normal channels. Loss of "good will" with present suppliers could ad- versely affect future product flows to the firm. Even with these recognized difficulties, retailers believed that local producers could favorably market their products through retail outlets in the future. About two-thirds of the producers noted a strong orientation toward direct markets; 57% sold through farmers markets, and 31% used roadside stands or pick-your-own operations. Four percent and 3%, respectively, indicated an orientation to- ward brokers and wholesalers/retailers. The primary reason for using a particular outlet was convenience (53%). Other reasons noted for selecting a particu- lar market were: only market available (18%), owner of retail outlets (7%), large volume required to use the market (6%), repeat sales (5%), and bet- ter prices (3%). The top-two problems associated with markets used were insufficient buyers and low price. Fifty-four percent of producers stated that price received at markets used was unsatisfactory. On the buying side of the market, firms are interested in handling locally grown produce, but generally on a basis that is consistent with normal sourcing terms and conditions. Basically, retailers or their warehouse units can operate without locally grown produce, but under appropriate conditions, their business could be enhanced by availability of quality locally grown crops. Retailers want stabil- ity in product flow or, at least, sufficient lead time to promote items that are readily available. On the selling side of the market, growers in the state are primarily oriented toward direct mar- kets, which seem to become saturated with prod- ucts during the primary production season, result- ing in low prices and unsold products. Many pro- ducers lack sufficient volume of quality produce to access commercial outlets. Facilities are also often insufficient to handle produce so as to maintain quality or package product in appropriate form. Post-harvest handling of produce is often as impor- tant as production methods in determining the qual- ity of a product and its shelf life. Future growth of Alabama agriculture could be greatly influenced by better coordination be- tween growers and marketers and better informa- tion about requirements to access commercial mar- kets. Coordination can be improved through con- tracting, cooperative organizations, and leadership by key individuals throughout the state. Alabama growers need to understand that the commercial produce system can exist without them, but they will have difficulty moving volume without the sys- tem. If producers can help brokers, wholesalers, and retailers be profitable, they will enhance their chances for success in the commercial sector. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 3 New and Profitable Crops for Alabama -- Asparagus JOE KEMBLE, ERIC SIMONNE, JIM PITTS, JIM BANNON, AND ARNOLD CAYLOR There are many possibilities for growers in Alabama. Many small and part-time growers in Alabama, who truck farm, have roadside stands, or sell their vegetable crops wholesale, rely on more traditional vegetable crops, such as southernpeas, collards, and watermelons for the bulk of their production and profit. Sometimes, a nontraditional approach can really pay off. Al- though not a traditional part of the southern diet, asparagus is becoming more common on dinner plates in Alabama. Presently, little asparagus is grown in Ala- bama. Most of the asparagus sold here is grown in California, Washington, Michigan, and vari- ous islands in the Caribbean. As well as being valuable from a nutritional standpoint, asparagus also demands a high wholesale price. Alabama's unique climate and growing areas should be well suited to asparagus production. In order to explore the feasibility of aspara- gus production in Alabama, three sites were se- lected to establish asparagus plantings. Trans- plants of 'Jersey Giant,' an all-male hybrid, were planted in 1996 at the E.V. Smith Research Cen- ter in Shorter, Chilton Area Horticulture Substa- tion in Clanton, and North Alabama Horticulture Substation in Cullman. 'Jersey Giant' has shown good adaptation and consistent, high yields throughout many regions of the U.S. The term "all-male" refers to the fact that there are male and female asparagus plants. Female plants pro- duce smaller spears than male plants, and they produce seeds that can germinate and form vol- unteers. An all-male cultivar such as 'Jersey Gi- ant' is more tolerant of diseases and produces large, high-quality spears. It will take three seasons for the asparagus to become fully established. After this point, the plantings can be subjected to a variety of treat- ments. This is also the point at which a commer- cial grower would begin harvesting. Once estab- lished, an asparagus planting can last more than 15 years if proper care is provided. In other parts of the country where aspara- gus is grown, weeds tend to be the greatest pro- duction challenge. Initially, most of the AAES research will focus on weed control, using more novel devices such as a flame-cultivator in com- bination with new herbicides to control weed problems. Research will also focus on the use of row covers to blanch (whiten) developing aspara- gus spears. Blanched asparagus commands a higher price in the fresh-market, but has a very limited market acceptance. Over the next several years, the perfor- mance of the plantings will be monitored for dis- ease and insect problems. In 1998, yields and quality data will be collected. The first year is the most critical for establishing young trans- plants, and to date plantings at each location are off to a great start with no major insect or disease problems being observed. 4 ALABAMA AGRICULTURAL EXPERIMENT STATION For the Second Time, 'Silver Queen' Not Rated as Best-tasting Sweet Corn AMY SIMONNE, ERIC SIMONNE, JIM PITTS, AND GARY GRAY 'Silver Queen' may be losing its status as the most-preferred sweet corn variety. AAES taste tests conducted in both 1995 and 1996 found that 'Silver Queen' was not rated as the best-tasting variety. In 1995, a white sweet corn taste test was organized at the Chilton Area Horticultural Sub- station (CAHS) in Clanton. The primary objec- tive of the taste test was to determine if 'Silver Queen' was actually recognized for its own at- tributes or if it benefited primarily from "name recognition." Among nine cultivars of sweet corn evaluated, 'Silver Queen' was ranked the seventh. These results prompted some skepticism from "sweet-corn connoisseurs," so the taste test was conducted again in 1996. A taste-test experiment of white sweet corn varieties was organized at the CAHS in the same manner as in 1995. Cooked ears from the CAHS sweet corn variety trial were served to a panel of 100 tasters. A total of nine varieties were evalu- ated, but each panelist was asked to rate a selec- tion of only five cultivars. Each five-sample set included 'Silver Queen,' along with four other va- rieties. Samples were coded by random three-digit numbers. The panelists were first asked to list all the sweet corn variety names they could remem- ber, then they were asked to rate appearance of the sweet corn ears. Af- ter rating of appearance, 1996 the panelists were asked to taste the sweet corn Variety (type) S sou and rate for sweetness, flavor, and overall pref- Snow White (sh2) ........ Harris Silverado (se) ............... Harris erence. Panel members Starshine (se)................ Senecz were mainly growers, FMX 413 (sh2).............Ferry- Fantasia (se) .................. Asgro, gardeners, and retirees. Treasure (sh2) .............. Harris Ratings of appear- Snow Belle (se)............ Asgro Rising Star (se) ............ SeedNW ance, sweetness, flavor Silver Queen (su)......... SeedW and overall preference 'Varieties were rated on a 0-1 differed significantly 2 The types of sweet corn are s cultivars have 5-15% sugar at among varieties (see 3 Overall rank sum was calcula table). Most of the se- smaller the overall rank sum, lected cultivars received acceptable ratings. The appearance of 'FMX 413' was rated best, while 'Snow White,' 'Treasure,' 'Snow Belle,' and 'Sil- ver Queen' were rated the lowest. The sweetness of 'Snow White' was the highest; whereas, 'Ris- ing Star' and 'Silver Queen' were the lowest. Fla- vor rating was highest in 'Silverado' and was low- est in 'Silver Queen.' Results revealed that 'Sil- ver Queen' was not ranked among the top-five varieties; it was ranked ninth for overall prefer- ence. Further, only 6% of panelists could correctly identify 'Silver Queen' in 1996, as compared to 30% in 1995. Major changes from last year's re- sults occurred in 'Treasure,' which dropped from a 1995 overall ranking of first to a 1996 overall ranking of fifth. Snow White's overall rankings improved in 1996 from eighth in 1995, to first. All the top-five varieties in all attributes are ei- ther sugar-enhanced or supersweet sweet corn. In both years, 'Silver Queen' was located on the bottom scale in all attributes. These results emphasize the importance of cultivar selection. Producers should constantly look for the ever-changing new cultivars or new releases in order to improve their production. Rankings from this study should by used in con- junction with yield performance and disease re- sistance before selecting a white sweet corn. SWEET CORN SENSORY EVALUATION 1 ed Overall Visual Sweetness Flavor Overall rce preference appeal rank sum 3 Seeds 10.0 6.8 10.4 8.4 10 Seeds 9.4 8.2 9.9 9.0 10 a 9.2 9.0 9.0 7.3 14 Morse 8.1 9.7 10.0 6.8 14 w 8.0 8.6 7.8 7.3 19 Seeds 7.5 6.7 8.3 7.7 22 w 6.6 6.5 7.5 8.1 26 Vay 6.2 7.5 4.9 5.1 30 Vay 5.6 6.7 4.2 5.8 33 4 scale (0 = Undesirable/Dislike; 14 = Desirable/Like Extremely). ugary (su), sugar enhanced (se), and supersweet (sh2). Typically, su harvest; se, 8-20%; and sh2, 25-40%. ted by adding the ranks of each attribute (Maximum value = 36); the the better. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 5 Sensory Evaluation of Alabama Lettuce AMY SIMONNE, ERIC SIMONNE, JOHN OWEN, LARRY WELLS, AND RON EITENMILLER It is often said that lettuce grown in Ala- bama is too bitter because of the weather. How- ever, an AAES sensory evaluation of various let- tuce varieties revealed that acceptable quality and good-tasting lettuce can be grown in Alabama. Most of United States' annual 205,000-ton lettuce crop is grown in California. Although let- tuce is a popular crop in home gardens, no com- mercial production exists in Alabama. Main types of lettuce commercially available are (1) iceberg (head lettuce), (2) Romaine, (3) butterhead, and (4) leaf lettuce. Head lettuce is more difficult for home gardeners to raise; whereas, leaf lettuce is harder for stores and restaurants to keep. In addi- tion to variation in head shapes, lettuce with dif- ferent foliage colors from traditional greens also are available. Most people are familiar with ice- berg lettuce because it is commonly sold in stores, but leaf lettuce is commonly grown by home gar- deners. Because the harvestable part of lettuce is a rosette of leaves, any foliar damage caused by in- sects, viruses, and fungi reduces marketability. The main objective of lettuce breeding programs is to produce lettuce resistant to several viruses and diseases, as well as tip burn. Resistant genes from wild Lactuca lettuce species are often used as sources of resistance to viruses and other dis- eases. However, incorporating resistant genes from L. saligna or L. virosa often lead to increased levels of sesquiterpene lactones, which are known as bitter compounds. Little information exists on the relationship between bitterness and sesquit- erpene lactones levels. Commercially available lettuce varieties were grown at the Wiregrass Substation (WS) and Piedmont Substation (WS) following current fer- tilization and pest control recommendations. At maturity, it was hand-harvested, washed, and cut into bite-size pieces about the size used in tossed salad. Different types of lettuce were served one by one to a group of 15 trained panelists. Panel- ists were trained prior to the tasting session. The training session consisted of providing each pan- elist with a series of caffeine solutions with in- SENSORY EVALUATION OF BITTERNESS IN LETTUCE VARIETIES' Variety Mean Most Lowest Highest (location) score frequent Epic (WS) ........... ....... 1.6 1 0 6 Salinas (WS) ..................... 1.6 0 0 4 Nevada (PS)...... ......... 2.0 0 0 9 Red Prize (WS) ................. 2.2 2 0 7 Legacy (WS) ............. 2.3 1 0 7 Sierra (PS) ................. 2.5 2 0 7 Nancy (WS) ............... 2.9 3 0 10 Red Salad Bowl (WS) ...... 3.2 0 0 11 Brunia (PS) ........................ 3.3 1 0 10 Cabernet Red (WS)..........3.5 2 1 13 Parris Island (WS)............3.6 3 0 14 Slobolt M.I. (WS).............3.8 2 0 10 Optima (WS)..........4.1 2 0 12 Optima (PS)..........4.9 0 0 13 Greeng (WS) ............. 5.2 5 1 15 Nancy (PS) ... 4 0 15 Big Curly (PS)..................9.3 13 0 15 Slobolt M.I. (PS) ........... 10.1 15 1 15 'The lower the score, the less bitter the lettuce. creasing bitterness and their corresponding bit- terness rating (0%=0, 0.05%=2, 0.08%=5, 0.15%=10, and 0.20%=15). Hence, when the trained panelists were used, it was possible to quantify panelist response in numeric scores. Pan- elists were instructed to calibrate their taste us- ing the caffeine solutions between each sample. Mean, most frequent, lowest, and highest scores for each lettuce variety and growing loca- tions are presented in the table. Scores varied considerably between panelists. Although signifi- cant differences between varieties were found, 34% of the lettuce varieties were rated lower than a score of 7. Most prevalent scores were less than 4, suggesting that the lettuce was not very bitter, if at all. Depending on the individual, bitterness scores of less than 7 would be considered accept- able, panelists reported. Panelists did not reject red or purple lettuce. Growing conditions seemed to affect bitterness scores. This study suggests that it is possible to grow non-bitter, pleasant-tasting lettuce in Ala- bama. Future studies will focus on determining the impact of cultural practices and harvest dates on sensory attributes of lettuce. 6 ALABAMA AGRICULTURAL EXPERIMENT STATION Effect of Irrigation and Nitrogen Fertilization on N Level in Pepper Leaves ERIC SIMONNE, PAULINE LINDO, JOE EAKES, AND HARRY MILLS Maintaining adequate moisture and nutrient lev- els to maximize yields are the primary objectives of irrigation and fertilization of fast-growing crops such as bell peppers. Commonly, irrigation is used when plants begin to wilt or when the soil feels dry. Pep- pers fertilized according to current recommendations typically receive a total of 120 pounds of nitrogen (N) per acre, 30-40 pounds of which are preplant incor- porated. The remaining N is sidedressed at rates of 20 pounds of N applied approximately every two weeks. An AAES study was conducted to determine if Foliar N concentration (%) 6- * 0 W 5 - O Low N * High N 4 L 3 I 6- 0 H 5 0 S 4 L 3 25 75 125 Irrigation (%) Nitrogen Concentrations (percent N, on a dry-weight basis) in bell pepper leaves sampled on 62 (top) and 84 (bottom) Days After Transplanting (DAT) as Affected by Rates of Nitrogen Fertilizer and Irrigation. applications of N at current recommended rates main- tain plant N status at levels that do not restrict bell pepper yields. 'X3R Camelot' peppers were grown on bare ground at the Horticulture Unit of the E.V. Smith Research Center following recommended cultural practices. Irrigation was applied overhead and sched- uled by using an irrigation scheduling model based on daily pan evaporation (See "Response of Bell Pep- per Yields to an Irrigation Scheduling Model" in the AAES Research Report Series No. 11 for more informa- tion). Fertilization consisted of a "standard" sidedress application (per acre) of 15 pounds of N and a "high" rate of 30 pounds of N applied on 6, 11, 20, 44, 58 and 72 days after transplanting (DAT) as calcium nitrate. On 62 DAT (harvest of first bloom) and 84 DAT (after five harvests), leaf samples were taken by pull- ing 30-40 of the most recently, fully mature leaves of each plot. Samples were processed for nutrient analy- ses, and N concentration was determined by complete combustion with a Leco FP-428 N analyzer. Irrigation rate, fertilization rate and harvest date significantly affected foliar N concentration. At 62 DAT, foliar N levels were similar for both N rates, and all foliar N concentrations were above the 3.5- 5.0% deficiency range (see figure). At 84 DAT, foliar N concentrations in plants receiving the recommended rate were significan--tly lower than those in plants re- ceiving the high-N rate. Irrigation at rates above 75% of the model rate reduced foliar N levels, although the lowest foliar N level was still well in the suffi- ciency range. These results suggest that the "high-N" rate maintained higher foliar N concentrations after five harvests than the recommended N application rate. The results of this one-year study suggest that current N fertilization recommendations maintain foliar N lev- els at non-limiting values for bell pepper production. However, because after five harvests, foliar N con- centrations began to decline, current recommended rates may not provide adequate N in growing situa- tions that allow for a larger number of harvests. Tak- ing leaf samples during the harvest period may pro- vide real-time information on bell pepper N status. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 7 Year Two: Double-cropping Bell Peppers and Broccoli on Black Polyethylene Mulch JOE KEMBLE, BOBBY BOOZER, AND JIM PITTS Despite the potential for greater yields of high-quality produce, Alabama growers have ex- pressed concern over the high costs of producing vegetables on polyethylene mulch with drip irri- gation (plasticulture). Polyethylene mulch and drip irrigation lend themselves to double-crop- ping. This can allow material and labor costs as- sociated with plasticulture to be spread over two growing seasons. To date, there are no commer- cial recommendations for double-cropping veg- etables in Alabama. An AAES study is examining the effects of various fertility levels and mulch types on yield of double-cropped bell peppers and broccoli. This study is examining the production costs and eco- nomic returns for the various double-crop sys- tems. 1996 marks the second year of this three- year study at the Chilton Area Horticulture Sub- station in Clanton. Bell peppers grown on black polyethylene (plastic) covered plots with fertility levels rang- ing from 0-240 pounds of N per acre were com- pared to the conventional treatment, which is 120 pounds of N per acre on bare ground. Plants in bare-ground plots received additional nutrients via sidedressing, while bell pep- BELL PEPPER YIE pers on black- Treatment U.S. Fancy plastic plots re- 1995 1996 ceived nutrients lb./a. lb./a. via fertigation. O N....................1,018.7 399.6 Fertilizer was in- 60 lb. N ............ 2,320.9 1,665.8 120 lb. N .......... 4,804.8 4,258.7 jected weekly af- 180 lb. N..........4,417.3 4,332.3 ter transplanting 240 lb. N..........5,454.2 1,668.0 and continued Bare ground.....2,621.9 2,883.1and continued through final harvest. Moisture levels were moni- tored with switching tensiometers placed in a rep- resentative plot of each treatment. After final har- vest, plants were sprayed with the herbicide glyphosate, allowed to die back, and then re- moved. After two spring crops of the pepper 'Marengo,' total marketable yields were higher for the 120 pound per acre N treatment than for all of the other treatments (see table). Generally, yields in 1996 were higher than in 1995, likely due to more favorable growing conditions. Note that yields generally decreased when more than 120 pounds per acre were applied to the bell pep- pers. This indicated that more fertilizer is not al- ways better and in fact can be harmful to market- able yields and especially quality. Decreased yield was more apparent in 1996 than in 1995. Appli- cation of more fertilizer than is required is also costly from an economic standpoint as well as for time and labor. Hurricane Opal, combined with poor grow- ing conditions in the fall of 1995, caused the first fall broccoli crop to fail. In 1996, broccoli was transplanted the first week of September. LDS BASED ON 1995 AND 1996 YIELD DATA U.S. #1 Total marketable Total yield 1995 1996 1995 1996 1995 1996 lb./a. lb./a. lb./a. lb./a. lb./a. lb./a. 2,624.0 2,716.1 6,728.3 6,101.3 7,908.9 7,605.2 5,397.5 5,030.0 12,277.7 10,906.5 13,455.9 12,613.8 7,525.8 7,589.1 16,653.1 18,247.6 18,112.1 20,809.5 7,501.7 6,663.2 15,962.4 16,285.2 17,179.6 18,855.1 6,994.2 3,655.4 16,744.9 10,279.4 18,283.3 12,934.9 6,112.9 6,692.7 11,437.8 15,701.9 12,755.7 17,625.0 8 ALABAMA AGRICULTURAL EXPERIMENT STATION Root Growth Helps Schedule Irrigation for Plastic-Mulched Tomatoes and Bell Peppers ERic SIMONNE, DAVID DuaoIs, AND JiM BANNON In order to estimate the maximum amount of water accessible to roots during the development of tomato and bell pepper plants grown on black- plastic with drip irrigation, AAES researchers at the Horticulture Unit of the E.V. Smith Research Cen- ter examined the rate of root system expansion for these plants. This amount of water represents the highest volume that should be applied in one irriga- tion if no leaching is desired. 