F nit 6 Vegetable e cz C w 8- P __:'~"' " lp"B-" S"'~ ste N n: /$~ ~-r ~"rrr rrrrr- 4 ~ "~~!t 2 ~ s ~'a h t : ? ' * ~ ' " #. ' a j t ~? I. I "~c~e 4ft4) ~" : ~a -, .V i: .i4-:;-*, ' 4 ~ _ ~ ~ ~ ' .-:-i---l-ii-i:::~:: *::: : k4-: I;-.-:::::::g:;, -. ' ; A - Research Report Series No. 11 April 1996 Alabama Agricultural Experiment Station Lowell T. Probish, Director Auburn University, Alabama L V T" ru: I CONTENTS Authors....................................................................................................................1. Influence of Mulch and Fumigation on Production of 'Sunny' Tomatoes............................................................................. 2 Ev aluation of Transgenic Tomatoes in North Alabanma.................................................................................................... 3 Evaluation of NS-83 for Control of Cucumber Mosaic Virus of Tomatoes ....................................................................... 4 Evaluation of Fungicides Using Fixed and Weather-timed Spray Programs for Blight Control in Tomatoes...........................................................5 Ev aluation of TOM-CAST for Early Blight Control on Tomatoes .......................................................................... 6 Double-cropping on Black Polyethylene Mulch: Fall Collards Follow~ing Spring Tomatoes...................................................................... 7 Double-cropping on Black Polyethylene Mulch: Trellised Cucumbers Follow~ing Tomatoes ..................................................................... 8 Optimal Timing of Insecticides for Control of Picklew.orn on Cucumber and Squash....................................................................... 9 Root-Colonizing Bacteria for Control of Bacterial Wilt Disease and the Cucumber Beetle Vector ..................................................................... 10 Reflective Mulches Aid in Control of Aphid-Borne Viruses in Summer Squash......................................................................................... 12 Potential New Watermelon and Cantaloupe Varieties ...................................................... 13 Double-cropping on Black Polyethylene Mulch: Fall Broccoli Following Spring Bell Peppers................................................................. 14 Lipid-Based Edible Coatings Improved Shelf Life and Consumer Acceptance of White Bell Peppers ......................................................... 15 Chitosan Coating Delays Postharvest Ripening of Bell Pcppers......................................... 16 Response of Bell Pepper Yields to an Irrigation Scheduling Model .................................... 17 Subjective and Objective Evaluation of Color in Bell Peppers........................................... 18 Two New Pinkeye Southernpeas Released....................................................................... 20 The Value Of Host Plant Resistance in Controlling Cowpea Curculio in Southernpeas ......................................................... 21 Is Silver Queen Still the Best-Tasting Sweet Corn? 9 ................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Effect of Rate of Banded and Broadcast Phosphorous on Yield of Sweet Corn.............................................................................................. 23 Ev.aluation of Foliar-applied Insecticides for Control of Whitefringed Beetle in Sweetpotatoes...................................................................... 24 Biocontrol Of Black Rot of Cabbage with Plant Growth Promoting Bacteria: Detection Through Bioluminescence.............................................. 25 Evaluation of Fungicide Spray Programs for Brown Rot Control on Peaches ............................................................................ 26 Evaluation of Fungicides for Brown Rot and Scab Control on Peaches...................................................................................... 27 Evaluation of Mechanical Thinners on Bloom/Fruit Removal and Yield of Encore Peaches ......................................................................... 28 Information contained herein is available to all without regard to race, color, sex, or national origin, First printing 3M, April 1996. Rabah Aynaou Graduate Research Assistant AU Horticulture Ellen Bauske Extension Associate AU Horticulture Bobby Boozer Area Horticulturist Chilton Area Horticulture Substation George Boyhan Senior Research Associate AU Horticulture Teri Briggs Research Technician AU Entomology James Brown Associate Professor AU Horticulture Arnold Caylor Interim Superintendent North Alabama Horticulture Substation Oyette Chambliss Professor Emeritus AU Horticulture Irma Chang Research Associate AU Cell Science Center Cindy Channell-Butcher Research Technician AU Horticulture Fenny Dane Assistant Professor AU Horticulture Bill Dozier Department Head AU Horticulture Vannessa Drouot Visiting Scholar AU Horticulture John Eason Superintendent (Retired) Sand Mountain Substation Ronald Eitenmiller Professor Food Science and Technology University of Georgia Gary Gray Assistant County Agent Chilton County Nancy Green Department Head AU Nutrition and Food Science AUTHORS Elizabeth Guertal Assistant Professor AU Agronomy and Soils Robert Hagenmaier Research Chemist USDA South Atlantic Area Citrus & Subtropical Products Laboratory Dave Himelrick Professor AU Horticulture Marlin Hollingsworth Superintendent (Retired) North Alabama Horticulture Substation Gene Hunter Senior Research Associate AU Horticulture Joe Kemble Assistant Professor / Co-editor AU Horticulture Joe Kloepper Department Head AU Plant Pathology Tracey Land Research Technician AU Horticulture Joe Little Superintendent Lower Coastal Plain Substation Karrie Lovins Research Associate Plant Pathology Christy Moore Visiting Student Howard Hughes Future Life Science Scholar Program Tim Motis Graduate Research Assistant AU Horticulture John Murphy Assistant Professor AU Plant Pathology Joe Norton Professor Emeritus AU Horticulture John Owen Superintendent Piedmont Substation Jim Pitts Superintendent Chilton Area Horticulture Substation Marvin Ruf Interim Superintendent Sand Mountain Substation Laura Sanders Computer Specialist Research Data Analysis Joe Shaw Associate Professor AU Botany and Microbiology Richard Shelby Research Associate AU Plant Pathology Ed Sikora Associate Professor AU Plant Pathology Amy Simonne Postdoctoral Fellow AU Nutrition and Food Science Eric Simonne Postdoctoral Fellow AU Horticulture Benjaporn Tangsukkasemsan Graduate Research Assistant AU Horticulture Sadik Tuzun Associate Professor AU Plant Pathology Ted Tyson Associate Professor AU Agricultural Engineering Gang Wei Postdoctoral Fellow AU Horticulture Larry Wells Interim Superintendent Wiregrass Substation Jimmy Witt Superintendent E.V. Smith Research Center Horticulture Unit Floyd Woods Associate Professor AU Horticulture Changbin Yao Graduate Research Assistant AU Entomology Geoff Zehnder Associate Professor AU Entomology For more information, call Robyn Hearn at the AAES Office of Research Information, (334) 844-4877. 2 ALABAMA AGRICULTURAL EXPERIMENT STATION Influence of Mulch and Fumigation on Production of 'Sunny' Tomatoes JAMES BROWN, TIM MoTIs, TED TYSON, JIMMY WITT, CINDY CHANNELL-BUTCHER, LAURA SANDERS, AND ED SIKORA Polyethylene mulch is commonly used E in vegetable production to control weeds, conserve moisture and fertilizer levels, and to modify soil temperature, with resulting improvement in plant growth and devel- opment. An undesirable consequence of wi using conventional black plastic mulch is Bu that it does not decompose and must be re- wi moved following harvest. Bu However, AAES research showed that wi a new mulch material known as Styrofan Ba BN 1248 provides many of the same ben- Ba efits as black plastic when used on tomato wi plants, but it can be plowed into the soil Ba after harvest. Styrofan, a biodegradable wi polymer produced by BASF Corp., is Ba sprayed on soil and dries to a film. wi In field plots at the E.V Smith Re- Ba wi search Center in Shorter, irrigation tubing Ba was laid in the center of 13.9-inch-high, wi 35.8-inch-wide, single-row pressed beds. Ba Rows were spaced 59 inches from center wi to center. Mulch treatments included 1.25- Ba mil black plastic, blue-black Styrofan wi sprayed over beds at a rate of 105.5 gal- Ba lons per acre. In addition, four fumigant 2 treatments were tested: Busan 1020 at 103 - gallons per acre and Basamid at 300, 375, and 450 pounds per acre. These were compared to control plots where the herbicide Treflan was used without mulch. Busan 1020 was injected through the drip system to the plant beds. Basamid treatments were broadcast and incor- porated into the upper surface of the soil beds. Treatments were applied and tomato plants were transplanted to the field in May. With few exceptions, the total marketable tomato yield among treatments was similar (see table). Regardless of fumigants, weeds were FFECTS OF FUMIGANTS AND MULCH ON TOTAL MARKET- ABLE TOMATO YIELD AVERAGED OVER ALL DATES eatment Total number Total weight no./a. tons/a. isan 1020 - 103 gal./a. th no mulch ......... ............... 21,360 4.64 isan 1020 -103 gal./a. th Styrofan ........... .............. 22,860 4.83 isan 1020 -103 gal./a. th plastic mulch ................. 25,420 5.53 isamid - 300 lb./a. th no mulch .................. ...... 19,310 4.29 asamid - 300 lb./a. th Styrofan ......................... 24,660 5.83 isamid - 300 lb./a. th plastic mulch ...... ........... 22,160 5.21 isamid - 375 lb./a. th no mulch ......... ............... 23,800 5.62 isamid - 375 lb./a. th Styrofan ......................... 20,230 4.71 asamid - 375 lb./a. th plastic mulch ...... ........... 16,860 3.48 samid - 450 lb./a. th no mulch ............................... 20,310 4.89 samid - 450 lb./a. th Styrofan ................................ 18,350 4.67 samid - 450 lb./a. th plastic mulch ........................ 24,530 5.82 eflan control.............................. 20,840 5.38 100% controlled on plots where black plastic mulch was used. On the control plots, percent weed population ranged from 1.5% on May 23 to 16% on June 22. This one-year study showed that the lowest rate of Basamid will produce tomato yields equal to the higher Basamid test rates with either mulch. Therefore, 300 gal- lons per acre of Basamid is the suggested ap- plication rate. Mulch selection would depend on site location and/or climatic conditions. FRUIT AND VEGETABLE RESEARCH REPORT 3 Evaluation of Transgenic Tomatoes in North Alabama JOHN MURPHY, ED SIKORA, AND KARRIE LOVINS Since 1992, viral diseases have devastated fresh market tomato production in some North Alabama counties. AAES studies identified five viruses in the area, but cucumber mosaic cucumovirus (CMV) is clearly the predominant pathogen. Unfortunately, there are no commer- cially acceptable tomato varieties able to resist CMV infection. And using insecticides to con- trol aphids, which transmit CMV, is ineffective because only very brief insect contact is needed to spread the virus. An AAES study in Blount County examined the use of genetically engineered, or transgenic, tomato plants with resistance to CMV. Such plants are created when a portion of viral ge- netic material is introduced into a single plant cell, and that cell is cultured into a fully devel- oped plant. Every cell in the "regenerated" plant then has that portion of the viral genetic mate- rial, thus inhibiting subsequent infection by the virus. Transgenic plants in this study expressed the CMV coat protein gene. The CMV transgenic lines provided extremely good pro- tection against CMV under conditions of high disease pressure. Transgenic tomatoes consisted of three lines, one transformed with the coat protein gene of a CMV subgroup II isolate (designated CP-II), and two lines transformed with the coat protein gene from CMV subgroup I and II iso- lates (designated CP1-I+II, and CP2-I+II). These lines were compared to a susceptible con- trol line, (-)CP, which was the same genotype as the transformed lines but did not contain CMV genetic material. 