Vegetable Report 2000
ABOUT THIS COLLECTION
The Vegetable Report is one of several commodity-based agricultural research reports published by the University of Arizona.
This report was first published in 1965.
The purpose of the report is to provide an annual research update to farmers, researchers, and those in the agricultural industry. The research is conducted by University of Arizona and USDA-ARS scientists.
Both historical and current Vegetable Reports have been made available via the UA Campus Repository, as part of a collaboration between the College of Agriculture and Life Sciences and the University Libraries.
Contents for Vegetable Report 2000Insects
- Alternative IPM Programs for Management of Lepidopterous Larvae in Fall Lettuce
- Aphid Control in Cabbage Study
- Baseline Susceptibility of Cabbage Looper to Insecticides
- Comparison of Neonicotinoid Use Patterns for Silverleaf Whitefly Management in Melons and Broccoli
- Evaluation of Foliar Insecticides for Whitefly Control in Cantaloupes
- Impact and Management of Western Flower Thrips on Romaine Lettuce
- Management of Western Flower Thrips in Head Lettuce with Conventional and Botanical Insecticides
- New Chemistry and Pyrethroid Combinations for Lepidopterous Pest Control in Broccoli
- New Insecticides for Diamondback Moth Control in Cabbage
- Population Dynamics and Distribution of Aphid Species on Head Lettuce in the Yuma Valley
- Predicting Dispersal by Whitefly Parasitoids
- Pro-active Management of Beet Armyworm (Spodoptera exigua) Resistance to IGRs, Tebufenozide and Methoxyfenozide
- Seasonal Abundance and Control of the Lettuce Aphid, Nasonovia ribisnigri, on Head Lettuce in Arizona
- Susceptibility of Arizona Whiteflies to Neonicotinoid Insecticides and IGRs: New Developments in the 1999 Season
- Comparative Effect of Five Fungicides on the Development of Root and Stem Rot and Survival of Chile Pepper Plants Grown in Field Soil Naturally Infested with Phytophthora capsici
- Comparison of New Fungicides to Manage Sclerotinia Leaf Drop of Lettuce in 2000
- Effect of Cultivar and Actigard on Development of Powdery Mildew on Lettuce
- Effect of Preplant Fumigation on Yield of Chile Pepper Infected with Root-Knot Nematode
- Evaluation of Fungicide Performance for Control of Powdery Mildew on Lettuce in 2000
- Performance of New Chemistries for Control of Powdery Mildew of Cantaloupe in 1999
- Fall Planted, Late Maturing Onion Variety Trial
- Field Evaluation of Broccoli Varieties Grown in Southwest Low Desert Soils
- Field Evaluation of Cauliflower Varieties Grown in Southwest Low Desert Soils
- Field Evaluation of Crisp-head Lettuce Varieties Grown in Southwest Low Desert Soils
- Lettuce Variety Trial
- Melon Variety Trial
- Squash Variety Trial
- Sweet Corn Variety Trial
Screening New Herbicides for Weed Control in Head and Leaf Lettuces and BroccoliIn preemergence (PREE) herbicide testing, all three lettuces, head, romaine, and red leaf, exhibited some tolerance to carfentrazone, sulfentrazone, flumetsulam, rimsulfuron, and thifensulfuron while giving effective weed control. In postemergence (POST) testing, cloransulam and flumetsulam controlled weeds at the lowest applied rates while lettuces were safe to cloransulam at 0.01 lb AI/A and flumetsulam at 0.03 lb AI/A. Imazamox was safe on lettuces at 0.01 lb AI/A and controlled weeds at 0.007 lb AI/A. For broccoli, sulfentrazone, fluroxypyr, and thifensulfuron applied PREE demonstrated reasonable safety and weed control. Cloransulam, flumetsulam, and fluroxypyr applied POST on broccoli exhibited adequate crop safety and good weed control.
Herbicide Screen for MelonsSeventeen herbicides recently gaining registrations in corn, soybeans, or other major crops were evaluated in screening tests for potential use in melons. In a preemergence herbicide screening test, flumioxazin, dimethenamid, halosulfuron, and s-metolachlor demonstrated melon crop safety at rates higher than rates for effective weed control. In a postemergence screening test, halosulfuron and rimsulfuron gave acceptable weed control with adequate crop safety. Flumetsulam and thifensulfuron appeared to offer some acceptable weed control with a very narrow margin of crop safety. Herbicides that did not offer adequate melon crop safety or acceptable weed control in the screening tests were carfentrazone, sulfentrazone, cloransulam, flumiclorac, fluthiamide/metribuzin, imazamox, isoxaflutole, triflusulfuron, primisulfuron/prosulfuron, and clomazone.