'Celebrity' tomato and 'X3R Camelot' bell pepper were transplanted onto three-foot-wide, nine-inch-deep raised beds. Tomato plots consisted of single rows of five plants spaced 18 inches apart. Bell peppers were planted on staggered double rows, 14 inches apart, at a 12-inch, within-row spac- ing. The soil type was a sandy-loam soil. Insect and disease control followed cur- rent recommendations. Drip ir- rigation was used to maintain ROOT SYSTEM DE adequate soil moisture. Fertil- AND CORRESI izer was injected weekly at a rate of 10 pounds of N per acre, dev alternately from calcium nitrate and potassium nitrate begin- ning one week after transplant- in g . 4 .................................. On 0, 4, 11, 17, 22, 28, 11 ................................. 17 ................................ 41, 48, 55, 63, and 71 days af- 22 ................................ ter transplanting (DAT), the 28 ............................... depth (vertically), length (hori- 41 ........................... Sr 48 ........................... Sr zontally, in the direction of the 55 ......................... Me bed), and width (horizontally, 63 .......................... Ma perpendicularly to the direction 71 ............................. H of the bed) of the roots were 0 .... ..... measured by destructively dig- 4 .................................. ging a three-foot-long section 11................................ 17 ................................ in the center of each plot. Root 22 ................................ parameters were significantly 28 ............................... 4 1 ............................... different for both crops and 48 ........................... S were affected by digging date 55 ......................... Me (see table). Root systems of two 63 .......................... M 71 ........ ..................... consecutive plants within a row Sandy loam soil wit "overlapped" on 17 DAT for 2 DAT = Days After T bell pepper and 22 DAT for to- 3 L = leaf 4 For a maximum allo' mato. The volume of soil occupied by the roots was determined, and corresponding soil-water-holding capacity for a sandy loam soil was determined as V = 2.4 DAT, where V is maximum irrigation amount (in gallons per 100 feet), for DAT ranging between 15 and 50. At 50 DAT or more, the entire bed vol- ume is occupied, the root system is established, and V = 120 gallons per 100 feet. Before 15 DAT, it is preferable to apply 36 gallons per 100 feet of bed. These results may be incorporated into irrigation scheduling models for vegetables grown on plas- tic-mulch with drip irrigation, because they adjust irrigation amounts to root growth. However, they should be validated and adjusted to soil type before being used with commercially grown tomato or bell pepper. PTH, WIDTH, AND LENGTH OF TOMATO AND BELL PEPPER, PONDING AVAILABLEWATER FOR SANDY LOAM SOILS' Stage of Rooting Rooting Rooting Available elopment' depth width length water 4 in. in. in. gal./l 0 ft. 'Celebrity' Tomato ...L2 2 1 1 0 ...L4 4 2 2 0 ... L4 6 4 5 4 ...L6 5 13 14 21 L9-10 9 20 15 62 Bloom 8 27 15 87 nall Fruit 7 33 15 86 nall Fruit 9 35 15 119 dium Fruit 8 35 15 115 ature Fruit 8 34 15 104 arvest 1 8 36 15 112 'X3R Camelot' Bell Pepper ...L2 2 1 1 0 ...L4 3 2 2 0 ...L4 5 5 6 6 ... L66 17 12 43 L9-10 9 27 12 89 L13-15 8 27 12 85 Bloom 8 31 12 90 mall Fruit 9 35 12 116 dium Fruit 8 36 12 113 ature Fruit 8 37 12 112 larvest 1 8 37 12 108 a 0.15% total soil-water-holding capacity. ransplanting. wable soil water tension of 0.25 bar (25 kPa). 1996 FRUIT AND VEGETABLE RESEARCH REPORT 9 Mulch Color Affects Bell Pepper Yield RUDY YATES JR., JAMES BROWN, BILL GOFF, CINDY CHANNELL-BUTCHER, AND LAURA SANDERS Mulch surface colors have been widely re- ported to influence bell pepper yields; however, re- ports have varied in their conclusions with respect to mulch color effects on yield. A study was con- ducted at the E.V. Smith Research Center in Shorter to determine the effects of plastic mulch surface col- ors on the yield of bell pepper plants. Treatments consisted of six mulch surface colors (black, white, red, aluminum, green IRT-76, and blue) and a bare soil control. A black plastic mulch was applied to the soil in mid-March, along with trickle irrigation tubing and methyl bromide fumigant. After allowing for adequate fumigation, treatments were applied in mid-April. Polyurethane oil enamel paints were used to obtain the alumi- num ("Aluminum 32"), red ("Chinese Red 15"), and blue ("Bermuda Blue 21") mulch surface colors. 'Skipper' bell pepper plants were transplanted into field plots in early April at an in-row spacing of 18 inches, one row per plot. Lime and fertilizer were ap- plied to the soil ac- cording to soil test rec- ommendations prior to treatment applications. The treatments with outstanding market- able values were alu- minum and blue (see table). MULCH COLOR EFFECTS ON BELL PEPPER YIELD Color Marketable yield lb./a. Black .............................. 5,358 White .............................. 7,443 Red ................................ 7,949 Aluminum .................... 10,488 Green (IRT-76) ............. 7,359 Bare ground...................6,942 Blue ................................ 8,796 'Marketable yield is the mean of three harvests: July 8, July 23, and Aug. 7. Surveying Irish Potatoes for Three Viruses MICHAEL GUERINI, JOHN MURPHY, ED SIKORA, LEWIS TAPLEY, AND ED TUNNELL Irish potatoes represent one of the largest vegetable industries in Alabama. Unfortunately, little is known in Alabama about viral disease prob- lems in this crop. Because Irish potato is an early- season crop, it could serve as a reservoir for a num- ber of viruses that infect other crops that are grown throughout the summer. To examine this potential, commercial Irish potato production fields were surveyed for three economically important viruses, cucumber mosaic virus (CMV), potato virus Y (PVY), tobacco etch virus (TEV). These viruses have and can caused serious losses on many other vegetable crops im- portant to Alabama, such as tomatoes, peppers, and watermelons. All three viruses are transmitted by aphids in a nonpersistent manner. The problem with these viruses being transmitted in a nonpersistent manner is that their spread cannot easily be con- trolled by the application of insecticides. Samples were collected from 10 fields in Baldwin County, nine fields in Jackson County, and one field in Cullman County. Most of Alabama's Irish potatoes are grown in these counties. Samples were collected in Baldwin County in late May and from Jackson and Cullman counties in late June. Samples were placed on ice, transported to the labo- ratory, and tested for the presence of the three vi- ruses using a method called ELISA. A total of 251 samples were collected in Baldwin County. PVY occurred most frequently, being detected in 24.7% of the samples (62 of 251). CMV was detected in 17.1% of the samples (43 of 251), while the incidence of TEV was 4.4% (11 of 251). CMV and PVY were detected more often from samples taken from East Baldwin County. In Jackson and Cullman counties, 211 plant samples were collected for analysis by ELISA. PVY was detected in 23.2% of the samples (49 of 211), and CMV in 18.5% of the samples (39 of 211). TEV occurred in 55% of the samples (116 of 211). These results suggest that all three viruses occurred in Irish potato samples taken from the three counties, and therefore, the Irish potato crops could serve as a source of inoculum for other vegetable crops. Next year in addition to assaying for CMV, PVY, and TEV, plants will be tested for potato leafroll virus and potato virus X, two other economi- cally important viruses that infect Irish potatoes grown in other states and Canada. Although ELISA is an excellent tool for detecting the presence of a plant virus; data from the ELISA test can sometimes be somewhat ambiguous. Thus, a second method of analysis of samples will be incorporated into the next survey as a means to confirm the serological analyses (ELISA test). 10 Appearance and Performance of Selected Red-skinned Irish Potatoes JOE KEMBLE, ERIC SIMONNE, ELLEN BAUSKE, ARNOLD CAYLOR, AND MARVIN RUFF The Alabama Irish potato industry has changed a great deal over the past 10 years. An- nually, almost 11,000 acres of Irish potatoes are produced. In past years, most of this production was grown for processing, but now, most of the acreage is devoted to production for the fresh- market (table stock). New research initiatives are underway to identify varieties that perform well in Alabama and are acceptable to retailers and consumers. A cooperative research project with the Irish potato breeding program at North Dakota State University is underway to evaluate selected red- skinned potatoes from the North Dakota program under Alabama's growing conditions. Seven va- rieties were grown at two locations, North Ala- bama Horticulture Substation (NAHS) in Cullman and at Sand Mountain Substation (SMS) in Crossville. Seed pieces were planted in April and harvest in mid-July. Overall yields were greater at NAHS than at SMS (see table). For U.S. "A" and total mar- ketable yields, 'LaRouge' out yielded all other varieties. 'Red Norland' and 'Red Ruby' produced the lowest marketable yield at NAHS, while 'Red Norland' and 'NorDonna' produced the lowest marketable yield at SMS. Skin color, tuber shape, and internal color were also examined after two months in storage at 40 0 F. In terms of most red to least red skin color, the seven varieties ranked in the following order for decreasing redness: ND 2225-1R > Red Ruby > NorDonna > LaRouge > Red Norland > Red LaSoda > Viking at SMS; and Red Ruby > ND 2225-1R > Red Norland > NorDonna > LaRouge > Viking > Red LaSoda at NAHS. Over- all, ND 2225-1R and Red Ruby produced the red- dest skin color, while 'Viking' and 'Red La Soda' produced the poorest and were often more brown in appearance. Tuber shape and internal color seemed to be consistent within a variety at both locations, with the exception of 'Viking,' which tended to produce off-shaped tubers with an off-white in- terior color. 'NorDonna' seemed to suffer from early die back at both locations and produced a great deal of tubers with secondary growth. Most of Alabama's Irish potatoes are grown without the benefit of irrigation, but it is likely that they would benefit from it. Research is be- ing conducted to demonstrate the benefit of supplemental irrigation for the production of Irish potatoes (see "Could Irrigation Increase Irish Potato Yields in Alabama" on p. 11). IRISH POTATO YIELDS BASED FROM NORTH ALABAMA HORTICULTURE SUBSTATION (NAHS) AND SAND MOUNTAIN SUBSTATION (SMS) IN 1996 Variety U.S. "A" U.S. "B" Cull Total marketable NAHS SMS NAHS SMS NAHS SMS NAHS SMS lb./a. lb./a. lb./a. lb./a. lb./a. lb./a. lb./a. lb./a. La Rouge ..................... 17,720 11,715 5,819 1,151 2,240 n/a 24,267 13,037 Red LaSoda ................. 15,682 14,235 2,458 669 3,127 n/a 18,748 15,044 Viking .......................... 14,546 9,366 952 700 2,340 n/a 15,609 10,159 ND 2225-1R ................ 11,233 10,486 5,041 1,525 1,484 n/a 17,230 12,213 Red Norland ................ 