7.... Plants were evaluated for CMV symptom development three times during the growing season. All three transgenic lines held up ex- tremely well throughout the season. No CMV- like symptoms were observed in any of the transgenic lines at the first two evaluations. At the third, late-season rating period, four of 43 CP-II plants showed signs of CMV, but the two CP-I+II transgenic lines were still symptom- free. Seven of 48 control plants developed symptoms within one month of transplanting; by the third rating period, 46 of the plants were symptomatic. Plant samples were also analyzed by en- zyme-linked immunosorbent assay (ELISA), yielding results that complemented the visual observations. A mid-season ELISA evaluation showed that almost all transgenic plants were free of CMV, but 100% of the susceptible con- trol plants were highly infected with the virus. A late-season analysis revealed that transgenic tomato plants did become infected with CMV, but these plants prevented the virus from accu- mulating to the high levels seen in control plants. These data indicate that transgenic plants resisted accumulation of CMV until later in the season, and the virus did accumulate in the transgenic plants to detectable, but low levels by the end of the season. Thus, it appears as though the transgenic plants provide a level of defense against infection, upon becoming in- fected resist accumulation of the virus, and as a result prevent or reduce the development of symptoms and losses in yield. 4 ALABAMA AGRICULTURAL EXPERIMENT STATION Evaluation of NS-83 for Control of Cucumber Mosaic Virus of Tomatoes ED SIKORA, JOHN MURPHY, MARLIN HOLUNGSWORTH, AND ARNOLD CAYLOR Since 1992, a series of virus epidemics has reduced Alabama tomato production by an es- timated 20-25% per year. In a 1995 AAES study, a promising new biological control proved to be of little help in controlling this problem. The experimental product, NS-83, was de- veloped by researchers in China and is an or- ganic product made from decomposed plant material. NS-83 reportedly controls a broad spectrum of viral diseases on a variety of veg- etables. The test material, which is applied as a spray before and shortly after transplanting, induces a tolerance to mosaic-type viruses among treated plants. Cucumber mosaic virus (CMV), an aphid- transmitted virus, appears to be responsible for the majority of Alabama's tomato damage. The virus was found in 90% of fields surveyed and in more than 70% of plants tested in 1992. Con- ventional methods for managing CMV include weed control, the use of reflective mulches, application of crop oils, use of barrier crops, and altering planting dates and sites to avoid periods and locations where aphid populations are high. Under high virus pressure, as has been experienced in North Alabama recently, these practices can be ineffective. On-farm evaluations of NS-83 were estab- lished in Blount and St. Clair counties, and a third test was conducted at the North Alabama Horticulture Substation in Cullman. A process- ing tomato, "Hybrid 882," was grown in a greenhouse for four weeks, then transplanted to the field on June 21 in Cullman and June 22 in Blount and St. Clair counties. Treatments consisted of NS-83 applied: (1) on June 16 (six days before transplanting) and June 26 (four days after transplanting); (2) on June 16 and 26 and July 13 (18 days after trans- EVALUATION OF NS-83 FOR CONTROL OF CUCUMBER MOSAIC VIRUS OF TOMATO Treatment' Stand Plants with count CMV symptoms 7/20 7/27 8/10 pct. pct. pct. 1 ........................... 48 27.0 66.6 83.3 2 ....................... 53 52.8 67.9 98.1 3 ........................ 54 40.7 70.3 94.4 Control ................. 52 48.0 65.3 94.2 'Treatments are described in the text. planting); or (3) on June 16 and 26 and July 13 and 25 (25 days after transplanting). These treat- ments were compared to control plots. Each treatment consisted of a one row plot, 15 feet long, on 30-inch-wide and four-inch- high pressed beds. Tomatoes were grown on white plastic mulch at the Cullman and Blount county locations and on silver or black plastic mulch at the St. Clair county site. Fungicides were applied according to recommendations. Plants were observed weekly for the develop- ment of symptoms typical of CMV. Laboratory analysis of leaf tissue was conducted at the end of the experiment to substantiate field observa- tions. There was very low incidence of CMV at both the St. Clair and Cullman county locations. However, high CMV pressure occurred at the Blount County site throughout the season. Rela- tively high aphid populations were noted in the field only a few days after the tomatoes were transplanted. Symptoms of CMV were observed within a month after transplanting, and the pres- ence of the virus was confirmed by laboratory examination. Incidence of CMV was extremely high (83-98%) six weeks after transplanting. There did not appear to be any beneficial effect of NS-83 for the control of CMV in this experi- ment. FRUIT AND VEGETABLE RESEARCH REPORT 5 Evaluation of Fungicides Using Fixed and Weather-timed Spray Programs for Blight Control in Tomatoes ED SIKORA, ELLEN BAUSKE, AND MARLIN HOLLINGSWORTH An AAES experiment was conducted to evaluate fungicides for control offTmgal foliar diseases of tomato. Treatments included prod- ucts currently labeled for tomato (Bravo 720, Manzate 200DF, and Bravo C/M), as well as the experimental compounds Bravo 825 and Dacobre 27/27DG. These products were applied following the standard fixed, seven-day spray schedule. A weather-timed fungicide spray program known as TOM-CAST (Tomato Disease Forecaster) was also included in the test using Manzate 200DF. TOM-CAST uses two weather measure- ments, leaf wetness and air temperature, to as- sess disease risk and determine optimum fungi- cide spray intervals. The experiment was conducted at the North Alabama Horticulture Substation in Cullman in 1994. Tomatoes were transplanted on May 12. Each of seven treatments consisted of one-row plots, 30 feet long, with plants spaced 20 inches apart. All treatments, with the exception of the TOM- CAST treatment and the unsprayed control, received fungicide applications at seven-day intervals begin- ning three days after trans- planting and continuing through harvest. A Campbell Scientific CR10 module located on the substation was used to obtain leaf wetness and temperature measurements necessary for determining TOM-CAST applications. Disease sever- ity was assessed weekly. Tomatoes were harvested on July 19. Total yield (number and weight) was calculated. Weather conditions were relatively cool and wet for most of the experiment. Early blight was first observed in early July. Late blight became a significant problem and resulted in only one harvest. Significantly less disease .vas observed on the Bravo 825, Bravo C/M, Dacobre 27/ 27DG, and TOM-CAST-Manzate 200DF treat- ments. There were few significant differences in yield among treatments, but all were greater then the control. Bravo 825, Dacobre 27/27DG, and the TOM-CAST-Manzate 200DF treatments produced more than 10,000 pounds of tomatoes per acre. The TOM-CAST treatment required only seven fungicide applications, compared to 11 for the fixed spray treatments. At $20 per acre per application, a grower following the TOM- CAST program would have saved $80 per acre during the season. EVALUATION OF FUNGICIDES FOR CONTROL OF FOLIAR DISEASES OF TOMATOES Treatment' Foliar blight Total fruit July 8 July 14 July 21 rate/a. pct. pct. pct. lb./a. Manzate 200 DF (3 lb., fix).................................. 9.4 11.4 31.0 7,626 Manzate 200 DF (3.0 lb., TC) .............................. 4.6 4.6 15.0 10,237 Bravo 720 (2 pt.,fix).................................. 9.8 12.2 25.6 8,494 Bravo 825 (1.82 lb., fix) ............................ 5.0 6.2 16.4 10,905 Bravo C/M (5.6 lb., fix)............................... 4.0 4.2 12.2 8,611 Dacobre 27/27DG (5.6 lb., fix)............................... 5.0 5.8 14.0 10,224 Control ..................................... 61.2 74.0 80.2 1,970 'Fix = seven-day spray schedule; TC = TOM-CAST weather-timed program. 6 ALABAMA AGRICULTURAL EXPERIMENT STATION Evaluation of TOM-CAST for Early Blight Control on Tomatoes ED SIKORA, ELLEN BAUSKE, AND JIM PiTTS Alabama tomato growers may make 10 or more fungicide applications on a tomato crop to control early blight, a fungal disease that pre- fers warm, wet conditions and can cause severe defoliation and reduced yields. Growers often apply these treatments on a fixed, seven-day schedule beginning shortly after transplanting and continuing through harvest, regardless of the prevailing weather conditions. This prac- tice can waste a grower's time and money if fungicides are applied when the disease is not present or active. Each fungicide application costs approxi- mately $20 per acre. An AAES study showed that a weather-timed fungicide spray program known as TOM-CAST (Tomato Disease Fore- caster) can cut the number of applications re- quired to control early blight by almost two- thirds. TOM-CAST is currently being used in California and the north-central regions of the U.S., as well as in Canada and Mexico. Related studies since 1992 have shown re- peatedly that growers using TOM-CAST can significantly reduce the number of fungicides applied to a tomato crop in a season without resulting in a reduction in yield or fruit quality. Continuing the earlier research , AAES re- searchers in 1994 evaluated Bravo 720 and Manzate 200DF fungicides for control of early blight using both TOM-CAST and the fixed, seven-day spray schedule. At the Chilton Area Horticulture Substation in Clanton, tomatoes were trans- planted to the field on July 20. Manzate 200 DF at three pounds per acre and Bravo 720 at two pints per acre were applied according to TOM-CAST or at seven-day intervals beginning three days after transplanting and continuing through harvest. TOM-CAST uses two weather measurements: leaf wetness and air tempera- ture to assess disease risk and determine opti- mum fungicide spray intervals. Leaf wetness and temperature measurements were obtained from the fully automated weather station located on the substation (Alabama Mesonet). Early blight severity was assessed weekly. Tomatoes were harvested on Sept. 20 and 26, and Oct. 3, 11, and 18. Total yield (number and weight) was calculated. Significantly more disease was observed on the unsprayed control during the last two rat- ing periods. No significant difference was ob- served in total fruit number or weight among treatments. The TOM-CAST treatments, how- ever, required only five fungicide sprays, com- pared to 14 for the fixed spray treatments. This more efficient spraying schedule would have saved a grower $180 per acre. EVALUATION OF TOM-CAST AND A FIXED FUNGICIDE SPRAY PROGRAM WITH BRAVO 720 AND MANZATE 200DF FOR EARLY BLIGHT CONTROL ON TOMATOES Treatment' Foliar blight Total no. Total yield Sept. 13 Sept. 30 Oct. 7 pct. pct. pct. no./a. lb./a. Control .... ........................... 4.6 40.2 90.6 2,815 7,045 Manzate 200 DF (Fix) ................ 3.0 9.8 23.4 41,672 22,207 Manzate 200 DF (TC).................4.2 15.4 32.6 49,368 25,357 Bravo 720 (Fix) ........................... 2.8 8.6 27.0 35,719 17,722 Bravo 720 (TC) ........................... 