Halosulfuron for Weed Control in WatermelonHalosulfuron at rates ranging from 0.05 to 0.10 lb AI/A with no adjuvant added to the POST application spray did not cause any injury to watermelons. Halosulfuron did not appear to cause significant crop injury earlier in the season to reduce marketable fruit yield at harvest. Halosulfuron was highly effective against London rocket but did not control purslane or groundcherry. Weed control efficacy was improved significantly when Latron CS-7 or Activator-90 was added to halosulfuron at either 0.05 or 0.075 lb AI/A. LI-700 did not improve the activity of halosulfuron over the treatments without an adjuvant.
Evaluation of Herbicides for Nutsedge Control in CarrotsHalosulfuron and sulfentrazone were not safe to carrots at the lowest rates tested at 0.025 and 0.188 lb AI/A, respectively. At 20 DAT, halosulfuron at 0.038 to 0.075 lb AI/A gave better than 92% control of nutsedge in carrots. Nutsedge control was 77 to 80% at 20 DAT sulfentrazone applied at 0.188 to 0.375 lb AI/A. Both herbicides demonstrated slow activity against nutsedge during the first 7 DAT and then progressed to reduce weed growth at 13 to 20 DAT. Sulfentrazone appeared to act slightly faster than halosulfuron but showed maximum activity at 13 to 20 DAT.
Sweet Corn Variety TrialSixteen sweet corn varieties were grown in replicated small plot trials with two dates of planting at the Safford Agricultural Center in 1999. Candy Corner ranked number one and two in the early and late dates of planting, respectively, and FMX 413 ranked number one in the later date of planting study. Both varieties produced over 2,500 dozen ears per acre. Sugar readings were made and tabulated for all varieties using a portable refractometer.
Squash Variety TrialFive Zucchini varieties and four yellow crook/straight-necked squash were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Varieties were picked regularly during the growing season. Yields are shown in tabular form and also graphically to indicate how each variety performed throughout the season.
Melon Variety TrialSeven cantaloupe varieties and two Honeydew melon varieties were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Varieties were picked regularly during the growing season. Yields are shown in tabular form to indicate how each variety performed during the season.
Lettuce Variety TrialEleven head lettuce varieties and four leaf lettuce varieties were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Desertgreen variety of head lettuce from Harris Moran produced a crop with the best head weight, size and firmness rating. Premiere variety followed closely behind. Of the leaf lettuce varieties tested, Saguaro Romaine produced the best quality and quantity product. Per acre yields are calculated for each variety in the study.
Field Evaluation of Crisp-head Lettuce Varieties Grown in Southwest Low Desert SoilsCrisp-head lettuce plays an important role in Yuma’s economy. An estimated 51000 acres are cropped to large number of varieties each year with planting season that spreads from late August to March. Three demonstration sites and three planting dates were selected to compare new and existing varieties of head lettuce on growers’ fields using standard farming practices. Selected growth parameters were evaluated throughout the growing season. Results indicate that varieties tested at JV Farms in Welton and at Yuma Agricultural Center (YAC) are expected to do well if grown under similar conditions and planting time. Some varieties tested during the second planting slot on Doug Melon Farm experienced some incidence of diseases. All three planting sites showed a significant head weight difference and two out of three planting sites showed a significant head diameter difference.
Field Evaluation of Cauliflower Varieties Grown in Southwest Low Desert SoilsSelection of adapted varieties to environmental factors and soil types are paramount to growing profitable cauliflower crops. Varieties are selected for uniform maturity, field holding capability, head size, shape and color. The objective of this demonstration trial is to evaluate new and existing commercial varieties under standard field conditions. Seven varieties were planted in a single row and evaluated at Yuma Agricultural Research Center (YAC) for their agronomic characteristics and their commercial values. All varieties tested performed well with an overall rating of 4 or better, indicating that when planted under similar conditions and planting dates, these varieties are expected to do well. However a significant head weight and head diameter difference was observed among varieties tested.
Field Evaluation of Broccoli Varieties Grown in Southwest Low Desert SoilsBased on acreage, broccoli is the third largest vegetable crop in Yuma County, after head lettuce, and romaine. It generates over $36 000000 a year. Efforts are continuously made by both seed industry and growers to grow better varieties that respond to consumers’ choice. Selection of newly adapted varieties is made based on agronomic performance as well as commercial value. Stand uniformity, disease resistance, color, head shape, and head size are among characteristics that are evaluated. The objective of this demonstration trial is to evaluate the characteristics of new varieties grown under standard cultural practices. Twelve varieties were tested at Yuma Agricultural Research Center. No incidence of disease was observed and the overall evaluation rating was greater than 4 indicating that all varieties tested will do well under similar growing conditions and planting date. Significant head diameter and plant height were observed among varieties tested.