11,155 8,277 1,467 545 1,672 n/a 12,883 8,837 NorDonna .................... 10,704 5,476 3,547 1,245 949 n/a 16,212 6,939 Red Ruby ..................... 10,548 10,968 2,551 1.229 3,127 n/a 13,852 12,322 ALABAMA AGRICULTURAL EXPERIMENT STATION 1996 FRUIT AND VEGETABLE RESEARCH REPORT 11 Could Irrigation Increase Irish Potato Yields in Alabama? ERIC SIMONNE, JOE KEMBLE, AND ARNOLD CAYLOR Although Irish potato is classified as a drought-sensitive vegetable crop, it is seldom ir- rigated in Alabama. This practice makes potato yield dependent on rainfall pattern. The objec- tive of this AAES study was to (1) evaluate the effect of irrigation on potato yield, and (2) de- velop a water budget for scheduling irrigation of Irish potatoes. The model uses class A pan evaporation data to determine daily the amount of water used by the crop. In areas where weather data are not readily available or where official data are of lim- ited use because of the presence of a microcli- mate, a calibrated container such as a #2 wash tub, a ruler and a rain gage may be used to collect on-site weather data. The water balance takes into account crop age, soil type, and weather (pan evaporation and rainfall). The model is practical because it provides information on when to start irrigation and how much to apply each time. Seed pieces of 'Red LaSoda' potatoes were planted at a 12-inch within-row spacing on 20- foot long plots on April 9 at the North Alabama Horticulture Substation in Cullman. Soil type was a fine sandy loam with a water-holding capacity of 0.13 inch per inch. Fertilization consisted of a preplant application of 850 pounds per acre of a 5-10-15 fertilizer and two sidedress applications of ammonium nitrate. Because the effect of ni- trogen (N) fertilization is often dependent on water application, the validation included two N rates: 35 pounds of N for the low-N and 50 pounds of N for the high-N rate. Total N fertilization was 120 and 150 pounds of N per acre, for the low and high N treatments, respectively. Insect and pest control practices followed current recommen- dations. Seven controlled irrigation levels were cre- ated by accurately controlling the rate and time of irrigation from the drip tapes placed on each Yield (lb./a.) 30,000 25,000 20,000 15,000 * Total yield 10,000 - 0 Marketable yield , Yields of U.S. Extra #1 and U.S. #1 grades 0 . , I I ' I 175 150 100 50 25 0 Irrigation rate (% of the model) Irish Potato Response to Controlled Water Applications bed. A treatment with no irrigation was used as a control. Potatoes were harvested on July 22 and graded as U.S. Extra #1 and U.S. #1 (diameter >1.9 inch), U.S. #2 (diameter > 1.5 inch) and culls (damaged or diameter < 1.5 inch). The high-N treatment tended to produce higher yields than the low-N treatment, but these differences were not statistically significant. The model scheduled four irrigations be- tween June 17 and July 1. Irrigation significantly influenced total yield, marketable yield, and com- bined U.S. #1 grade (see figure). Differences in culls were not significant. The results of this one- year study suggest that supplementing rainfall with irrigation could increase Irish potato yields. These results also suggest that controlling the amount of water applied by adjusting irrigation to pan evaporation and rainfall may result in higher potato yields. Excessive water, as well as not enough water reduced potato yields. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 11 Evaluation of Fungicide Treatments to Con- trol Late and Early Blight in Irish Potatoes ED SIKORA, ELLEN BAUSKE, MONTE NESBITT, BOBBY BOOZER, ARNOLD CAYLOR, RONNIE MCDANIEL, JIM PITTS, AND DERENDA HAGEMORE Alabama Irish potato growers typically make six or more fungicide applications to their crop during an average growing season to con- trol the fungal diseases early blight and late blight. The most common spray program consists of a protectant fungicide such as Bravo 720 alternated weekly with a systemic/protectant fungicide com- bination such as Ridomil/Bravo 81. Initiation of the spray program during the season varies among growers. Some will make their first fungicide application at plant emergence, while others may wait until plants reach 10 inches in height. The earlier a spray program begins generally means more fungicide applications will be made at greater expense to the grower. Growers, however, who delay their first application may experience higher levels of disease. This study was conducted to evaluate two spray programs that are commonly used in Ala- bama, as well an Integrated Pest Management (IPM) program based on disease scouting. The experiment was conducted at the North Alabama Horticulture Substation in Cullman, Chilton Area Horticulture Substation in Clanton, and Gulf Coast Substation in Gulf Shores. Treatments in- cluded: (1) A fungicide spray program alternating between Bravo 720 (one pint per acre) and Ridomil/Bravo 81 (1.5 pounds per acre) weekly, beginning when plants were four inches tall and continuing until harvest; (2) A fungicide spray program alternating between Bravo 720 (one pint per acre) and Ridomil/Bravo 81 (1.5 pounds per acre) weekly, beginning at bloom and continuing until harvest; and (3) A fungicide spray program consisting of Bravo 720 (one pint per acre) applied weekly, EFFECT OF STARTING DATE OF A FUNGICIDE SPRAY PROGRAM ON TOTAL NUMBER OF FUNGICIDE SPRAYS APPLIED AT THREE ALABAMA FIELD SITES IN 1996 Begin spray program when: No. application at each site Fairhope Chilton Cullman Plants are four inches tall............. 6 6 6 Plants are at bloom............ 3 4 5 Disease first appears ..................... 3 0 1 Unsprayed control ............ 0 0 0 beginning when either early blight or late blight first appears (plots were scouted a minimum of twice per week) and continuing until harvest. Due to abnormally dry weather conditions in late spring during the experiment, there was little disease pressure at any of the sites. Trace amounts of early blight were observed at all three sites, but no late blight was noted. There were no differences in disease incidence among treat- ments. There were also few differences in yield among the treatments (data not shown). Fewer ap- plications were made when the spray program started at bloom and in the IPM scouting program. In either case, a cost savings would have been re- alized by the grower due to reduced fungicide ap- plications. It is still uncertain, however, how these alternative spray programs will perform when weather conditions favor higher levels of disease development. The dry conditions in 1996 were not favor- able for development of significant levels of late blight or early blight. Late blight can be very de- structive under cool, wet conditions and delaying fungicide applications under these conditions could be disastrous. Results from this study are preliminary and the experiments will be repeated in 1997. 12 ALABAMA AGRICULTURAL EXPERIMENT STATION 13 Transgenic Tomatoes Withstand CMV Epidemic JOHN MURPHY, ED SIKORA, AND KARRIE LOVINS Tomato plants genetically engineered to ex- press the cucumber mosaic virus (CMV) coat pro- tein gene were evaluated for the second year un- der the epidemic conditions in North Alabama. An epidemic caused primarily by CMV has dev- astated the fresh-market tomato industry in Blount and St. Clair counties each year since 1992. CMV has an extremely large natural host range and can be spread by at least 75 species of aphids in a nonpersistent manner. Due to the lack of resis- tant tomato varieties available to growers and because of the nature of CMV, the epidemic has continued unabated. As an alternative approach, nine genetically engineered tomato lines were evaluated under grower conditions for their abil- ity to withstand the extreme disease pressure that occurs in North Alabama. Plants were grown at a single location, in cooperation with a commercial grower. Plants were evaluated periodically for expression of CMV-like symptoms during the course of the growing season. Plants were tested for the pres- ence of the CMV antigen using indirect ELISA. Leaves from each plant were collected, stored on ice and transported to the laboratory. The first sign of viral symptoms occurred on the non-transgenic control (or susceptible con- trol) plants within three weeks of transplanting. During the course of the first three evaluation dates, obvious CMV-like symptoms were ob- served only on the non-transgenic control plants. In plants that became symptomatic at later times (by the fourth evaluation date), symptoms con- sisted primarily of upward curling of the leaves; however, those plants that developed symptoms at earlier times were usually more severely af- fected. This was particularly obvious for the non- transgenic control plants which became extremely stunted with deformed leaves (typical shoe-string- ing symptoms induced by CMV). Most plants, however, remained symptomless throughout the experiment. In contrast to evaluation of plants for symp- tom development, analysis of plants for CMV using ELISA indicated that most plants were in- fected. Among the nine varieties, percent infec- tion ranged from 60-100%. It should be noted, however, that the majority of plants accumulated low levels of CMV. Thus, even though most plants were infected with CMV, they appeared to resist high-level accumulation of the virus and as a result remained symptomless throughout the course of the experiment. In contrast, the non- transgenic control line accumulated high levels of CMV early after transplanting and developed severe symptoms. Data strongly suggest that genetically en- gineered tomato is able to resist the extreme pres- sures of the CMV epidemic in North Alabama. These plants resisted the expression of infection by CMV (i.e. viral symptoms) throughout much of the experiment (many never developed detect- able symptoms). Moreover, although a majority of the plants did become infected with CMV, the virus levels in these plants remained low. These results are in agreement with data obtained from 1995 trials of transgenic tomato plants. The use of genetically engineered tomato appears to be a valuable option to combat the CMV epidemic in North Alabama. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 14 Alabama's Fresh-market Tomato Growers Use Integrated Pest Management ELLEN BAUSKE, ED SIKORA, GEOFF ZEHNDER, AND JOE KEMBLE U.S. consumers are increasingly concerned with the use of pesticides in food production. As a result of public concern, the federal government mandated that by the year 2000, 75% of all crop- land should be farmed using Integrated Pest Man- agement (IPM) practices. In order to determine the level of IPM implementation in Alabama, fresh-market tomato growers in North Alabama (Blount County) and South Alabama (Geneva County) were surveyed. Results of the survey show that Alabama tomato farmers plant an average of 22 acres of tomatoes each year (see table). North Alabama producers applied slightly more insecticides and fungicides than producers in the South Alabama. A survey score of 0-50% was considered a low level of IPM usage, 51-75% a medium level, and 76-100% a high level. The average score on the survey was 57%. Clearly, Alabama's fresh-mar- ket tomato producers are well on their way to achieving the federal mandate. The survey was developed as part of the USDA/Land-Grant University IPM initiative by IPM teams from Alabama, North Florida, Geor- gia, Kentucky, North Carolina, South Carolina, and Tennessee. Teams were composed of grow- ers, private consultants, Extension personnel, and researchers. The survey listed IPM practices in three sections: cultural practices, pesticide appli- cation techniques, and specific pest management practices. In order to customize the surveys to the unique conditions in participating states, state team members weighted the IPM practices listed from 1 (low importance) to 4 (high importance). In Alabama, the team placed the most importance on IPM practices concerned with maintenance of pesticide application equipment, application prac- tices, insect and disease scouting, and control of viral diseases. Growers who used insect and dis- ease scouting, regularly maintained their spray equipment, and used cultural practices that re- duced the introduction and spread of disease tended to score high on the survey. Growers were also asked to identify insect, disease, and produc- tion problems, as well as any technology or re- search developments that they felt would benefit the industry. Producers in Geneva County identified early blight and fruitworm as their primary dis- ease and insect problems, while producers in North Alabama identified cucumber mosaic vi- rus, aphids, and stinkbugs as their primary pest problems. Growers in both areas identified dis- eases, insects, and poor weather conditions as their key production problems. The problems faced by Alabama's tomato producers were simi- lar to the problems faced by producers through- out the Southeast. In the process of creating this survey, the state IPM teams outlined a clear definition of IPM in fresh-market tomato production. These survey results establish a baseline which can be used to measure the success of programs designed to in- crease IPM adoption. The survey also provided an opportunity for growers throughout the region to identify pest problems of importance to them. Results of this survey can be used to influence the extension/research agenda in the universities in the Southeast. SUMMARY OF IPM SURVEY RESULTS Region No. growers Avg. production Avg. score Avg. no. applications Fungicide Insecticide Herbicide acres pct. South Alabama ........................... 10 17.8 61.2 7.9 8.6 2.1 North Alabama ........................... 15 25.4 55.2 10.0 10.1 1.9 ALABAMA AGRICULTURAL EXPERIMENT STATION Evaluation of Biological Control Treatments for Bacterial Spot Control on Tomatoes ELLEN BAUSKE, PAUL BACKMAN, JOE KEMBLE, AND ED SIKORA Field tests were designed to determine the effectiveness of two bacterial strains and chitin amendments in controlling early blight on tomatoes. However, Mother Nature had other designs; she provided a very stringent test of the ability of these biological control agents to limit the spread of bacterial spot disease. Unfortunately, the biocontrol agents were no match for bacterial spot. Two strains of the bacterium Bacillus thuringiensis (BP24A and BT8) were mixed and applied as foliar treatments. Commercial chitin preparations were also applied as foliar treatments on 'Marion' tomatoes. These bac- terial strains have previously demonstrated control of early blight. The chitins (CPT Insectinet 270 and 568, Chemical Products Technologies, Cartersville, Ga.) increase populations of chitinolytic (chitin degrading) microorganisms. Since chitin is a major component of many fun- gal cell walls, chitinolytic organisms can degrade fungal cell walls and have potential as biological control agents. Weekly treatments of these bio- logical controls were compared with weekly ap- plication of Bravo 90 DG (ISK Biotech, Mentor, Ohio). Bacterial spot spread quickly through all plots in the test. Leaves were sampled and rated for disease severity on a 0 (no disease) to 4 (se- vere disease) scale. There were no indications that EFFECT OF BIOLOGICAL CONTROL TREATMENTS ON SEVERITY OF BACTERIAL SPOT DISEASE OF TOMATO Treatment Disease rating' Untreated control ............................ ..... ....................... 1.99 Bacterial strains 2 ........ ................... .... .................. . . . . . 2.30 CPT Insectinet 270 .................................... ..................... 2.18 CPT Insectinet 568. .......................... 2.09 CPT Insectinet 270 and bacterial strains .......................... ........................... 2.68 CPT Insectinet 568 and bacterial strains .......................... ........................... 2.26 Bravo 90 DG .............................. .... ......................... 2.33 'Ten leaves were removed from each plant and bacterial spot sever- ity was determined using a 0 (no disease) to 4 (severe disease) scale. 2Two strains (BP24A and BT8) of Bacillus thuringiensis in a mix- ture. any of the treatments reduced disease severity in the presence of bacterial spot (see table). Yields were poor in all treatments due to damage from bacterial spot (data not shown). Ideally, biological control agents would be used to replace chemical pesticides. This test un- derscores some of the difficulties involved in the application of biological control agents. Neither the bacterial strains nor the chitins were effec- tive against bacterial spot. Use of copper com- pounds or antibiotics to control bacterial spot would have also reduced populations of benefi- cial bacteria, leaving the crop with no protection against early blight. Producers using these treat- ments may have to switch to chemical pesticides in the common event of a bacterial spot epidemic. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 15 Reproduction of Reniform Nematodes on Snap Beans Commonly Grown in Alabama ED SIKORA, ELLEN BAUSKE, JOE KEMBLE, AND LEONARD KUYKENDALL Reniform nematodes, which have been found in more than 25% of Alabama's counties, can cause serious damage to a variety of agro- nomic and horticultural crops. Results from an AAES study suggest that reproduction of reniform nematodes may vary on different snap bean cul- tivars commonly grown in the state. In the U.S., the reniform nematode is con- sidered the second most damaging nematode of cotton, causing yield losses of up to 70%. Fresh market beans, cowpeas, tomatoes, okra, and can- taloupe are also particularly susceptible to dam- age from the pest. Resistance to reniform nema- todes has been reported in some soybean culti- vars but had not been previously evaluated in snap beans. Ten commercially available snap bean cul- tivars (see table) were evaluated in a Chambers County field known to be infested with reniform nematodes. Seed were planted on April 29, 1996. Soil samples were taken at planting and on July 11 (approximate day of harvest) for nematode analysis. Extremely dry conditions during the growing season resulted in a poor stand and ex- tremely low yields. Reniforr nematode reproduction was great- est on 'Pod Squad,' with the population more than doubling during the growing season (see table). Populations also nearly doubled on 'Magnum.' Few differences were observed in reproduction of the nematode among 'Opus,' 'Blue Lake,' 'Rushmore,' 'Green Crop,' or 'Bronco.' The population appeared to only maintain itself at "at- planting" levels on 'Mustard' and 'Strike,' while populations decreased on 'Goldrush.' Results indicate that reniform nematode re- production can vary greatly among commercial snap bean cultivars. While some cultivars, such as 'Pod Squad' and 'Magnum,' appeared to cause an increase in nematode reproduction, others, such as 'Mustard,' 'Strike' and 'Goldrush,' ap- peared to only maintain or reduce nematode popu- lations. At this time, it is uncertain if this is due to cultivar tolerance or resistance, or simply due to environmental factors. How these differences in populations levels effect yield is also unknown. This study will be repeated in both greenhouse and field tests in 1997. REPRODUCTION OF RENIFORM NEMATODES ON 10 SNAP BEAN CULTIVARS IN CHAMBERS COUNTY, 1996 Cultivar No. reniform nematodes Population differential Population index 2 4/29 7/11 Mustard ......................................... 359 414 55 1.15 Pod Squad ..................................... 359 794 434 2.21 Opus ............................................. 333 509 176 1.52 BlueLake ..................................... 275 446 171 1.62 Rushmore ...................................... 362 522 160 1.44 Goldrush ....................................... 376 143 -239 0.38 Magnum ........................................ 648 1,259 611 1.94 Strike ............................................. 445 529 84 1.18 Green Crop ................................... 374 600 226 1.60 Bronco ........................................... 379 516 137 1.36 'Final nematode population minus population at time of planting. 2 Population at harvest divided by population at time of planting. 