3.6 13.0 27.8 32,815 17,805 1 Fix = seven-day spray schedule; TC = TOM-CAST weather-timed program. Double-cropping on Black Polyethylene Mulch: Fall Collards Following Spring Tomatoes JOE KEMBLE AND JIMMY Wr-r Despite the potential for greater yields of high quality produce, many Alabama growers have expressed concern over the high costs of producing vegetables on polyethylene mulch with drip irrigation (plasticulture). Polyethyl- ene mulch and drip irrigation lend themselves to double-cropping. In this way, material and labor costs associated with plasticulture are spread over two growing seasons. An AAES study at the E.V. Smith Research Center in Shorter is examining the effect of mulch types and varying fertility regimes (be- fore and after planting) on growth and yield of double-cropped tomatoes and collards. This three-year project also seeks to determine the economic returns and production costs for the various double-crop systems. Presently, there are no commercial recommendations for double-cropping vegetables in Alabama. Treatments are evaluated based on plant growth and development, fruit set, vine cover, and product quality and quantity. Yield was determined by weight, quality, and/or fruit num- ber of each marketable grade. In the spring tomato trial, five fertility lev- els (0, 60, 120, 180, 240 pounds of N per acre) on black plastic were compared to the conven- tional treatment for tomatoes (120 pounds of N per acre on bare ground). Bare ground plots re- ceived additional nutrients via sidedressing, while black plastic plots received nutrients via fertigation. Control plots received 50% of all N and K, and 100% of required P preplant. Black plastic plots received 30% of all N, 100% of required P (based on soil test results), and 30% of all K required (based on soil test re- sults) preplant. Proper weed, insect, and disease control was maintained. Fertilizer was injected weekly be- ginning the week of transplanting and continu- ing through final harvest. Moisture levels were monitored via switching tensiometers placed in a representative plot of each treatment. After final harvest, tomato plants are sprayed with the herbicide glyphosate, allowed to die back, and then removed. Fertility for collards was based on soil test results and desired level of fertility, so total amount injected or sidedressed was determined after soil test results were returned. Bare ground plots received preplant nutrients via sidedressing, while black plastic plots received nutrients via fertigation. In September, collards transplants were placed into previously punched holes. Proper weed, insect, and disease control was maintained. As in the spring test, irriga- tion was monitored via switching tensiometers. Presently, this study is still underway. A complete update will be available in the next Fruit and Vegetable Research Report. FRUIT AND VEGETABLE RESEARCH REPORT 7 8 ALABAMA AGRICULTURAL EXPERIMENT STATION Double-cropping on Black Polyethylene Mulch: Trellised Cucumbers Following Tomatoes JOE KEMBLE AND JIMMY WITTr Double-cropping is the production of two consecutive crops on the same land area in a successive growing season. This practice can increase efficiency by spreading costs for ma- terials and labor across two growing seasons. Trellised cucumbers return higher yields and quality, but the process of staking and tying is labor- and cost-intensive, limiting the number of growers using this system. This study exam- ined the potential of double-cropping trellised cucumbers following staked, fresh-market to- matoes in Alabama. After the final harvest of tomatoes, plants were sprayed with the herbicide glyphosate. Care was taken to prevent the spray from com- ing in contact with the plastic mulch. After the tomato plants died back, 30 pounds of N per acre from 20-20-20 were injected through the drip system. Thereafter, five pounds of N per acre were injected weekly -- alternately from 20-20-20 and potassium nitrate (13-0-44) -- con- tinuing throughout the final harvest of cucum- bers. Instead of providing new support for grow- ing cucumbers, the cucumbers used the dead to- mato plants along with the attached strings and states for support. Two weeks after the herbicide was applied, holes were punched through the plastic eight inches apart. Then, two to three seeds of three cucumber cultivars ('Centurion,' 'Hustler,' and 'Slice King') were sown to a depth of one inch. Following emergence, plants were thinned to one per hill. Proper weed, insect, and disease control were maintained. Cucumbers were har- vested every two to three days, and fruit were graded according to USDA standards. Results indicate that this is a potential sys- tem for tomato and cucumber production in Ala- bama. Overall, 'Slice King' and 'Centurion' performed similarly, each producing more and better marketable fruit than 'Hustler'. However, 'Slice King' produced more U.S. Fancy grade fruit than the other two cultivars. Vine cover, plant growth, and overall vigor of 'Slice King' was also better than that of 'Hustler' and 'Cen- turion,' and thus appeared to be more adapted to trellising. YIELD OF THREE CUCUMBER CULTIVARS IN DOUBLE-CROP EXPERIMENT Cultivar U.S. Fancy U.S. No. 1 U.S. No. 2 Cull Total marketable Total season lb./a. lb./a. lb./a. lb./a. lb./a. lb./a. Slice King................. 1,494.1 436.5 766.8 1,344.2 2,697.4 4,041.6 Centurion.......................987.2 562.7 1,129.4 1,097.6 2,679.3 3,776.9 Hustler ........................... 480.3 383.7 688.1 767.6 1,552.0 2,319.6 FRUIT AND VEGETABLE RESEARCH REPORT 9 Optimal Timing of Insecticides for Control of Pickleworm on Cucumber and Squash GEOFF ZEHNDER, TERI BRIGGS, JIMMY WITT, AND LARRY WELLS An AAES study revealed bad news for cu- cumber growers: the commonly used insecti- cide spray schedule may begin too late to pre- vent pickleworm damage. Tolerance for pickleworm damage in the pickling cucumber industry is particularly low; even a small per- centage of damaged fruit can result in rejection of the entire harvest. At flowering, growers usually spray insec- ticides on a seven-day or more frequent sched- ule to protect fruit from this damage. However, AAES researchers found pickleworm larvae in buds before the flowers had opened. Pickleworm larvae cause damage to squash and cucumbers by feeding inside the fruit. Hatch- ing larvae feed on foliage in the developing stem tips and flower buds, but later bore into the fruit where they will complete development. It is not uncommon to see a single squash fruit with five to six pickleworm entry or exit holes. Field experiments were conducted at Wiregrass Substation in Headland and E.V. Smith Research Center in Shorter. At Wiregrass, 'Vlas-Pik' cucumber seed was planted on June 13 with 35.4-inch row spacing and 9.8-inch plant spacing. As soon as plants emerged and were large enough to sample, stem tips, foliage, and flowers were exam- TABLE 1 ined for pickleworm UNDER VA larvae in randomly First spray selected areas. The first spray in each First sign of buds .................. treatment was made First sign of buds .............. First sign of buds .................. based on the pres- First open bloom ................... ence of insects or on First open bloom ................... plant growth stage; First open bloom ................... First sign of larvae in plants subsequent sprays First sign of larvae in plants were applied at four- First sign of larvae in plants to 10-day intervals. Untreated control................... All treatments were sprayed with Asana XL in- secticide at the rate of 9.6 fluid ounces per acre. Fruit were harvested every three to four days and examined for damage; fruit with at least one hole was considered damaged. At E.V. Smith, 'Gold Slice' squash was di- rect-seeded on Aug. 5. Squash was used in this test because researchers previously observed greater pickleworm damage on squash than on an adjacent planting of cucumber. Previous ex- periments showed that the initial pickleworm insecticide application must be made before first open flower. Also, the first observed pickleworm larvae on plants was within a few days of the first presence of flower buds on plants. Based on those findings, the initial spray in this study was applied when larvae were first observed; subsequent sprays were made at four- to 10-day intervals. Sprays, insect sampling and harvests were done as described for the experi- ment at Wiregrass. Overall pickleworm damage in the cucum- bers was light. However, damage in the un- treated control was severe enough to warrant rejection of the crop by the pickle processing industry; a maximum of 8.3% damaged fruit was recorded on Aug. 11 (Table 1). SPICKLEWORM DAMAGE TO CUCUMBER RIOUS INSECTICIDE TREATMENT REGIMES Frequency Pct. damage Aug. 8 Aug. 11 Aug. 15 Total .......... 4-day 0 0 0 0 .......... 7-day 0 1.1 0 0.2 ........ 10-day 0 0 0 0 .......... 4-day 0 0 0 0 .......... 7-day 2.4 1.1 0 0.8 ........ 10-day 0 0 0 0.5 .......... 4-day 0 0 0 0 .......... 7-day 0 0 0.7 0.1 ........ 10-day 0 0 0 0.1 -- 7.6 8.3 4.2 4.3 10 ALABAMA AGRICULTURAL EXPERIMENT STATION Treatments where the initial spray was ap- plied when pickleworm larvae were first ob- served in plant samples (July 13) exhibited little damage (Table 1). However, a low percentage of damaged fruit was seen in treatments where plants were not sprayed until the first open flow- ers. These results indicate that the first insecti- cide application for pickleworm should be ap- plied either at the first presence of flower buds, or at the first sign of larvae in stem tips or buds of the plants. Pickleworm infestation was severe in the squash experiment, with peak damage occur- ring on Sept. 23 and 26 (Table 2). Damage was most severe in plots treated at 10-day intervals, indicating that this interval is too long to pro- TABLE 2. PICKLEWORM DAMAGE TO SQUASH SPRAYED AT FOUR- TO 10-DAY INTERVALS BEGINNING WHEN LARVAE FIRST OBSERVED Spray interval Pct. damage Sept. 23 Sept. 26 Total 4-day ......... ........ 5.0 0 1.5 7-day .................. ........ 2.9 0 1-6- 10-day......... ............. 32.1 5.2 8.5 Untreated control...........28.5 22.2 16.3 vide effective control when the level pickleworm infestation is high. Results indi- cated that Asana applied at the first sign of lar- vae in plants and continued at four- to seven- day intervals will provide effective control of pickleworm damage. Root-Colonizing Bacteria for Control of Bacterial Wilt Disease and the Cucumber Beetle Vector GEOFF ZEHNDER, JOE KLOEPPER, CHANGBIN YAO, GANG WEI, SADIK TUZUN, RICHARD SHELBY, OYETTE CHAMBLISS, AND JIMMY WrITTr Bacterial wilt, caused by the insect-trans- mitted bacterium Erwinia tracheiphila, is a se- rious disease affecting production of crops in the cucumber family in the eastern U.S. Bacte- rial wilt is particularly destructive to cucum- bers and muskmelons; squash and pumpkin are susceptible but are not affected as severely. Fungicides are not effective against bacte- rial diseases, so the primary control method for bacterial wilt involves use of insecticides tar- geted against cucumber beetles that spread the pathogen from plant to plant. However, cucum- ber beetle infestations are impossible to con- trol completely with insecticides because beetles are highly mobile and continually in- vade cucumber plantings from adjacent fields or weedy areas. In 1993, AAES scientists began evaluating specific strains of root-colonizing bacteria, also known as plant-growth promoting rhizobacteria (PGPR), to determine how well they control the bacterial wilt disease and what effect they have on the cucumber beetle. These studies have shown the beneficial properties of PGPR when applied to cucumbers as a seed treatment or a root-drench application. Colonization by cer- tain PGPR strains not only increases plant growth, it can also enhance a plant's defense mechanisms. In field experiments at the E.V. Smith Re- search Center in Shorter, PGPR treatments were compared to an insecticide control (weekly sprays with Asana XL insecticide) and an un- treated control. 'Straight 8' cucumber seeds were dipped into solutions containing PGPR bacteria before planting. Cucumber yields from the PGPR-treated plants were higher than yields in the insecti- cide-treated and untreated controls (Table 1). In 1994, the percentage of wilted vines was seven to nine times greater in the untreated plots, and three to four times greater in the in- secticide-treated plots, compared to the PGPR treatments. Unexpectedly, numbers of cucum- 10 ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 1. EFFECT OF PGPR TREATMENT ON CUCUMBER YIELD, CUCUMBER BEETLE NUMBERS, AND BACTERIAL WILT SYMPTOMS IN FIELD EXPERIMENTS (1993 AND 1994) Treatment' Fruit wt. Beetles/plant Wilted vines/plant 1993 1994 1993 1994 1994 lb./plot lb./plot no. no. pct. 89B-61 .......................................... 82.25 NT 2 0.61 NT NT 90-166 ............................................. 79.16 61.96 0.44 2.3 2.6 INR-5 .............................................. 72.10 NT 0.56 NT NT INR-7..............................................81.81 58.43 0.73 2.9 3.4 Insecticide control..........................64.83 48.29 0.89 3.6 11.5 Untreated control............................ 60.20 45.86 1.73 5.4 24.6 'Four PGPR strains were evaluated in 1993 (89B-61, 90-166, INR-5, and INR-7). Only 90-166 and INR-7 were evaluated in 1994. 