Fall Planted, Late Maturing Onion Variety TrialThirteen late maturing onion varieties were planted in the fall of 1998 and grown in a replicated small plot trial on the Safford Agricultural Center. Bulbs were pulled and the tops removed in early June. Three NuMex varieties, Mesa, Starlite and BR1, produced the best yields. Yields are shown in tabular form together with size distribution and quality characteristics.
Performance of New Chemistries for Control of Powdery Mildew of Cantaloupe in 1999Powdery mildew on melons is an annual disease problem in Arizona. Sphaerotheca fuliginea is the plant pathogenic fungus that causes powdery mildew of cucurbits, which include cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant levels. Factors that favor development of powdery mildew on melons include moderate temperatures and relative humidity, succulent plant growth, and reduced light intensity brought about by a dense plant canopy. Potential new fungicides were evaluated and compared to existing chemicals for control of powdery mildew of cantaloupe in a field trial conducted during the spring of 1999 at the Yuma Agricultural Center. A high level of disease had developed by crop maturity (June 29). On nontreated plants 43% of the upper leaf surface was covered by powdery mildew, whereas the level on the underside of leaves was 78%.. All of the 34 different treatments significantly reduced the level of powdery mildew on both sides of leaves, compared to nontreated plants. The best treatments among those tested with respect to disease control on the underside of leaves, where disease control is more difficult than on the tops of leaves, included Topsin+Trilogy, Benlate, Benlate+Trilogy, Quadris, A815, Topsin+Microthiol, and Topsin. The potential availability of new chemistries for management of powdery mildew of cantaloupe and other cucurbits could help improve overall control of powdery mildew as well as the implementation of fungicide resistance management strategies, which strive to minimize the risk of resistance development by the pathogen to these compounds.
Evaluation of Fungicide Performance for Control of Powdery Mildew on Lettuce in 2000Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2000. Powdery mildew appeared in our plots by Feb 9 and reached high levels by plant maturity on Mar 2. Nontreated lettuce plants were heavily infected with powdery mildew at plant maturity, whereas the disease ranged from low to virtually nonexistent levels in plots treated with BAS 500, Quadris+Actigard, Flint, Flint+Actigard, Flint alternated (alt.) with Trilogy, Rally, Microthiol, EksPunge alt. with Microthiol, KHHUBF-99-001, Quinoxyfen, Flint alt.with Serenade, Rally alt. with Serenade, and Serenade alt. with Microthiol. These compounds have various modes of action, and some could be available for “organic” production. The future availability of one or more of these chemistries under development could help in efforts to control powdery mildew of lettuce and to establish and maintain a fungicide resistance management program for plant disease control products of importance for this crop.
Effect of Preplant Fumigation on Yield of Chile Pepper Infected with Root-Knot NematodeA field test was established in 1999 to determine the effect of preplant soil fumigation on yield of chile pepper in southeastern Arizona in order to give growers data on which to base management decisions. Replicated plots within a nematode-infested field planted with New Mex 6-4 chile in March 1999 were either treated with Telone II fumigant at 7 gal/A two weeks before planting or not treated. In a mid-season assay in July 1999, the effects of fumigation were evident in plant canopy growth although numbers of J2/cc soil were not significant between treatments (p=0.058). Differences in yields between fumigated plots and untreated plots were significant (p=0.014). The average yield in fumigated plots was 12.4% higher than that in untreated plots.
Effect of Cultivar and Actigard on Development of Powdery Mildew on LettuceNine different cultivars of lettuce were planted at the Yuma Valley Agricultural Center. Plants were treated four times with two different rates of Actigard. Control plants were not treated. Near plant maturity (Mar. 23, 2000) the severity of powdery mildew was recorded. Among nontreated plants, Cibola, Conquistador, and Coolguard had the lowest levels of powdery mildew. On the other hand, Bos 9003 and Mohawk had significantly higher levels of powdery mildew than all other tested cultivars. Four applications of Actigard at a rate of 14 g. of active ingredient per acre significantly reduced the level of powdery mildew on all nine tested cultivars of lettuce. On two lettuce cultivars, powdery mildew was significantly lower when treated with Actigard at the 28 g. a.i./A rate when compared to the 14 g. a.i./A rate. No evidence of phytotoxicity was apparent on plants treated with Actigard. This study suggests that lettuce cultivars differ in susceptibility to powdery mildew. Also, Actigard was able to provide added protection against powdery mildew for all tested lettuce cultivars.