16 ALABAMA AGRICULTURAL EXPERIMENT STATION 1996 FRUIT AND VEGETABLE RESEARCH REPORT 17 Molecular Markers in Watermelon FENNY DANE, XIAN ZHANG, AND BILLY RHODES Information needed to grow and maintain plants is encoded in the structure of DNA as genes on chro- mosomes. This information is translated into proteins, including enzymes and hormones, that regulate plant growth and development. Plant improvement has al- ways relied on the evaluation and selection of the right combination of genes. A large number of genes is of- ten required to improve even the simplest of charac- teristics. The characterization of important genes and the determination of their chromosomal location has been difficult or often impossible. New DNA-based technologies allow researchers and plant breeders to track valuable genes in segregating populations using genetically linked molecular markers. Extensive sets of genetically mapped molecular markers have been produced for many species; however, little research has been conducted on watermelon, even though this crop is cultivated worldwide. Watermelon production in the Southeast is of- ten hindered by the susceptibility of available germplasm to several pathogens, especially Fusarium wilt and watermelon fruit blotch. Resistance mecha- nisms are invariably overcome by the pathogenic vari- ability of the pathogen. Alternative genes may be found in wild relatives, but combining many genes to provide broad sustainable resistance is often difficult. A recently developed strategy called bulked-segregate analysis allows the identification of DNA-based mark- ers linked to important disease resistance genes. Research was initiated at Auburn University to identify and target DNA-based markers linked to Fusarium wilt disease resistance. Segregating (F2) populations from a cross between a primitive water- melon (PI 296341), known for its resistance to Fusarium wilt, and 'New Hampshire Midget,' an early- maturing watermelon with small round fruit and sus- ceptibility to all races of the Fusarium wilt pathogen, were used. DNA was isolated from young seedlings. Seedlings were subsequently inoculated with the Fusarium wilt pathogen and evaluated for their resis- tance to different races of the pathogen. A high num- ber of polymorphic DNA markers were detected in the watermelon populations. At present, genetic analy- ses are being conducted. These mapped markers should enable us to dissect the control of complex traits such as disease resistance and provide plant breeders with information to manage these traits in a plant breeding program. Isozyme Markers in Kiwifruit FENNY DANE AND HONGWEN HUANG The availability of kiwifruit is an example of the successful development of a worldwide fruit in- dustry from a wild species. Related plants are found throughout Asia, but kiwifruit is native to the moun- tains and hills of South-Central and Southeast China. All species contain individual plants with either male or female flowers, but show variations in their basic chromosome number. This fact, and the small size and large number of chromosomes, greatly hinders the ge- netic study of traits important for the identification of cultivars and species in this genus. The majority of the breeding programs for cultivar improvement thus far have depended on extensive selections from natu- ral populations. In order to develop cultivars with higher quality, stress tolerance, and pest resistance, a knowledge of chromosome behavior and mode of in- heritance of traits is required. Protein electrophoresis, the migration of pro- teins or enzymes under the influence of an electric field, is among the most cost-effective methods of in- vestigating genetic phenomena at the molecular level. Isozymes, which are functionally similar forms of enzymes, have been used extensively in other fruit breeding programs as genetic markers for a variety of reasons. AAES research was conducted to establish isozyme markers for kiwifruit and to evaluate the varia- tion within and between different species. Hybridization studies were initiated at the ki- wifruit repository of the Wuhan Institute of Botany in Hubei, P.R. China. Progenies from interspecific crosses were used for genetic analyses. Isozyme as- says were conducted at Auburn University on winter dormant buds. Gels were assayed for many different enzymes and isozymes with high-resolution banding patterns were used. The isozyme data provided many useful markers. Even though the commercially devel- oped kiwifruit is known to contain six pairs of 29 chro- mosomes, it was found to behave genetically like a diploid (a plant with only two pairs of chromosomes). All cultivars of different commercial species can now be uniquely identified by any combination of three different isozymes. These results are important for the development of effective kiwifruit breeding strategies. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 17 Effect of Mulch Color on Strawberry Pro- duction using Annual Hill Plasticulture DAVID HIMELRICK AND RANDY AKRIDGE The effects of various types of plastic mulches on total, early, and late-season yield were evaluated for three years in an annual hill straw- berry production system at the Brewton Experi- ment Field in Escambia County. Seven mulch treatments were applied in the first two years with two additional mulches being evaluated in the third year. 'Chandler' plants typically averaged more than twice the yield of the day-neutral 'Selva' in all treatments. Since black plastic is the standard industry practice, treatments were compared against this benchmark. Based upon this compari- son, the black plastic mulch treatment differed only from the bare-ground treatment. Although not significantly different in any year, the top- performing mulch treatments varied with produc- tion year and cultivar. In the wet and warm harvest season of 1991, the highest-yielding treatments were IRT-76, clear, and ALOR-brown for 'Chandler'; and clear, black, and ALOR-brown for 'Selva.' In the dry and cool 1992 season, the top performers were white on black, black, and ALOR-brown for 'Chandler'; and ALOR-brown, IRT-76, and white on black for 'Selva.' For the cool and moderately wet 1993 season, the best performance was re- corded on black, white on black, and clear for 'Chandler'; and black, IRT-76, and clear for 'Selva.' The bare-ground treatment consistently produced the lowest yields. Inconsistent results were seen when using various plastics to influence soil temperature and affect the aerial microclimate around the plant to TOTAL YIELD FOR 'CHANDLER' STRAWBERRIES GROWN ON VARIOUS TYPES OF PLASTIC MULCHES Treatment 1991 1992 1993 Clear ................... 18,493 18,996 22,443 Black ..................... 16,698 21,844 23,398 Black/White ......... 17,570 20,220 21,314 White/Black ......... 15,052 23,337 23,166 IRT-76 ................... 19,080 20,379 20,489 ALOR-Brown ....... 17,974 20,961 20,822 Red .......................... -- -- 20,605 Silver .............. -- -- 22,081 Bare Ground. 12,644 18,579 13,598 shift, accelerate, delay, or extend the harvest sea- son. Generally, the plastic mulches that produced the highest soil temperatures caused plants to flower and fruit somewhat earlier. The laminated white on black mulch produced the coolest soil temperatures of any mulch treatment and im- proved late-season performance in the two cool harvest season years. Average soil temperatures from warmest to coolest were black, black on white, clear, IRT-76, ALOR-brown, red, silver, white on black, and bare-soil treatments. After three years of research examining the feasibility of using a variety of plastic mulches to maximize production and possibly extend the fruiting season, black plastic mulch remains the best for commercial plantings. In addition to pro- ductivity, the inconsistency of other mulches, cost, availability, and weed control factors all contribute to this conclusion. In certain cases, a co-extruded white on black mulch may provide an opportunity to extend the harvest season later into the spring in certain years. 18 ALABAMA AGRICULTURAL EXPERIMENT STATION 19 Frost Protection of Satsumas with Microsprinkler Irrigation MONTE NESBITT, RONNIE MCDANIEL, AND BILL DOZIER The satsuma is a hardy, mandarin-type citrus that bears heavy crops of high-quality fruit. Satsumas are grown along the Gulf Coast on Poncirus trifoliata rootstock, but can be killed by temperatures below 25 0 F (depending on seasonal hardening). The com- mon method of protecting satsumas from freeze is to "bank" the crown of the tree with soil, which saves the graft union, but sacrifices the canopy. Substantial production is then lost for 4-5 five years while the canopy regrows. Freezes in successive years are very detrimental to reestablishment of trees. Better meth- ods of freeze protection are needed to make satsuma production a sustainable industry in South Alabama. Microsprinklers have been used successfully in other regions to protect tropical and subtropical fruits from frost and freeze. As water emitted from these low-volume sprinklers freezes, energy is released in the form of heat. Continual application of water by microsprinklers during the period of freezing tempera- tures keeps irrigated tissues at 32 0 F. A test was initiated at the Gulf Coast Substa- tion in Fairhope to compare placement and flow rates of microsprinklers in 'Owari' satsumas for freeze pro- tection. Budded trees were planted in March 1990. Tree spacing was 15 feet x 25 feet. Seven treatments were applied including: (1) control with no protec- tion; (2) control with typical soil banking; (3) low- volume (11 gallons per hour [gph]) microsprinkler placed on ground under tree; (4) high-volume microsprinkler (24 gph) placed on ground under tree; (5) high-volume microsprinkler placed in canopy; (6) high-volume microsprinkler placed in canopy with low volume microsprinkler on ground; and (7) high-vol- ume microsprinkler placed in canopy with high-vol- ume microsprinkler on ground. No significantly dam- aging frost or freeze events occurred until 1996. On Feb. 2, 1996, an advective freeze occurred at the Gulf Coast Substation. No buds, blooms, or fruit were present. The lowest temperature measured was 15 0 F. Temperatures ranged from 15 0 F to 34 0 F for a period of 85 hours. Irrigation was activated when tem- peratures 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 rang- ing from 270 to 32OF over a four-day period. During this freeze, irrigation was applied at night, because daytime temperatures were well above freezing. FREEZE DAMAGE OF 'OWARI' SATSUMAS WITH AND WITHOUT MICROSPRINKLER PROTECTION Treatment Pct. foliage Pct. foliage No. broken Stem retention retention limbs dieback' 3/7/96 3/22/96 Control (no protection)..........11.8 2.0 0.00 1.10 Control (banked)................... 10.8 2.0 0.00 1.30 11 gph ground.............23.7 9.1 0.05 1.15 24 gph ground.............30.7 20.2 0.05 1.65 24 gph canopy ............. 46.2 29.4 0.35 1.75 24 gph canopy/ 11 gph ground...........46.0 30.0 0.80 1.96 24 gph canopy/ 24 gph ground........... 53.9 40.1 0.25 1.55 10 = no dieback; 1 = 1-5%; 2 = 6-10%; 3 = 11-25%; 4= >25%. Unprotected satsuma trees and trees with soil banking were almost completely defoliated by the February freeze. Placement of a single 24 gph microsprinkler in the central canopy, with a second 24 gph sprinkler placed under the canopy, preserved more foliage than other treatments. When only one microsprinkler was used per tree, better protection of foliage was obtained by placing it in the central canopy area. Ice accumulation caused some limb breakage in each microsprinkler treatment, but the average num- ber of major limbs broken per tree was low. Trees in all treatments, including controls, ini- tiated new leaves following the last freeze. Tempera- tures in the whole test plot may have been elevated by the large number of irrigated trees in the study, offer- ing a level of protection to the control treatments. Unprotected trees in another orchard on the substa- tion had a much higher loss of major limbs. Visual ratings were made on a 0-4 increasing scale to esti- mate the amount of freeze damage on small-diameter shoots. While all treatments had some dieback of small shoots, unprotected controls had less than some of the irrigated treatments. This might be explained by the fact that ice buildup in the central canopy prevents microsprinklers from continually applying water to the outer shoots. No fruit was produced on unprotected trees in 1996, while irrigated trees set a small number of fruit. Fruit will be harvested in 1996 to determine if any irrigation method gave better yields. 