2 NT = not tested. ber beetles in the PGPR treatments were not only lower than in the untreated control, they were also lower in insecticide-treated plots. In the greenhouse experiments at the AU Plant Science Center, cucumber beetles infected with the bacterial wilt pathogen were released to feed on plants inside screened cages. For 23 days, beetles had a choice between PGPR- treated and untreated plants. Beetle feeding on cotyledons (earliest leaves on a seedling) of PGPR-treated plants was significantly lower than on untreated plants (Table 2). Also, the average numbers of wilted leaves per plant were significantly lower on PGPR-treated plants. To explain the apparent non-preference of beetles for PGPR-treated plants, cotyledon leaves from PGPR-treated and untreated plants were analyzed to determine plant concentrations of the beetle feeding stimulant, cucurbitacin, which is present in cucumber and in other spe- cies of cucurbits. Results indicated that cucum- ber treated with some PGPR strains contained reduced concentrations of cucurbitacin. These results indicate that PGPR-induced protection against bacterial wilt disease works on two levels. First, PGPR protects the plants against cucumber beetle feeding, thereby reduc- ing spread of the disease. Second, PGPR-treated plants are more resistant or tolerant to bacterial wilt infection after the pathogen is introduced. PGPR treatment represents an exciting and environmentally friendly tool for use in pest management. Unlike most other biological con- trol agents, PGPR bacteria can protect against a wide spectrum of pathogens and/or pests. This advantage was demonstrated in recent AAES experiments, where two diverse pests (a bacte- rial pathogen and an insect) were controlled by PGPR. TABLE 2. CUCUMBER BEETLE FEEDING DAMAGE TO CUCUMBER AND SPREAD OF BACTERIAL WILT DISEASE IN GREENHOUSE CAGE EXPERIMENTS Days after beetle release Pct. cotyledon leaf damage Avg. no. wilted leaves/plant Untreated INR-7 Untreated INR-7 3 .................................................... 10.8 1.7 0.00 0.00 7 .................................................... 20.6 8.1 0.00 0.00 11 .................................................. 54.2 25.5 0.25 0.00 15 ................................................ 100.0 74.2 0.50 0.00 19 .............................. .................. 100.0 91.6 0.94 0.00 23 ................................................ 100.0 100.0 1.88 0.06 FRUIT AND VEGETABLE RESEARCH REPORT 11 12 ALABAMA AGRICULTURAL EXPERIMENT STATION Reflective Mulches Aid in Control of Aphid-Borne Viruses in Summer Squash JAMES BROWN AND GEORGE BOYHAN Aphid-transmitted viruses can devas- tate summer squash yields and render sur- viving crops unmarketable by creating 0 mottled green patterns on the fruit. With Trc many of these mosaic viruses, aphids only need to probe the plant tissue for a short Sil period to transmit the virus. Therefore, Sil Wh using insecticides to control the virus car- Ye riers is ineffective; even the few aphids Bl left after spraying can spread enough Bl Bai pathogens to destroy a summer squash Ba crop. Specific environmental stimuli cue these aphids to find suitable plants on which to feed. This phenomenon can be exploited with the use of reflective mulches, which are be- lieved to confuse the insects by reflecting sun- light. AAES studies showed that using reflec- tive mulches delays the onset of mosaic virus symptoms, thus increasing yields. Summer squash are generally harvested many times dur- ing the season while the fruit are young, so de- laying symptom onset is particularly beneficial. In a two-year study, silver plastic mulch without pesticide applications produced the highest yields of summer squash (Table 1). Additional work found that squash variety had no effect on the percent of virus infection, but benefits based on mulch type continued up to 55 days after transplanting (Table 2). Recently, Asgrow Seed Co. in cooperation with Cornell University released two new cul- tivars, Freedom II and Prelude II, which have genetically engineered virus resistance. Al- though these varieties are not resistant to all viruses that affect summer squash, they offer a new approach to this problem which may pre- clude the need for reflec- CENT tive mulches. Further YMPTOMSstudy is planned to evalu- after transplanting ate the interaction of these 49 55 new varieties with the use 44 40 of reflective mulches. 61 53 TABLE 1. EFFECT OF DIFFERENT COLORED MULCHES, BARE GROUND, AND INSECTICIDE APPLICATIONS )N MARKETABLE YIELD OF SUMMER SQUASH, 1989-1990 eatment Marketable yield lb./a. ver plastic ........................................ ..................... 9,589 ver plastic w/ insecticide ....................................... 8,697 hite plastic ......................................... .................... 6,9 13 llow plastic ........................................................... 6,868 ack plastic ........................ ......................... 5,932 ack plastic w/ yellow edge ..................................... 6,333 re ground w/ insecticide......................................... 4,772 re ground ............................................... 4,282 TABLE 2. EFFECT OF MULCH TYPE ON PEI OF SUMMER SQUASH PLANTS FREE OF VIRUS S Mulch type Percent virus free at 27-55 days 27 35 42 Black Plastic .......................... 98 77 73 Silver Plastic .......................... 99 96 92 12 ALABAMA AGRICULTURAL EXPERIMENT STATION FRUIT AND VEGETABLE RESEARCH REPORT 13 Potential New Watermelon and Cantaloupe Varieties GEORGE BOYHAN, ERIC SIMONNE, JOE NORTON, DAVE HIMELRICK, BENJAPORN TANGSUKKASEMSAN, AND IRMA CHANG Two advanced watermelon breeding lines and an advanced cantaloupe breeding line show promise as potential new varieties in Alabama. The watermelon varieties AW-82-50ss and AU- AS and the cantaloupe variety AC-82-37RNL were developed in the long-standing AAES plant breeding program. AW-82-50ss is a small-seeded selection of the AU-Sweet Scarlet watermelon, which is re- sistant to several foliar diseases and has supe- rior flavor. This advanced line has the same positive characteristics of the parent line, but its seed are about half the size of AU-Sweet Scarlet seed. Also, it produces slightly smaller fruit than AU-Sweet Scarlet, a characteristic generally associated with small seed size. AU-AS, an Allsweet-type watermelon, is long and dark green with a light green stripe. It YIELD AND FRUIT CH has bright red flesh, small seed, and en- hanced flavor. This line was developed lb. from backcrossing AU-AS ........................... ..... 9, and recurrent selec- Fiesta ............................... 12, AW -82-50ss .................... 16,' tion with germplasm Crimson Sweet................ 19,( that possessed high levels of disease re- AC-82-37RNL ................ 16, ~sistance.PMR 6 ............................. 10, sAnCe8-7'Results for watermelons are AC-82-37RNL and E.V. Smith Research Cer is a heavily netted Center in 1995. cantaloupe with 2 Soluble solids is a measure fruit. good shipping qual- ity and excellent disease resistance. It produces somewhat larger-than-average, western-type fruit. Both AC-82-37RNL cantaloupe and AW- 82-50ss watermelon tested favorably in a con- sumer acceptance study at two supermarket lo- cations in Auburn. At this time, only preliminary data are avail- able on these melons (see table). More exten- sive evaluation of these lines is planned for 1996. In other melon research, work continued in an effort to breed a commercial watermelon with resistance to zucchini yellow mosaic vi- rus and watermelon mosaic virus. This experi- mental line was backcrossed with AU-Producer, a Crimson Sweet type watermelon with mul- tiple resistance to foliar diseases. ARACTERISTICS OF WATERMELON AND CANTALOUPE 1 eld Type Melon Soluble weight solids 2 /a. lb. pct. Watermelon 943 Allsweet 18 9.3 697 Allsweet 9 6.8 739 Crimson Sweet 24 10.3 627 Crimson Sweet 14 9.6 Cantaloupe 067 Western 4 9.5 726 Western 4 10.7 combined from studies at Sand Mountain Substation in 1994 nter in 1995. Cantaloupe results are from E.V. Smith Research of fruit sweetness. The higher the percentage, the sweeter the FRUIT AND VEGETABLE RESEARCH REPORT 13 Double-cropping on Black Polyethylene Mulch: Fall Broccoli Following Spring Bell Peppers JOE KEMBLE, BOBBY BOOZER, AND JIM PIrrs Despite the potential for BELL PEP greater yields of high quality pro- C duce, Alabama growers have ex- pressed concern over the high Treatment costs of producing vegetables on polyethylene mulch with drip ir- rigation (plasticulture). Polyeth- 0 lb. N....... ylene mulch and drip irrigation 60 lb. N.............. lend themselves to double-crop- 120 lb. N ........... ping. In this way, material and la- 180 lb. N ......... bor costs associated with 240 lb. N ........... plasticulture are spread over two growing seasons. However, there 120 lb. N. are no commercial recommenda- tions for double-cropping vegetables in Alabama. An AAES study is examining the effects of various fertility regimes (before and after plant- ing) and mulch types on growth and yield of double-cropped bell peppers and broccoli. The study is also designed to determine the economic returns and production costs for the various double-crop systems. This three-year experiment is being conducted at the Chilton Area Horticul- ture Substation in Clanton. Treatments were evaluated based on plant growth and development, fruit set, vine cover, and product quality and quantity. Yield was deter- mined by weight, quality and/or fruit number of each marketable grade. In the spring bell pepper study, black plastic plots with fertility levels ranging from 0-240 pounds of N per acre were compared to the conventional treatment for bell peppers, which is 120 pounds of N per acre on bare ground. Bare-ground plots re- ceived additional nutrients via sidedressing, while black-plastic plots received nutrients via fertigation. Control plots received 50% of all N and K and 100% of required P preplant. Black plastic plots received 30% of all N, 100% of required P (based on soil test results), and 30% of all K required (based on soil test results) preplant. Proper weed, insect, and disease control was maintained. Fertilizer was injected weekly begin- PER YIELDS OF FIVE PLASTIC MULCH TREATMENTS iOMPARED TO CONVENTIONAL PRODUCTION U.S. U.S. Cull Total Total Fancy No. 1 marketable season lb./a. Ib./a. lb./a. lb./a. lb./a. Black plastic 1,018.7 2,624.0 1,180.6 6,728.3 7,908.9 2,320.9 5,397.5 1,178.2 12,277.7 13,455.9 4,804.8 7,525.8 1,459.0 16,653.1 18,112.1 4,417.3 7,501.7 12,17.2 15,962.4 17,179.6 5,454.2 6,994.2 1,538.4 16,744.9 18,283.3 Bare ground 2,621.9 6,112.9 13,17.9 11,437.8 12,755.7 ning the week of transplanting and continuing through final harvest. Moisture levels were moni- tored via switching tensiometers placed in a repre- sentative plot of each treatment. After final harvest, plants were sprayed with the herbicide glyphosate, allowed to die back, and then removed. Initial data in this ongoing study indicates that plasticulture production using total nitrogen rates of 120, 180, and 240 pounds produced market- able bell peppers of higher quality and in greater quantity than the conventional, bare-ground treat- ment (see table). These three plasticulture treat- ments also produced more U.S. Fancy Grade fruit, which return a higher price in the fresh market. 1995 data will be compared to results from next year's study. In the fall study, fertility for broccoli was based on soil test results and desired level of fer- tility, so total amount injected or sidedressed was determined after soil test results were returned. Bare-ground plots received preplant nutrients via sidedressing, while black-plastic plots received nutrients via fertigation. In September, broccoli transplants were placed into previously punched holes. Proper weed, insect, and disease control was maintained. Moisture levels were monitored as in the spring study. More information on the results of this portion of the study will follow in the next Fruit and Vegetable Research Report. 14 ALABAMA AGRICULTURAL EXPERIMENT STATION Lipid-Based Edible Coatings Improved Shelf Life and Consumer Acceptance of White Bell Peppers AMY SIMONNE, CHRISTY MOORE, ERIC SIMONNE, ROBERT HAGENMAIER, NANCY GREEN, FLOYD WOODS, AND RONALD EITENMILLER Modified- and con- EFFECT OF BELL PEPPER COATING ON WATER Loss AND SENSORY EVALUATION trolled-atmosphere pack- aging increase vegetable Treatment Percent Firmness' Overall Color' Glossiness' shelf-life by controlling water loss preference' water and gas exchanges Control ..................... 9.8 1.6 1.3 3.6 2.9 Wax A (8%) ............. 3.4 4.2 3.6 3.9 3.1 between the product and Wax B (15.2%) ........... 3.4 4.3 4.0 4.5 4.6 surrounding environ- Wax A (16%)............. 2.9 4.1 3.6 4.2 3.0 ment. Coating vegetables 'These sensory characteristics were rated on a five-point scale: 1 = worst; 5 = best. with edible films pro- vides the same benefits, but there is no solid waste once. Coated peppers from all treatments were to discard with this method. Edible coatings are stored in open boxes under accelerated storage commonly made from polysaccharides, proteins, conditions at 25 0 C in normal indoor lighting for or lipids. Antioxidants and antifungal and anti- 20 days or until coated peppers lost more than microbial substances can also be incorporated into 7% of their original weight. the coating formulation to reduce rancidity and Fifteen experienced panelists were asked to contamination. evaluate pepper samples at three-day intervals An AAES study found that selected lipid- throughout the course of the experiment. Panel- based, edible films improved the shelf life of ists rated the coated peppers as firmer than the white bell peppers and delayed color change, loss uncoated peppers (see table). Wax B received the of firmness, and loss of weight during storage. highest scores for glossiness and color, and the Coated peppers were well accepted by the trained uncoated control, the lowest. For overall accept- panelists. This study shows that lipid-based ed- ability, uncoated peppers were rated the lowest, ible coatings for bell peppers have potential for and among the coated peppers, differences in commercial application. overall acceptability were not significant. Immediately after harvest, approximately 100 Coating significantly reduced water loss of unblemished 'Dove' and 'Ivory' bell peppers of bell peppers. Although, the effects of the three the US#1 or US#2 grades were washed and disin- coatings on water loss was not significantly dif- fected with chlorinated water. Peppers were dried ferent, Wax A (16%) reduced water loss the most, and randomly assigned to four treatment groups, but Wax A (8%) was not significantly different three of which involved various coating formula- in preventing water loss. Overall, coated peppers tions and a fourth that was left uncoated as a con- lost 5% of their original weight by day 12; trol. whereas, the uncoated peppers lost 15%. Nor- "Wax A" was a 16% candelilla wax, with mally, peppers are considered unmarketable af- 2.5% oleic acid, 0.8% palmitic acid, 0.3% gela- ter losing more than 7%. The concentration of all tin, 200 parts per million (ppm) antifoaming coatings seemed to be adequate to reduce water agent, morpholine, ammonia, and water. One loss and minimize water stress. treatment used the full 16% Wax A, while a sec- Results suggest that coating does not affect ond used Wax A diluted 1:1 with water to make the loss of ascorbic acid from peppers. Ascorbic an 8% formulation. "Wax B" was a 15.2% acid content of control peppers appeared to in- candelilla wax, with 0.9% oleic acid, 1.5% palm- crease slightly after 14 days. However, this find- itic acid, 0.7% soy isolate, 200 ppm antifoaming ing may be due to the concentration effect; un- agent, ammonia, and water. Peppers were sub- coated peppers lost more moisture, so the rela- mersed into the appropriate coating solutions tive amount of ascorbic acid would increase. FRUIT AND VEGETABLE RESEARCH REPORT 15 16 ALABAMA AGRICULTURAL EXPERIMENT STATION Chitosan Coating Delays Postharvest Ripening of Bell Peppers FLOYD WOODS, RABAH AYNAOU, JAMES BROWN, ERIC SIMONNE, SADIK TUZUN, AND TRACEY LAND Bell peppers are typically refrigerated after har- vest, but since the fruit are sensitive to chilling, long- term cold storage is not feasible. AAES researchers found that coating peppers with a material known as chitosan delays ripening. Fruit ripening is characterized by changes in tex- ture and carbohydrate metabolism. Bell pepper soft- ening is generally attributed to degradation of cell wall biochemicals, primarily the water-soluble car- bohydrate pectin. This process is associated with increased activity of Polygalacturonase, an enzyme responsible for softening fruits and vegetables. Chitosan, which acts as a selective barrier to diffuse gases and maintain a water-saturated environment, is hypothesized to significantly alter pectin content and enzyme activity in the cell wall during ripening. Peppers were harvested at the mature green stage and surface-sterilized with a .5% solution of com- mercial bleach before postharvest treatment. Peppers were individually hand dipped in 1.5% chitosan so- lution, drained, and allowed to surface dry before storage. Control peppers were submersed in a .1% solution of Tween 80 and allowed to surface dry before storage. Peppers were stored at 13 0 C and 85% relative humidity for approximately 20 days. PG Activity 0.15 - 0.1 0.05 0 4 8 12 15 20 Days in storage Figure 1. Chitosan coating generally reduced the activity of polygalacturonase (PG), an enzyme associated with cell wall degradation in ripening fruit. As polygalacturonase activity decreases, peppers age slower. Following the 20-day storage, overall quality and appearance of chitosan-treated fruit was superior to uncoated fruit. Chitosan-treated fruit appeared firmer and more uniform in color. They suffered less postharvest decay and wilting. Chitosan application caused an initial decline in Polygalacturonase ac- tivity within the first four days of storage (Figure 1). It also had a marked effect on pectin levels, and thus on fruit ripening (Figure 2). With progressive fruit softening, both chitosan- treated and control fruit showed an increase in Polygalacturonase activity, reaching maximum ac- tivity by day eight. However, Polygalacturonase activity in chitosan-treated fruit was significantly lower. After the eighth day, Polygalacturonase ac- tivity in treated and control fruit declined rapidly and remained near levels observed initially. Throughout the ripening period, chitosan-treated fruit tended to have lower Polygalacturonase activity. Water-soluble pectin content during the first four days in storage remained similar for both treatments. During day eight, tissue softening was higher for the control. This pattern of ripening remained throughout storage until day 20, when the chitosan- treated peppers were softer than control fruit. WSP Content 5 - 0 4 8 12 15 20 Days in storage Figure 2. Chitosan coating had a significant effect on wa- ter-soluble pectin content (WSP). As water-soluble pectin increases, peppers become softer. 16 ALABAMA AGRICULTURAL EXPERIMENT STATION FRUIT AND VEGETABLE RESEARCH REPORT 17 Response of Bell Pepper Yields to an Irrigation Scheduling Model ERIC SIMONNE, VANESSA DROUOT, JIMMY WITT, AND JOE KEMBLE Rainfall patterns in Alabama are irregular, so supplemental irrigation is needed to ensure a con- tinuous supply of water to fast-growing vegetable crops such as bell pepper. Often, farmers begin irri- gation when the soil feels dry or when plants begin to wilt. However, this approach often results in in- adequate water application, possible nutrient leach- ing, and subsequent yield reduction. AAES research has developed a system for cal- culating daily water budgets for overhead irrigated bell peppers. This irrigation scheduling model is based on actual crop water use and can be used to adjust water applications to weather demand and crop age. Under recommended nitrogen (N) appli- cations, bell pepper yields were highest in plots re- ceiving the amounts of water indicated by the model. Experimental bare-ground plots were designed to test the effect of various irrigation rates: the rate recommended by the water budget model, along with several rates higher and lower than the recommended amount. The study also examined two N rates. To- tal N, including preplant and sidedress applications, was 112 pounds per acre for the low-N treatment, which corresponded to the medium recommended rate. The high-N treatment was 170 pounds per acre. The herbicide Treflon HEC was applied before planting at the rate of one pint per acre. Five-week-old 'X3R Camelot' were transplanted on May 23. Three irrigations were applied 1-6 days after transplanting (DAT) to ensure stand uniformity. Irrigation accord- ing to the water budget model began seven DAT. The irrigation model used rainfall and evapora- tion data obtained from the Agricultural Weather Service at AU. This information is modified by a formula based on the age of the pepper crop to de- termine when irrigation should be applied and at what rate. A complete description of the model is beyond the scope of this publication, but more in- formation is available from the authors. Under low-N fertilization (figures 1, 2), plots irrigated at the rate predicted by the model had the optimum marketable yield and number of peppers. Results showed that an optimum irrigation rate ex- ists for bell peppers. Yield reductions may be ob- served with insufficient or excessive water applica- tions. Under high-N fertilization, the highest water application rate may not have been sufficient to op- timize bell pepper yield. Results of this one-year study were not sufficient to determine the optimum water application rate under high-N fertilization. Marketable number 200,000 r 150,000 j 100,000 50,000 -p / / / Ing the /Experi/st te e /mmend/ rrrlrC\b ~ / ?ep 00 woo - - f 14 4 Marketable weight 25 .1- 20 15 10 5 S High N, marketable number - -- Low N, marketable number I I 1 1 1 0 25 50 100 Irrigation gradient 150 25 50 100 Irrigation gradient Figures 1-2. An irrigation gradient of 100% represents the amount predicted by the water-budget model; other gradients, both higher and lower than this recommended rate were evaluated. Marketable number is measured per hectare (multiply by .4 to calculate number per acre). Weight is measured in metric tons per hectare (multiply by .446 to calculate English tons per acre). High N is 170 pounds per acre; Low N is 112 pounds per acre. 150 FRUIT AND VEGETABLE RESEARCH REPORT 17 18 ALABAMA AGRICULTURAL EXPERIMENT STATION Subjective and Objective Evaluation of Color in Bell Peppers ERIC SIMONNE, JOHN EASON, JOE LITTLE, JIM PITTS, JOHN OWEN, MARVIN RUF, AND JOE KEMBLE Retail price for colored peppers is usually -three to five times that of green peppers, but a lack of information about the color descriptions of such varieties can make marketing them a tricky proposition. An AAES study was conducted to define color changes of new colored bell pep- per varieties. Color characteristic and uniformity are im- portant attributes of bell peppers. For wholesale, only peppers of the same and uniform color can be mixed for shipment. Typically, peppers are green when immature, ripen into a partly red fruit, and finally become fully red. However, this se- quence of color changes does not apply to some new varieties. The initial fruit color may be white or purple, instead of green. Some varieties may be yellow or orange at maturity. Others express more than two fully colored stages; initially green, they become brown or black, before turning red. Using fully colored, fancy and US#1 peppers from AAES bell pepper variety trials at four Ala- bama locations, a subjective description of the skin color was based on visual observation and information provided by seed suppliers. Color changes were described using a five-color-stage scale. Also, a chromameter (Minolta Spectropho- tometer model CM-2002) was used to objectively measure color parameters during each stage. Coloration affected either the skin alone, or both the skin and flesh. For green, red, yellow, orange, or white peppers, skin and flesh colors were simi- lar. However, the flesh of purple varieties was white; that of brown and black fruits was green. For each variety, visual observation did not permit the de- tection of differences between peppers grown at dif- ferent locations (Table 1). Chromameter readings suggest that location, and therefore growing condition, did not affect color development (Table 2). However, variety and stage of development did significantly affect objective color measurements. Most importantly, color measurements taken with the chromameter were in good agreement with the subjective, ver- bal descriptions. Therefore, chromameter mea- surements are not systematically necessary when referring to bell pepper colors. TABLE 1. VISUAL DESCRIPTION OF COLOR STAGES FOR SELECTED VARIETIES OF BELL PEPPER VARIETIES Variety Location' Fruit Color 2 1 2 3 4 5 Black Bird..................... CAHS, PS, SMS green black -- red deep red Blue Jay........................ CAHS, PS, SMS white-green purple orange red deep red Cardinal ........................ CAHS, SMS green -- -- red deep red Chocolate Beauty ......... CAHS, LCPS green brown deep brown red deep red Dove.............................. CAHS, PS, SMS green-white white orange red deep red Golden Bell................... CAHS, SMS, LCPS green . yellow orange Ivory.............................. CAHS, PS, SMS green-white white -- yellow deep yellow King Arthur .................. CAHS, SMS, LCPS green -- -- red deep red Klondike Bell ............... CAHS, SMS, LCPS green . yellow deep yellow Oriole ............................ CAHS, SMS, LCPS green -- -- yellow orange Orobelle ........................ CAHS, LCPS green yellowdeep yellow 'CAHS = Chilton Area Horticulture Substation, Clanton; PS = Piedmont Substation, Camp Hill; SMS = Sand Mountain Substation, Crossville; and LCPS = Lower Coastal Plain Substation. 2 Color changes were described using a five-color-stage scale. Stages 1 and 4 described the initial and final fruit color, respectively. Stage 5 corresponded to an apparently overripe color. Stages 2 and 3 corresponded to intermediate colorations; not all peppers had intermediate stages. The typical commercial color is underlined. 18 ALABAMA AGRICULTURAL EXPERIMENT STATION FRUI ANDVEGEABL RESARCHREPOT 1 Measurements from the chromameter can be used in a complex mathematical formula to cal- culate numerical expressions of all visible col- ors. These color expressions are measured with three values -- "L," "a," and "b." "L" is measured on a scale of 0-100, where 0 is black and 100 is white; the lower the "L" value, the darker the pep-- per. Value "a" represents a scale from green to red, while "b" represents a scale from blue to yel- low. Negative "a" values mean that a pepper has some percentage of green, while positive "a" val- ues mean that it has some percentage of red. Like- wise, negative "b" values indicate a pepper has some percentage of blue, and positive "b" values indicate that it has some percentage of yellow. The larger the numbers, the greater the percent- age of the given color; in other words, "-50 a" would have a large percentage of green. For ex- ample, Orobelle at stage 5 was described in Table 1 as being deep yellow. In Table 2, Orobelle has an "L" value of 53, which means it is moderately dark; an "a" value of 18, which means it reflects a small amount of red; and a "b" value of 30, which means it reflects a fairly large amount of yellow. Colors observed in this study were in good agreement with the color description provided by seed suppliers. Colors such as purple, brown, and black remained uniform for several days and af- fected only the skin of the fruit. It was possible to provide a verbal definition of the different stages of uniform color for selected bell pepper varieties. Each stage was clearly defined and vi- sually identifiable. Color descriptions will help producers in se- lecting bell pepper varieties of similar colors and in harvesting for a specific color stage. Another important factor is that peppers of the same vari- ety grown at different locations can be mixed for shipping and still meet requirements for color uniformity. Findings from this study will also al- low scientists to use varieties with untypical col- ors as model systems in physiology studies on fruit ripening, fruit composition, and pigment synthesis instead of the traditional green-to-red varieties. TABLE 2. OBJECTIVE PARAMETERS OF COLOR STAGES FOR SELECTED VARIETIES OF BELL PEPPER Stage' L 2 a 2 b 2 1 ............... 33 2 ................ 21 4-.............. 26 1 .................. 42 2 ...................24 3 ...................39 4 .................. 28 1 .................. 37 4 ...................42 5 ...................44 1 .................. 28 4 .................. 26 2 .................. 25 3 .................. 23 4 .................. 31 5 .................. 28 1 ................... 55 2 .................. 56 3 .................. 39 4 .................. 28 4 .................. 49 5 .................. 42 1 .................. 53 2 ...................50 4 ...................53 5 ................... 41 1 .................. 29 4 ...................26 5 ...................33 1 .................. 29 4 .................. 48 5 .................. 43 1 .................. 32 4 .................. 39 5 .................. 39 1 .................. 33 4 .................. 51 5 ................... 53 Black Bird -5 0 20 Blue Jay -2 4 23 23 Canary -7 3 10 Cardinal -5 19 Chocolate Beauty 7 4 30 21 Dove -2 -2 23 25 Golden Bell 9 23 Ivory -5 -1 0 9 King Arthur -6 26 34 Klondike Bell -6 10 9 Oriole -5 18 23 Orobelle -6 12 18 0 7 14 -2 18 10 15 20 22 8 7 5 2 11 9 18 21 16 10 26 22 22 20 25 20 11 9 15 10 26 21 11 19 19 13 28 30 'Color changes were described using a five-color-stage scale, as described in Footnote 2 of Table 1. 2 See text for definitions of L, a, and b. I FRUIT AND VEGETABLE RESEARCH REPORT 19 B 20~~~a ALBMAARIUTRAFXPRMETSaT-%ION.FII Two New Pinkeye Southernpeas Released OYETTE CHAMBUSS AND GENE HUNTER The Alabama Agricultural Experiment Station has released two new pinkeye southernpeas -- 'Alagreen Pinkeye' and 'Pickworth Pinkeye' -- which have great l potential for sale in several markets. Seed Co Co should be available to Alabama seedsmen c., by the 1998 growing season. Kia 'Alagreen Pinkeye' has a distinguish- Mi: Pin ing combination of a persistent green seed Pin coat and a distinct, non-bleeding pink eye. AR These characteristics give it a clean appear- Sar ance without the gray shadow below the eye Tex which is present in most pinkeyes. Pic 'Alagreen Pinkeye' is well suited for the fresh-market. Ala 'Pickworth Pinkeye' was released be- (w cause of its special appeal to pick-your-own wa and consumers, as well as fresh-market produc- are tion for wholesale lots in the pod or retail 2 Av sale of shelled peas. It is distinguished from 'Alagreen Pinkeye' by the presence of both green and white dry seeds. Approximately half of its plants produce a dry green seed coat, while the other half produce a white seed coat. When harvested at the mature green to early dry stage, this mixture produces a pleasant blend of green and white peas. Plants of both varieties have an erect, deter- minate growth habit; are approximately 20 inches in height; and produce limited lateral vines. Pods are slightly curved, concentrated above the plant, have a glossy surface, and are green, changing to reddish-purple at the mature green stage. The pods average 10 inches in length and almost a half inch in diameter. They are slightly constricted about the seed and produce an average of 14 seed per pod. The seed are medium to large (18-24 grams per 100 seed) and are kidney shaped. If pods re- main in the field 10-14 days after drying, the per- sistent green seed coats will bleach. Significant bleaching can occur even within the first week after drying. 'Alagreen Pinkeye' was entered in the South- ern Cooperative replicated trials in 1991 and 1992 in Alabama, Arkansas, Louisiana, Missouri, South PINKEYE SOUTHERNPEA VARIETY TRIALS IN ALABAMA: AVERAGE YIELDS FOR 1992-1994 1 try EVSRS NAHS WS rona .................... .............. 2,142 2,003 1,582 ronet ........................... ...... 2,143 2,598 1,786 T. Pinkeye Purplehull ............ 2,143 2,833 1,158 awah .................. ............... 2,158 2,022 1,287 ssissippi Pinkeye ............ 2,936 2,874 2,465 keye Pinkpod...........2,180 2,205 1,543 ikeye Purplehull-BVR...........2,138 2,004 930 -92-552 ..............-- -- 1,8242 ntee Early Pinkeye ................. 2,295 2,322 1,5972 xas Pinkeye ....... ............... 1,753 1,765 1,210 agreen Pinkeye .... ................ 2,000 2,341 1,761 kworth Pinkeye .............. 2,180 2,190 1,729 ials were conducted at E.V. Smith Research Center (EVSRS), North bama Horticulture Substation (NAHS), and Wiregrass Substation S). Fresh shelled yield was measured in pounds per acre. Yield s based on once-over harvest when 80% of pods were dry. EVSRS J NAHS yields are based on three years of data, while WS yields based on two years. verage is based on one year of data. Carolina, Tennessee, and Texas. In 1991, it was the highest yielding of four pinkeye breeding lines in the trial, but yielded less than Pinkeye Purple Hull-BVR, the commercial check. In 1992 it was the lowest yielding of five pinkeye lines, and yielded less than the check. Its yield is adequate (about a ton per acre) for its use in the frozen food trade, since it can be marketed as a specialty item to enhance grade. With the exception of Louisiana and Texas, 'Alagreen Pinkeye' seems fairly well adapted across the South. In Alabama, both varieties were entered in a three-year southernpea variety trial (1992-1994) with 10 other pinkeyes (see table). Average three- year yield of 'Alagreen Pinkeye' ranked third, fourth, and eighth at the Wiregrass Substation in Headland (only two years), North Alabama Hor- ticulture Substation in Cullman, and E.V. Smith Research Center in Shorter, respectively. In the same trials, 'Pickworth Pinkeye' ranked fourth, seventh, and third. The rank of check varieties commonly used by the industry ranged from the first to eleventh across locations. 20 ALABAMA AGRICULTURAL EXPERIMENT STATION The Value Of Host Plant Resistance in Controlling Cowpea Curculio in Southernpeas GENE HUNTER, OYETTE CHAMBULISS, AND LARRY WELLS Damage caused by the cowpea curculio, a small black weevil, can severely Timit the mar- ketability of southernpeas sold for processing or offered in fresh markets and pick-your-own op- erations. AAES studies found that southernpea lines originating from an Auburn-developed breeding line were most resistant to curculio dam- age. Using these resistant varieties proved to be more effective than using insecticides to reduce curculio damage. Adult cowpea curculio damage southernpeas by feeding on immature seeds, leaving charac- teristic "stings" on seeds and pods. Curculio eggs are deposited on seeds in the early mature-green stage, generally one egg to each seed. After lar- vae feed on dry seed, they chew exit holes in the pods and fall to the soil where they pupate. At the Wiregrass Substation in Headland, nine southernpea varieties and one breeding line were planted on June 3. Treatments included THIODAN 3EC and PENNCAP-M at the recom- mended rate of one pound of active ingredient per acre and at one-quarter the recommended rate. Control treatments impact of tractor traffic, which could affect insect feed- ing. One included no insecticide but had tractor traffic; the other received no insecticide or tractor traffic. Chemicals were ap- plied three times at five-day intervals from first blooms. Southernpeas were harvested when 80% of the pods were dry. Harvested were set up to illustrate the pods were kept in paper bags in metal trays until all curculio larva emerged. A 50-pod sample from each plot was examined for curculio-damaged seed, number of sound seeds, number of larval exit holes, and weight of sound seeds. There was no difference between the effec- tiveness of treatments in reducing the number of seeds damaged by the cowpea curculio (see table). When the average percentage of damaged seed for the two control treatments (12.2% damage) was compared to each insecticide treatment, only the one-pound-per-acre Pencap-M treatment dif- fered significantly (7.3% damage). However, varieties differed in the percentage of curculio-damaged seed 'California Blackeye #5,' which is known as the standard for curculio susceptibility, suffered the most damage. 'Caro- lina Cream,' 'Bettergreen,' and the breeding line CR-22-2-21 had the least amount of damaged seed. 'Freezegreen' also was fairly resistant. These four lines with the least amount of damage originated from the breeding line Alabama 963- 8, which was developed as part of Auburn's cow- pea curculio resistance breeding program. PERCENTAGES OF SEEDS DAMAGED BY COWPEA CURCULIO IN SOUTHERNPEAS USED TO EVALUATE THE VALUE OF HOST PLANT RESISTANCE Variety Check w/o Check w/ PENNCAP-M THIODAN 3EC Avg. traffic traffic .25 lb./a. 1 lb./a. .25 lb./a. 1 lb./a. AUBe (blackeye) ................. 9.4 12.7 7.6 2.5 8.4 9.9 8.4 Bettergreen (cream).............3.9 4.9 6.1 3.8 4.5 5.2 4.7 Bettergrow Blackeye...........7.6 10.9 7.1 2.3 10.0 6.9 7.5 California Blackeye #5'....45.9 48.1 37.4 36.1 47.5 40.8 42.7 Carolina Cream.................... 8.5 3.6 3.3 1.3 4.0 1.6 3.7 Carolina Crowder .............. 11.5 10.0 15.6 5.6 7.4 6.5 9.5 CR-22-2-21 ........................... 5.9 8.3 5.6 3.1 5.5 6.4 5.7 Freezereezegreen (cream)............6.7 6.9 9.7 6.7 6.1 6.6 7.1 Pinkeye Purplehull .............. 