1996 FRUIT AND VEGETABLE RESEARCH REPORT New Peach Thinning Material Evaluated BOBBY BOOZER, BILL DOZIER, JR., AND JIM PITTS While thinning peaches was not a problem for most peach producers in 1996, most seasons it is. Most years, hand thinning fruit runs from 30-35% of the total variable costs associated with peach production. During June 1996, an AAES research project was initiated to evaluate the po- tential of a new product for peach fruit thinning. Release LC (Abbott Laboratories) is a gib- berellic acid which has been shown to inhibit fruit bud formation in peaches. The product is now labeled in California, and several researchers in the Southeast are evaluating the product for use. 'Harvester' peaches (third leaf) were sprayed on June 12 with 50 parts per million of Release LC. Treatments varied with the amount of spray water delivered per acre and the addi- tion of a surfactant. Additional treatments will include the use of ethephon during November to increase winter hardiness and delay bloom. While no data has been collected from the study at this point, visual assessments have been made and reduced bud formation appears to have occurred. A pre-winter and post-winter bud count will be made and followed up with bloom counts per inch of shoot length. Touch-up hand thinning of fruit will be per- formed in 1997 and comparisons made based on treatments. A second application of treatments will be made in June 1997, and yields will be evaluated as wcil as fruit quality. Preliminary data should be available by April 1997 to see how this product performs un- der the study conditions. Information at that time will be based only on bud data. This study is on- going and will be modified over the next several years in an attempt to reduce the cost per acre associated with fruit thinning. Maximizing Irrigation in Peach Production BOBBY BOOZER, BILL DOZIER, JR., BETH GUERTAL, AND JIM PITTs Peach irrigation in Central Alabama con- sists of thseuse of drip-type emitters, usually two one-gallon-per-hour emitters per tree. The wide- spread use of irrigation has often been limited to final swell during dry years. Maintaining suffi- cient soil moisture during this period of time can be difficult with drip emitters. The use of micro- spray devices for irrigation has not been evalu- ated in Alabama for peach production, nor has the use of irrigation systems to supply fertilizer to the trees. In 1996, a study was initiated by AAES at the Chilton Area Horticulture Substation to evalu- ate the use of drip irrigation and micro-spray ir- rigation for supplying fertilizer. A block of 'Har- vester' entering their third leaf was used. Many crops are now fertilized through irri- gation systems. This approach could optimize the use of the fertilizer by reducing losses from leach- ing, runoff, and weeds. The study will look at tree growth and yield based on treatment effects. Fertilization of peaches involves modified broadcast or spot fertilization to the surface. In extremely wet springs, many growers are uncer- tain of the amount of available fertilizer remain- ing for tree growth and fruit production. This study will determine the most cost-effective method. With fertigation, less fertilizer may be required for optimum growth and yield. Not unlike many of the commercial peach producers, no fruit was harvested during the 1996 season. Growth measureme ts and leaf tissue samples were taken. These will be analyzed and results included in future updates. Soil solution access tubes were installed to remove soil solution at a depth of 36 inches. Ni- trate concentration will be determined on these samples to examine the potential loss of fertil- izer nitrogen from the different treatments. This study will be on-going for several more years. 20 ALABAMA AGRICULTURAL EXPERIMENT STATION I Evaluation of Fungicides for Scab and Glomerella Control on Pecans ED SIKORA AND RONNIE MCDANIEL Pecan scab is the most limit- EVALUA' ing factor to pecan production in the CONTROL Southeast. To control the disease, growers must maintain a calendar spray program from bud break through mid-August. In 1996, Abound (4 o Super Tin 8 Abound, a new fungicide from Enable 2E(8 Zeneca, Inc., was evaluated for its Super Tin 8 Enable 2E (8 ability to control pecan scab. Abound (3. The test was conducted at the Enable 2E (8 Super Tin 8 Gulf Coast Substation in Fairhope on then Aboun mature 'Cape Fear' and 'Cheyenne' Abound alter with Enable trees. The first three sprays of each SuperTin 8 fungicide treatment were applied at Unsprayed c two-week intervals during the pre- 'The first fun pollination period (see table). Cover cides are (T = Trace a sprays were applied at three-week 3 Abound was intervals starting three weeks after the final Sup 4 Fungicidesv the final pre-pollination spray and and Abound were continued through mid-August. then Super T In one treatment, three applications Super Tin (7. three weeks of Abound were applied at two-week intervals after the final cover spray to determine if it would affect development of Glomerella, a late-season disease of pecan. Also evaluated was a fungicide program that alternated Abound with the commonly used fungicides, Su- per Tin 80WP and Enable 2E. Leaf scab ratings were taken on July 7 and nut scab ratings were taken on Sept. 5. No differ- ences were observed among fungicide treatments for either leaf or nut scab, though all treatments had less disease then the unsprayed control (see table). Dry weather during May and June resulted TION OF FUNGICIDE SPRAY PROGRAMS FOR PECAN SCAB 1, ON 'CHEYENNE' AND 'CAPE FEAR' TREES IN FAIRHOPE Pct. leaf scab 2 Pct. nut scab 'Cheyenne' 'Cape Fear' 'Cheyenne' 'Cape Fear' z.) then 0WP (7.5 oz.) ........... 4.4 T 52.1 2.0 oz.) then 30WP (7.5 oz.) ........... 5.3 T 54.7 3.0 oz.) then 0 oz.) ....................... 3.1 T 52.0 0.2 oz.) then T0WP (7.5 oz.) id (4 oz.) 3 .. . . ..... ........ 5.7 T 61.0 1.4 nating program r 2E and 0W P 4 .......................... 7.8 T 49.7 0.8 ontrol .................... 18.4 6.0 96.6 68.2 ngicide listed is a pre-pollination spray, while the subsequent fungi- ,er sprays. Rates are described in parentheses. mounts of leaf scab was observed. applied three times at two-week intervals beginning two weeks after er Tin cover spray. were applied in the following order: Abound (4 oz.), Enable (8 oz.), (4 oz.) were applied as pre-pollination sprays at two-week intervals; in (7.5 oz.), Abound (3 oz.), Super Tin (7.5 oz.), Abound (3 oz.), and .5 oz.) were allied as cover sprays at three-week intervals beginning after the last pre-pollination spray. in unusually low levels of leaf scab. More dis- ease was observed on 'Cheyenne' trees than on 'Cape Fear,' as expected, since 'Cheyenne' is considered more susceptible to scab. Glomerella was not observed during the test, so no conclu- sions could be made on the ability of Abound to control this disease. Based on the results of this test, it appears that a fungicide spray program that included Abound in the pre-pollination or cover spray period would be a viable treatment for pe- can scab control in Alabama. 1996 FRUIT AND VEGETABLE RESEARCH REPORT 21 Evaluation of Fungicides for Pecan Scab Control in Central Alabama ED SIKORA AND JIM SMITH Pecan scab is the most limiting factor to pecan production in the Southeast. In 1996, a fun- gicide trial was conducted to evaluate fungicides that are not currently labeled for use on pecans for their ability to control scab. The fungicides, Bravo 720 and IB11522 (ISK Biosciences), and Folicur 3.6F (Bayer Corp.), were evaluated with commercially avail- able compounds and against standard spray pro- grams (full-season Super Tin 80WP and Orbit 3.6EC pre-pollination sprays with Super Tin 80WP cover sprays). Results indicate that Bravo 720, IB 11522, and Folicur 3.6F performed as well as the standard fungicides currently used in Ala- bama. The test was conducted at the Turnipseed- Ikenberry Place in Union Springs on mature 'Stuart' trees. The first three sprays of each fun- gicide treatment were applied at two-week inter- vals during the pre-pollination period. Cover sprays were applied at three-week intervals start- ing three weeks after the final pre-pollination spray and continuing through mid-August. Trees were evaluated for leaf scab incidence on June 6 and for nut scab on Sept. 5. Dry weather during May and June resulted in unusually low levels of leaf scab. No differences in leaf scab were observed among treatments, including the unsprayed control. No differences were observed among fungicide treatments for nut scab, although all treatments had less disease incidence than the EVALUATION OF FUNGICIDES FOR PECAN SCAB CONTROL ON STUART TREES IN UNION SPRINGS, 1996 Treatment' Rate Pct. nut scab IB 11522 (pre-pollination) 2.0 pt. then Super Tin 80 WP (cover) 7.5 oz................... 8.2 Bravo 720 (pre-pollination) 2 1.0 pt. plus Enable 2E (cover) 4.0 oz .................. 5.2 Super Tin 80WP (full season) 3 7.5 oz ........................ 14.4 Folicur 3.6F (pre-pollination) 4.0 oz. then Super Tin 80WP (cover) 7.5 oz .................. 1.9 Folicur 3.6F (pre-pollination) 6.0 oz. then Super Tin 80WP (cover) 7.5 oz .................. 1.4 Orbit 3.6EC (pre-pollination) 4.0 oz. then Super Tin 80WP (cover) 7.5 oz................... 6.9 Unsprayed control --....................... 33.9 'Pre-pollination sprays were applied three times at two-week in- tervals and were followed by five cover sprays applied at 21-day intervals through mid-August. 2 Bravo 720 and Enable were applied as a full season tank-mix. 3 Super Tin was applied alone, full season. unsprayed control (see table). All fungicides tested appeared to control pecan nut scab. Fur- ther evaluation of Bravo 720, IB11522, and Folicur 3.6F are needed to determine the efficacy of these compounds for leaf scab and under weather conditions more favorable for the devel- opment of pecan scab. 22 ALABAMA AGRICULTURAL EXPERIMENT STATION 1996 FRUIT AND VEGETABLE RESEARCH REPORT 23 Evaluation of New Pecan Cultivars for Scab Resistance BILL GOFF, MONTE NESBITT, AND LYNN SLOCUM Pecan Scab is extremely difficult and ex- pensive to control. Susceptible cultivars must be sprayed 6-10 times each growing season in Ala- bama to prevent major foliage and nut loss. The airblast sprayers that are needed to apply protec- tive fungicides to mature pecan trees are cost-pro- hibitive to small farms or home settings. A pri- mary goal of AAES researchers is to identify new pecan cultivars that have strong genetic resistance to pecan scab, and will be productive without a great dependency of fungicides. In 1995, an evaluation of scab resistance was initiated at the E.V. Smith Research Center in a high-density planting. Test cultivars included 97 unreleased selections from the USDA Pecan Breeding Program PECA in Texas (example: 72-6-12); two Cultivar named USDA cultivars (Houma and Oconee); two popular culti- 70-3-34 ................. vars originating in Alabama Mount................... 