7.8 9.9 7.4 3.0 9.9 10.2 8.0 SaDandy (cream) ................. 7.7 9.6 7.6 7.7 9.1 4.7 7.6 'The commonly grown 'California Blackeye #5' is accepted as the standard for curculio susceptibility. It was used as the yardstick for measuring resistance of other breeding lines and varieties. This does not mean that resistant southernpeas are not damaged by the cowpea curculio, but the damage is signifi- cantly less than than that found in 'California Blackeye #5.' FRUIT AND VEGETABLE RESEARCH REPORT 21 22 ALABAMA AGRICULTURAL EXPERIMENT STATION Is Silver Queen Still the Best-Tasting Sweet Corn? AMY SIMONNE, ERIC SIMONNE, JIM PiTTs, GARY GRAY, AND NANCY GREEN The sweetness, texture, and aroma of sweet corn, along with its high yield and de- sirable grain color, make this a $2.7 million crop in Alabama. For almost 20 years, the most popular sweet corn variety has been the white, "sugary" (su) cultivar 'Silver Queen.' Sweet corn connoisseurs prefer 'Silver Queen' and claim they can identify its typical flavor. However, with the abundance of sugar-en- hanced (se) and supersweet (sh2) white, sweet-corn cultivars, 'Silver Queen' yield and quality may be surpassed. An AAES study was conducted to determine if 'Silver Queen' is actually recognized for its own attributes or if it benefits primarily from "name recogni- tion." A taste-testing panel in this study rated six se and sh2 varieties as superior to 'Silver Queen.' Only a few tasters could properly identify this popular variety. Cooked ears from the sweet corn variety trial conducted at the Chilton Area Horticul- ture Substation in Clanton were served to a panel of tasters. A total of nine varieties were evaluated, but each panelist was asked to rate a selection of only five cultivars. Each five- sample set included 'Silver Queen,' along with four other varieties. Samples were identified only by random three-digit numbers. The panel was comprised mainly of growers, gar- deners, and retirees. Ratings of appearance, sweetness, flavor, and overall preference were significantly af- fected by variety (Table 1). However, most of the selected cultivars received acceptable ratings. The appearance of 'Silverado' and 'Even Sweeter' ears was rated highest, while 'Fantasia' and 'Snow White' were rated low- est. Sweetness was found the highest in 'SS 7801,' 'Treasure,' and 'Even Sweeter.' The sweetness rating of 'Snow White' was the closest to undesirable. Flavor ratings were highest for 'Starshine' and lowest for 'Snow Belle.' 'Treasure' and 'Silverado' received the highest scores for overall preference. Over- all, 'Treasure' was ranked first, 'Even Sweeter' and 'Silverado' tied for second, and MEAN RATINGS OF SELECTED SWEET CORN VARIETIES 1 Variety (seed source) Type 2 Overall Appearance Sweetness Flavor Overall prefere nce rank sum Treasure (Harris Seeds) ................ sh2 9.7 8.5 9.1 8.8 8 Silverado (Harris Seeds) ............... se 9.4 10.4 7.6 8.6 14 Even Sweeter (Asgrow)................ sh2 8.3 10.1 9.0 7.7 14 SS 7801 (Abbott & Cobb) ............ sh2 8.0 7.6 9.9 8.6 15 Fantasia (Asgrow) .......................... se 7.3 7.0 8.0 8.8 21 Starshine (Seneca).......................... se 7.0 7.9 7.4 9.4 22 Silver Queen (Rogers NK) ............ su 7.9 7.3 7.9 7.7 23 Snow Belle (Asgrow) .................... se 7.5 8.2 7.7 6.1 25 Snow White (Harris Seeds).......... sh2 6.0 6.1 5.6 6.3 35 'Varieties were rated on a 0-14 scale (0 = Undesirable/Dislike; 14 = Desirable/Like Extremely). Overall rank sum was calculated by adding the ranks of each attribute (Maximum value = 36); the smaller the overall rank sum, the better. 2 The types of sweet corn are sugary (su), sugar enhanced (se), and supersweet (sh2). Typically, su cultivars have 5-15% sugar at harvest; se, 8-20%; and sh2, 25-40%. 22 ALABAMA AGRICULTURAL EXPERIMENT STATION FRUIT AND VEGETABLE RESEARCH REPORT 23 'SS 7801' was ranked fourth. Three of these four top-rated cultivars are sh2 varieties. 'Sil- ver Queen' was ranked seventh out of nine in overall preference. Panelists were asked to identify 'Silver Queen' among the five corn samples they tasted- Thirty-percent of the panelists prop- erly identified 'Silver Queen,' 58% could not identify it, and 12% did not give any answer. Since each panelist was presented five variet- ies, the odds of correctly choosing 'Silver Queen' at random were 20%. Therefore, only a small fraction of the panel recognized 'Sil- ver Queen.' Panelists also were asked to list all the sweet corn variety names they could remem- ber. Of 67 completed responses, 34% did not name any sweet corn variety. The most com- monly named varieties were 'Silver Queen' (by 61% of the responding panelists), 'Golden Queen' (10%), and 'Bantam' (5%). These re- sults illustrate the popularity of 'Silver Queen.' These results emphasize the importance of cultivar selection in the production of sweet corn. Sugar levels in sweet corn kernels are genetically controlled, thus variety choice is critical. Rankings from this study should be used in conjunction with yield performance and disease resistance before selecting which white sweet corn to plant. Effect of Rate of Banded and Broadcast Phosphorous on Yield of Sweet Corn JOE KEMBLE, ELIZABETH GUERTAL, AND JOHN EASON Broadcast fertilizer application, a method commonly used by sweet corn growers in Ala- bama, can endanger water quality when phos- phorous moves toward surface waters through runoff. However, there is evidence that effi- ciency of P uptake and crop utilization may be increased when P is banded with the crop at planting, compared to broadcast applica- tions. An AAES study was conducted to deter- mine if differences in leaf P concentration and crop yield occurred when P was applied ei- ther as a broadcast or banded treatment. This experiment was conducted at the Sand Moun- tain Substation in Crossville. Preliminary soil tests indicated that the soil was low in available P20 5 . Nitrogen and K 2 0 were applied based on standard crop and soil test recommendations. Phosphorus (0-46-0) was banded (2x2 band) or broadcast at five rates (0, 30, 60, 90, and 120 pounds per acre). 'Snow Belle' sweet corn was sown into plots four rows wide on April 15. Cultural practices followed current recommendations for Ala- bama. Ear leaf samples were removed at pol- lination, dried, ground, and analyzed for phos- phorous content. Treatment differences were apparent in the vegetative growth. Fresh weight of harvested ears did not differ between the banded and broadcast treatments. As level of P increased up to 120 pounds per acre, fresh weight of har- vested ears increased. It appeared that yields were not quite maximized within the range of applied P. However, yield probably would have leveled off near 120 pounds P per acre. Percent of P in corn ear leaves did not dif- fer among treatments. There were no differ- ences in P leaf concentrations between the banded and broadcast treatments, indicating that yield response occurred because of rate of P application as opposed to method. FRUIT AND VEGETABLE RESEARCH REPORT 23 Evaluation of Foliar-applied Insecticides for Control of Whitefringed Beetle in Sweetpotatoes GEOFF ZEHNDER, TERI BRIGGS, AND JIM PrTTS Whitefringed beetles can cause serious dam- age to sweetpotatoes in Alabama and other south- ern states. An AAES study found that soil insec- ticides applied at planting are generally not ef- fective because the insecticide residue dissipates by the time larvae enter the soil. In central and northern Alabama, adult whitefringed beetles emerge from the soil in early July and begin laying eggs. If sufficient mois- ture exists, eggs hatch and larvae, or grubs, crawl into the soil. Larvae develop in the soil and feed on sweetpotato roots. The most serious feeding damage occurs late in the season after larvae have matured. 'Cordner' sweetpotatoes were planted on May 18, 1994, and May 24, 1995, at the Chilton Hor- ticulture Substation in Clanton. Treatments con- sisted of eight rows bordered on both sides by eight untreated rows. Beginning the first week in July, plots were sprayed either weekly or biweekly with a tank mix of Sevin 80S (one pound per acre) plus Penncap-M (one pint per acre). Sprays were applied with a tractor-mounted sprayer deliver- ing 40 gallons per acre. Adults were sampled ap- proximately weekly by examining sweetpotato foliage and the soil surface in four locations per plot. Larvae in the soil were sampled every two to three weeks by taking soil core samples in four locations per plot. Soil samples were taken back to the laboratory where larvae were extracted. Foliage and soil samples taken in 1994 for whitefringed beetles indicated that the foliar in- secticide sprays reduced the numbers of adults and larvae up to fourfold, compared with the un- treated control. Correspondingly, the percentage of damaged sweetpotatoes was reduced 57% in the biweekly insecticide treatment and more than 300% in the weekly insecticide treatment, com- pared with the untreated control. Similar results were seen in the 1995 test, where the weekly and biweekly sprays signifi- cantly reduced whitefringed beetle damage com- pared with the nontreated control. These results indicate that foliar spray treat- ments are an effective alternative to soil-applied insecticides for whitefringed beetle control. INSECTICIDES ON WHITEFRINGED BEETLE POPULATIONS AND DAMAGE IN SWEETPOTATO Treatment Timing Adults Grubs per Percent per plant' soil sample 2 damaged roots 1994 1995 Sevin + methyl parathion 3 ..... . . . . . . . ... Weekly 0.09 0.08 5.1 9.5 Sevin + methyl parathion 3 .... . . . . . . ... Biweekly 0.13 0.13 10.7 4.3 Untreated control........................... -- 0.40 0.42 18.7 25.7 'Adult counts averaged over eight sample dates in July, August, and September. Each time, foliage and the soil surface were examined in four 90-centimeter row sections per plot. 2 Grub counts are from soil core samples from five sample dates in August and September. Cores were 10 cm in diameter and 30 cm deep. 3 Sevin 80S and Penncap-M were applied at one pound and one pint per acre, respectively, using a tractor-mounted sprayer. ,. _if 24 ALABAMA AGRICULTURAL EXPERIMENT STATION I Biocontrol Of Black Rot of Cabbage with Plant Growth Promoting Bacteria: Detection Through Bioluminescence FENNY DANE, GANG WEI, AND JOE SHAW Black rot is considered the most destruc- tive disease of cabbage and other crucifers. In an AAES study, the bacterium which causes black rot was genetically engineered to give off low levels of light, thus making it possible to study the course of this disease I and to test the effectiveness of beneficial S] bacteria in controlling black rot. I Black rot is caused by the bacterium S Xanthomonas campestris pathovar T, campestris (Xcc). Light-producing genes SI from a fish-associated bacterium were intro- SI duced into the Xcc bacteria. These trans- C formed Xcc bacteria could then be detected 1E inside plants with special computer-assisted p1 nc camera equipment long before symptoms were expressed. This technique allowed de- tailed studies of Xcc growth inside plants. Two studies used this method to investigate the effect of different biological control agents on Xcc survival. Greenhouse experiments were set up to test if bacteria that are known to stimu- late the plant's defense mechanism have an ef- fect on growth and survival of the biolumines- cent Xcc. In the first study, cabbage seedlings were in- oculated by syringe injection with one of 10 dif- ferent plant-growth-promoting-root (PGPR) bac- teria. One week later, two leaves per plant were injected with bioluminescent Xcc bacteria. In the second study, mist inoculation experiments were conducted with the three most effective PGPR strains from the first study. Solutions containing the PGPR bacteria were inoculated into the main stems of cabbage seedlings. One week later, the plants were mist inoculated with bioluminescent Xcc bacteria using a hand-held sprayer. Growth of the bioluminescent bacteria was measured over time and quantified with the computer-assisted camera. The ability of the PGPR strains to induce resistance in cabbage was also examined by evalu- ating the protein profiles of leaves of treated and untreated plants. The initial screening study showed that ME1, IN114, and INR7 strains of PGPR bacteria sig- nificantly reduced the growth of Xcc (Table 1). Even though the PGPR effect was more pro- H nounced following the syringe injections in the first study, ME1 treatment in the second study did reduce the spread of Xcc (Table 2). 