86-4-151 .............. (Surprize and Jubilee); six com- 89-11-3............... monly planted cultivars (Curtis, Dixie ..................... Elliott, Desirable, Farley, Deakle p.......... Melrose, and Moreland); and 40 4X ......................... new or unknown seedling culti- 87-10-42 ............. McMillan ............. vars, reported to be scab resis- Elliott-AL ............ tant. Five trees of each test culti- 82-15-9................. Farley ................... var were propagated by bark Forey .................... grafting in April 1995. Failed Schutz 1............... Schutz 2 ............... grafts were re-grafted in April 87-2-631 .............. 1996. 86-4-178 .............. 89-10-7 ................. Leaflets were rated for scab Buchel 1 ............... on a 1-5 scale, where 1 = no in- Carter.................... fection; 2 = trace to 10%; 3 = 11- HghJenkins 1 .............. 25%; 4 = 26-50%; and 5 = 51- Elliott-TX ............ Syrup Mill ........... 100% infection. Ratings were Tinker................. made in July 1995, and August 81-6-86................. 1996. Scab was also measured in 87-12-107 ............ 1995 on stem tissue, by counting Curtis.................... the number of scab lesions igh88-1-71 ................. present on the worst 12-inch stem section. Necrotic spots caused by black aphid feeding were counted on each culti- var in 1995 and 1996. Cultivars were eliminated from study if a single tree had a leaf scab rating higher than 2, or if stem scab lesions exceeded 10 on a 12-inch stem section. More than 75% of the 147 selections had moderate to severe levels of scab that would pre- clude their culture in Alabama without fungicides. Seven cultivars exhibited no leaf scab through two seasons and had very low numbers of scab lesions on stems. Because the pecan scab fungus has the ability to evolve rapidly, future observations must be made to ascertain the long term stability of resistance in these cultivars. N CULTIVARS WITH GOOD RESISTANCE TO SCAB 1996 mean 1995 mean Mean stem 1995 black 1996 black leaf scab leaf scab lesions aphid damage aphid damage ...... 1.0 1.0 0.5 6.0 37.0 ...... 1.0 1.0 1.0 7.5 14.5 ...... 1.0 1.0 1.3 9.0 11.3 ...... 1.0 1.0 2.0 3.3 44.7 ...... 1.0 1.0 3.0 2.3 43.5 ...... 1.0 1.0 4.5 5.0 33.8 ...... 1.0 1.0 5.0 0.0 14.0 ...... 1.0 -- 1.5 5.0 35.0 ...... 1.0 1.5 0.5 22.5 21.0 ...... 1.0 1.5 5.5 1.8 13.8 ...... 1.2 1.0 6.0 1.5 49.4 ...... 1.3 1.0 1.5 1.5 22.3 ...... 1.3 1.0 1.5 1.5 22.3 ...... 1.3 1.0 4.0 7.0 29.5 ...... 1.3 1.0 5.0 2.3 19.5 ...... 1.3 1.0 5.3 0.5 16.0 ...... 1.3 1.3 0.5 6.0 18.8 ...... 1.3 1.3 1.0 2.5 18.3 ...... 1.3 1.3 2.7 5.7 14.0 ...... 1.3 1.0 7.0 0.0 14.5 ...... 1.3 1.3 1.7 6.7 40.3 ...... 1.3 1.3 1.7 8.8 23.8 ...... 1.5 1.0 4.3 0.3 22.7 ...... 1.5 1.0 5.6 1.7 22.3 ...... 1.5 1.3 4.0 0.0 16.5 ....... 1.5 1.3 4.3 1.0 12.3 ...... 1.5 1.3 1.0 6.3 46.0 ....... 1.5 2.0 1.3 8.7 14.0 ....... 1.7 1.0 3.3 4.5 26.5 ....... 1.7 1.0 7.0 0.0 17.0 ....... 2.0 1.5 -- 11.0 38.7 ....... 2.0 2.0 4.0 5.0 12.0 1996 FRUIT AND VEGETABLE RESEARCH REPORT 23 Yield and Kernel Percentage of 22 Pecan Cultivars from 1992-1995 MONTE NESBITT, BILL GOFF, LYNN SLOCUM, AND RONNIE MCDANIEL The pecan industry in Alabama suffered four disastrous years from 1992 to 1995. Following Fhvavy crops and severe disease pressure in 1991, total state production in 1992 was 4 million pounds, a low not seen since 1940. In 1993, state produc- tion was 27 million pounds, the highest level since 1981. Overproduction in 1993 caused nut quality to be poor, and severely depressed prices paid to growers. Trees were stressed from overbearing and set very little crop in 1994. Total state production in 1994 was 4 million pounds, and nut quality was poor. Hurricanes in August and October, 1995 de- stroyed trees, decimating an estimated two-thirds of the crop, and severely reducing nut quality. A pecan orchard was planted at the Gulf Coast Substation in Fairhope in 1983 to compare perfor- mance of several cultivars. Trees were planted at 40 x 40 feet, and were established with drip irriga- tion. Weeds were controlled by herbicide applica- tions, maintaining a sod and strip orchard floor. Soil and leaf samples were taken annually, and fertiliz- ers were applied accordingly. Fungicide applica- tions were begun at bud break, and a full-season schedule was maintained. Insects were controlled when scouting indicated an economic injury level was Cultivar present. Yield and nut quality param- eters (nut size, kernel percentage, and ker- Jubilee........ nel grade) were measured each year. In Pioneer ....... 1992, the trees were in their 10th leaf. Forkert ....... Nut production and kernel per- Harris Super centage measurements in this trial from Sumner ....... Creek .......... 1992-1994 reflect the general produc- Desirable.... tion problems encountered statewide Kiowa ......... during the same time. Data from these rCandy..... years, however, is useful in identify- Stuart .......... ing cultivars that perform well in South Pawnee ....... Melrose ...... Alabama under adverse conditions. Davis .......... Kernel percentage, in particular, is an Choctaw ..... important indicator of cultivar perfor- Cape Fear.... mance. 'Forkert,' a cultivar known for Maramec .... producing high-quality kernels, had the Jackson....... Shoshoni .... best kernel quality in this study from Cheyenne ... 1992-1995. Average percent kernel for 'Pounds of ii all cultivars was low, but 'Shoshoni,' 2 Calculated I 'Gloria Grande,' 'Cheyenne,' and 'Davis,' had es- pecially low kernel percentages. The benchmark for pecan yields in the South- east is 1,000 pounds per acre per year. Over the four-year period presented, only three cultivars pro- duced at this level. The best cultivar of these three was 'Surprize,' which had better kernel quality and a more consistent pattern of annual production as an older tree. 'Cape Fear' and 'Elliott,' popular cultivars in Alabama, were among the lowest-yield- ing cultivars over the four-year period. 'Elliott' is susceptible to late summer defoliation by insects and mites, which reduced yield in 1995. 'Cape Fear' is a heavy-bearing cultivar, but in 1993, kernel qual- ity was so poor that nuts were unmarketable. When yield and kernel percentage are con- sidered, 'Pioneer,' 'Surprize,' 'Forkert,' 'Harris Super,' 'Creek,' and 'Kiowa' had the best perfor- mance from 1992-1995. Some of these cultivars have other limitations not discussed here, includ- ing dark kernel color, kernel specks, weak shell sutures, late nut maturation, etc. KERNEL PERCENTAGE AND MARKETABLE YIELD 1 Avg. Yield Yield Yield Yield Avg. yield/ pet. kernel 1992 1993 1994 1995 acre/year' ................44 48 103 0 58 1,421 ................46 20 88 0 74 1,240 .................47 31 88 0 62 1,231 .................56 14 76 0 42 894 ..............48 0 69 0 55 844 ................ 50 27 52 2 38 809 ................ 47 13 65 0 39 792 ................44 43 55 1 16 779 ................48 48 34 1 26 743 .................37 16 47 11 28 692 ................41 2 57 0 39 664 ................41 16 61 0 19 660 ................52 15 49 0 30 643 ................49 33 44 0 4 558 ................33 5 54 0 21 547 ................47 12 44 0 17 499 ................49 8 48 0 16 490 ................ 43 4 0 0 62 455 ................52 13 36 0 14 430 ................ 50 9 20 1 15 303 ................ 31 0 0 0 28 189 ................40 4 6 0 5 100 n-shell nuts per tree. based on 40 x 40-foot spacing, which equals 27.2 trees per acre. 24 ALABAMA AGRICULTURAL EXPERIMENT STATION Weed Control Increases Yield and Economic Return from Young 'Desirable' Pecan Trees WHEELER FOSHEE, BOB GOODMAN, MIKE PATTERSON, AND BILL GOFF The economic benefits of improved weed control in pecan orchards have not been fully es- tablished. Yields and corresponding economic returns above treatment costs were determined from young 'Desirable' pecan trees grown for nine seasons under 10 combinations of orchard floor management practices and irrigation at the Gulf Coast Substation in Fairhope. Orchard floor management practices in- cluded (1) weedy-unmowed, (2) weedy-mowed, (3) total weed control with herbicides, (4) grass control only with herbicides, and (5) weed con- trol by disking. Herbicide applications included oryzalin (Surflan AS) plus paraquat (Gramoxone) in March, followed by glyphosphate (Roundup) in June and August, and an application of norflurazon (Solicam) in the fall. Also, in the sec- ond growing season, simazine (Princep) was added to the oryzalin-paraquat treatment. Mowing and disking were performed on a two-week and four-week schedule, respectively. Pecan samples and grading information were pre- sented to a commercial buyer who established a price he would offer for the pecans if buying in TABLE 2. FINANCIAL SUMMARY: CUMULATIVE DEBT PER ACRE 1 Year None Mowing Total Grass Disking herbicide herbicide Irrigated 1989.... $1,920 $1,936 $1,970 $1,934 $1,933 1990...... 2,284 2,316 2,184 2,312 2,091 1991...... 2,663 2,712 2,175 2,572 2,000 1992...... 2,473 2,520 389 2,255 630 1993...... 2,182 2,276 -528 1,972 -198 1994...... 2,554 2,584 -281 2,331 10 Non-Irrigated 1989.... $1,847 $1,863 $1,897 $1,861 $1,860 1990...... 2,208 2,240 2,065 2,137 2,234 1991...... 2,584 2,633 2,188 2,524 2,459 1992...... 2,609 2,246 535 2,369 1,902 1993...... 2,553 1,870 -540 2,044 1,534 1994...... 2,914 2,215 -293 2,439 1,839 'Negative numbers indicate a positive net present value. TABLE 1. CUMULATIVE YIELDS OF IRRIGATED ANDNON-IRRIGATED PECAN ORCHARDS No weed control .......... 1,228 1,055 1,142 M owing ......................... 1,614 1,472 1,544 Total control with herbicides .......... 4,292 3,930 4,127 Grass control with herbicides..........1,802 1,773 1,789 Disking..... ............ 3,626 2,255 2,947 Average ...................... 2,512 2,097 wholesale commercial lots on the date pecans could have been delivered to market. Treatment costs were based on vendor surveys and Alabama Cooperative Extension Service budgets. In the humid environment of South Ala- bama, the effect of irrigation on yield and crop value was negligible (Table 1). Total weed con- trol with herbicides, however, increased cumula- tive yield through the ninth season by 361%, com- pared to no weed control. By the eighth season, this floor management technique had recovered establishment costs for the young 'Desirable' trees (Table 2). 1996 FRUIT AND VEGETABLE RESEARCH REPORT 25