6 However, no effect was detected on protein )0 profiles of the leaves of treated plants. Also, 0 there was little effect of PGPR on disease 0 symptom reduction. More studies are needed er to determine the long-term effect of PGPR i- bacteria on control of black rot disease in the field environment. TABLE 1. EFFECT OF PGPR STRAINS ON GROWTH OF THE BIOLUMINESCENT BLACK-ROT PATHOGEN IN CABBAGE PLANTS FOLLOWING SYRINGE INJECTION 1 reatment Day 5 Day 8 Day 12 Day 15 Day 20 IE1 .................... 80 7,200 -- -- 13,810 N 114............. 10,260 -- 17,330 -- 0 E76 ................ 3,770 -- 56,860 -- 10,680 4726............. 15,660 34,340 -- 23,670 13,680 NR7 .............. 17,180 36,370 -- 42,480 14,030 E56 .............. 19,870 42,450 -- 24,280 27,040 4 ......................6,380 30,710 -- 56,690 30,820 E34 .............. 15,860 -- 79,450 -- 7,830 E49 .............. 25,380 37,660 -- 25,840 29,160 E52 .............. -- 40,680 47,210 -- 8,090 ontrol .......... 16,910 56,130 -- 87,860 5,200 acterial bioluminescence is expressed as mean light quanta per ant. The lower numbers indicate reduced growth of the biolumi- escent Xcc strain in the plant. TABLE 2. EFFECT OF SELECT PGPR STRAINS ON GROWTI OF THE BIOLUMINESCENT BLACK-ROT PATHOGEN IN CABBAGE PLANTS FOLLOWING MIST INOCULATION Treatment Day 6 Day 11 Day 18 Day 21 Day 2 ME1 ............... 17,750 27,590 56,030 31,080 35,6C INR7 .............. 12,850 14,570 69,590 27,480 23,48 IN114 ............. 23,190 40,340 68,200 56,170 56,39 Control .......... 23,950 27,880 82,990 32,960 32,08 'Bacterial bioluminescence is expressed as mean light quanta p plant. The lower numbers indicate reduced growth of the biolum nescent Xcc strain in the plant. FRUIT AND VEGETABLE RESEARCH REPORT 25 26 ALABAMA AGRICULTURAL EXPERIMENT STATION Evaluation of Fungicide Spray Programs for Brown Rot Control on Peaches ED SIKORA, JIM PiTTs, BOBBY BOOZER, AND ELLEN BAUSKE Peach producers have a variety of products available for use in a fungicide spray program, but effectiveness of disease control, cost per ap- plication, and disease resistance management are vital factors in developing a program. Overuse or abuse of a fungicide can lead to development of fungal strains resistant to that fungicide, as well as all other fungicides within its class. An effective resistance management fungicide spray program relies on reducing the number of applications of a fungicide class dur- ing the season, using tank-mixes of compounds when appropriate, and/or alternating different classes of fungicides within the spray program during the season. Growers who follow these practices will reduce the chances for the devel- opment of a resistant fungal strain in their area. An AAES study was conducted to evaluate the effectiveness of eight fungicide spray pro- grams, using products from various pesticide classes, for the control of brown rot. This dig- ease developed resistance to benzimidazoles (Benlate) in the U.S. and to dicarboximides (Ronilan and Rovral) in Australia. The fungi- cide classes include the DMI's (Orbit, Indar, Nova, and Funginex); the MBC's (Benlate and Topsin M); the dicarboximides (Ronilan and Rovral); and the multi-site compounds (Cap- tan, Bravo, and sulfur). A number of the experimental programs used fewer applications of certain fungicides (Orbit, Indar, Rovral) and/or alternated appli- cations of these fungicides with compounds from other fungicide classes. The experiment was conducted at the Chilton Area Horticulture Substation in Clanton on the cultivar Harvester. Fungicides were applied using an airblast sprayer at a total volume of 100 gallons per acre. ESTIMATED COST OF NINE FUNGICIDE SPRAY PROGRAMS AND THEIR EFFECT ON BROWN ROT CONTROL OF PEACHES Treatment Time of applications' Pct. disease Cost 3 B PF C 2 2 1 D 1 ............................... I 4 I C C I I 1.2 $113.50 2 .................................. C C C C O O 0.0 110.14 3 .................................. C C C C I I 0.0 114.80 4 .................................. C C C C R R 1.2 169.30 5 .................................. C C C C C C 3.8 116.10 6 .................................. C S S S C C 16.8 47.64 7 .................................. C C C R O O 1.2 136.74 8 .................................. C C C R I I 1.2 141.40 Control..................... -- -- -- -- -- -- 26.2 0.00 'Phenological time of spray applications: B = blossom spray (3/20); PF = petal fall (3/29); C = cover sprays (4/12, 4/25, 5/11, 5/29); 2 = two weeks before harvest (6/14); 1 = one week before harvest (6/19); and D = one day before harvest (6/22). 2 There were four cover spray applications for each treatment. 3 Total estimated cost of each spray program. 4 Treatments 1-8 consisted of applications of various combinations of fungicides: 0 = Orbit (four ounces per acre - $9.92 per application); S = sulfur 80% (nine pounds per acre -- $1.49 per application); I = Indar 75WSP (two ounces per acre - $12.25 perapplication); R = Rovral 50WP (two pounds per acre- $39.50 per application); and C = Captan 50WP (six pounds per acre - $12.90 per application). No fungicides were used in the control, thus no costs were incurred. 26 ALABAMA AGRICULTURAL EXPERIMENT STATION FRUIT AND VEGETABLE RESEARCH REPORT 27 Treatments were applied at full bloom, petal fall, as cover sprays, and at preharvest. Fruit were harvested on June 23. Fruit samples from each treatment were rated for percent brown rot five days after harvest following incubation at room temperature. . The weather conditions in 1995 were un- usually hot and dry for the area. Little or no brown rot was observed in the orchard before harvest. Differences were observed among treatments for brown rot following the five-day incubation period. Significantly more brown rot occurred in the unsprayed control treatment and the sulfur/Captan spray program than in the other seven treatments. There were no differ- ences and little disease observed among the other seven treatments. Estimate costs of each spray program is shown in the table. Evaluation of Fungicides for Brown Rot and Scab Control on Peaches ED SIKORA, JIM PTTS, AND ELLEN BAUSKE Brown rot, scab, and Rhizopus rot are three diseases that limit production of peaches each year in Alabama. In 1995, an AAES experiment was conducted to evaluate a new experimental fungicide product developed by Zeneca for con- trol of these diseases. The new product, known as 5504, was com- pared to two rates of Captan for full-season use (except preharvest sprays). The experiment was conducted at the Chilton Area Horticulture Sub- station in Clanton, using the cultivar Alred Elberta. Fungicides were applied using an airblast sprayer at a total volume of 100 gallons per acre. Treatments were applied at first pink (March 19), full bloom Tr (March 22), shuck split (March 31) and in cover sprays (April 14 and 25, May 11 Co and 29, June 13 and 30). The fungicide 55 Orbit EC (four ounces per acre) was ap- Lal 55( plied as a preharvest spray for all treat- La ments except the control on July 13. Fruit 55( were harvested on July 14 and rated for La Ca percent scab incidence. After five days of Ca incubation at room temperature, fruit were 'R; rated for percent brown rot and Rhizopus 2 TI rot. wi The weather conditions in 1995 were un- usually hot and dry for the area. Little brown rot and Rhizopus rot were observed in the or- chard before harvest, nor were there any sig- nificant differences among treatments five days after harvest. The intermediate and high rate of 5504, along with the six-pound rate of Captan, provided the best control of scab. The low rate of 5504 was significantly better then the con- trol but did not perform as well as the interme- diate and high rates. EFFECT OF FUNGICIDES ON SCAB AND BROWN ROT CONTROL ON PEACHES eatments Scab Brown Rot Rhizopus pct. pet. pct. ntrol 2 ............. . ... .... .... . . . . . ........ 84.3 7.5 3.1 04 80WG (0.05 lb. ai) + tron 1956 (1 pt.)...................... 35.0 1.2 0.0 04 80WG (0.10 lb. ai) + tron 1956 (1 pt.)...................... 11.8 0.0 1.2 04 80WG (0.15 lb. ai) + tron 1956 (1 pt.) ...................... 13.7 1.2 0.6 ptan 50WP (6lb.).........11.8 1.8 1.2 ptan 50 WP (4 lb.) .................. 26.2 0.0 1.8 ates per acre of the respective treatments are in parentheses. he control received no fungicide applications but was treated th insecticide. FRUIT AND VEGETABLE RESEARCH REPORT 27 Evaluation of Mechanical Thinners on Bloom/Fruit Removal and Yield of Encore Peaches BOBBY BOOZER, BILL DOZIER, AND JIM Prrs Proper fruit thinning is necessary in peach pro- duction to obtain marketable size fruit. Most peaches are thinned by hand, which is costly and labor in- tensive. Mechanical shakers, which are used in some heavy fruiting years, can thin fruit but are not al- ways consistent in performance. Recently, a me- chanical rope thinner was introduced to growers for thinning during bloom. AAES researchers at the Chilton Area Horticul- ture Substation (CAHS) evaluated the bloom thin- ning ability of the peach rope thinner in a grower block of Encore peaches. The mechanical rope thin- ning equipment consisted of a rotating cross beam, 10 feet in length, with 12-foot ropes doubled and spaced five inches apart along the beam. This equip- ment was mounted on a front-end loader. Objectives were to determine the percent of blooms removed, where bloom removal was occurring within the fruit- ing canopy, and how mechanical rope thinning com- pared with mechanical shaking on yield and size of fruit. Because of the versatility of the peach rope thin- ner, three different operation methods were used: single pass, double pass, and bi-directional double pass. All operations were performed at the same rate of speed. These methods were compared to the me- chanical shaker, which was operated based on guide- lines used by the CAHS. Results showed that the mechanical rope thin- ner can remove an average of 42% of the blooms when operated at 2 mph and 1.5 revolutions per tree with a single clockwise pass. Using the same trac- tor speed and speed of rotation, the mechanical rope thinner removed 55% of the blooms with two clock- wise passes. Making two passes - one clockwise, one counter-clockwise - produced 57% bloom re- moval. All three rope thinning methods removed more blooms from above five feet of the fruiting canopy. Also, the single pass and double pass meth- ods removed slightly more blooms on the right side of scaffold limbs. The mechanical shaker, which was used 30 days after full bloom, removed 73% of the fruit; a higher percent of the fruit was removed from below five feet within the fruiting canopy. There was a strong trend toward increasing to- tal yield by use of the mechanical rope thinner, com- pared to the mechanical shaker (see table). Fruit weight increased after the double-pass, rope thin- ner operations. However, extremely dry weather during the growing season is believed to have re- duced overall treatment effects. The Mechanical Rope Peach Thinner appears to be a viable option for peach producers to use for removing excess fruit during the bloom stage. Be- ing able to alter the number of passes, speed of trac- tor and rotation rate of ropes gives producers op- tions to how much thinning they want to accom- plish. Blooms can easily be counted from five to ten shoots positioned five feet or higher within the fruiting canopy and recounted after rope thinning operation is performed. Average bloom removal can be calculated and adjustments can be made to thin- ning. Touch up hand thinning will still be required, but more of the touch up work will be closer to the ground, which should reduce the time needed to perform the task. PERCENT, NUMBER, AND POSITION OF BLOOMS/FRUIT REMOVED BY FOUR THINNING TREATMENTS Treatment Perc6nt removed Number removed Total Average per shoot by position on tree yield Fruit weight Left Right High Low pct. no. no. no. no. lb. oz. M echanical Shaker ........................................................ 72 18 17 15 20 101.43 4.73 Mechanical Rope Thinner Two-pass, clockwise and counter-clockwise............57 15 15 17 13 119.07 5.08 Two-pass, clockwise only ............................................ 55 12 15 15 12 116.87 5.02 One-pass .................................................. 42 9 13 11 10 114.66 4.44 28 ALABAMA AGRICULTURAL EXPERIMENT STATION