Comparison of New Fungicides to Manage Sclerotinia Leaf Drop of Lettuce in 2000Sclerotinia minor and S. sclerotiorum are the two soil-borne pathogenic fungi that cause Sclerotinia leaf drop in Arizona. Moist soils and moderate temperature favor this disease. Some new fungicides in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 1999-2000. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. In this trial, the final count of dead lettuce plants usually was numerically reduced, compared to nontreated plots, in plots infested with either pathogen that were treated with the standard compounds Ronilan or Rovral as well as the experimental compound Medallion; however, the reduction was significant only in plots infested with Sclerotinia sclerotiorum. The number of dead plants in plots infested with either Sclerotinia minor or S. sclerotiorum was significantly reduced by another experimental chemistry, Fluazinam. Finally, a biological control product, Serenade, significantly reduced disease in plots containing S. minor, but not S. sclerotiorum. Continued demonstration of efficacy by Serenade may provide the opportunity to utilize a biological control product to reduce the incidence of Sclerotinia leaf drop of lettuce caused by S. minor.
Comparative Effect of Five Fungicides on the Development of Root and Stem Rot and Survival of Chile Pepper Plants Grown in Field Soil Naturally Infested with Phytophthora capsiciFive different fungicides, including azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and mefenozem (metalaxyl), were evaluated for their ability to inhibit the development of root and crown rot and increase the survival of chile pepper plants grown in soil naturally infested with Phytophthora capsici. For chile pepper plants grown in field soil naturally infested with P. capsici and subjected to a 48 h flood period every 2 weeks, growth and survival of plants receiving one treatment of dimethomorph at 100 μg/ml or fluazinam at 1,000 μg/ml were significantly greater than that for plants treated once with azoxystrobin at 1,000 μg/ml or fosetyl-Al at 3,000 μg/ml. For each tested fungicide, values for duration of plant survival and shoot and root fresh weight usually were numerically larger but not significantly different for chile peppers receiving water as needed compared to those flooded for 48 h every 2 weeks. The potential and relative value of azoxystrobin, dimethomorph, fosetyl-Al, and fluazinam as chemical management tools for Phytophthora root and stem rot on chile pepper, in addition to mefenozem (metalaxyl), has been demonstrated.
Susceptibility of Arizona Whiteflies to Neonicotinoid Insecticides and IGRs: New Developments in the 1999 SeasonWhiteflies are serious pests of cotton, melons, and winter vegetables in Arizona’s low deserts. Successful management of whiteflies requires an integrated approach, a critical element of which is routine pest monitoring. In this paper we report findings of our 1999 investigations of resistance of Arizona whiteflies to insect growth regulators (IGRs) and neonicotinoid insecticides. Whiteflies collected from cotton fields, melon fields and greenhouses were tested for susceptibility to imidacloprid (Admire /Provado), and two other neonicotinoid insecticides, acetamiprid and thiamethoxam, and to two insect growth regulators (IGRs), buprofezin (Applaud ) and pyriproxyfen (Knack ). Contrasts of 1999 and 1998 results indicated increased susceptibilities, on average, to both imidacloprid and buprofezin of whiteflies collected from cotton. A cropping system study showed that whiteflies collected from spring melons had significantly lower susceptibility to imidacloprid than those collected from cotton or fall melons. The opposite was found for pyriproxyfen, to which whiteflies from cotton and fall melons had lower susceptibility than those from spring melons. As in 1998, whiteflies with reduced susceptibility to imidacloprid continue to be found in certain locations, particularly in spring melon fields and greenhouses. Results of our laboratory bioassays on susceptibility of Arizona whiteflies to neonicotinoid insecticides provided evidence of a low order cross-resistance between imidacloprid, acetamiprid and thiamethoxam. Monitoring in 1999 provided the first evidence of reduced susceptibility of Arizona whiteflies to pyriproxyfen.
Seasonal Abundance and Control of the Lettuce Aphid, Nasonovia ribisnigri, on Head Lettuce in ArizonaSmall plot studies were conducted in 1999/2000 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. Seven, 0.25 acre planting of head lettuce were established beginning in October with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a sidedress application of Platinum post-planting or allowed to remained untreated. Lettuce aphids were first detected in our experimental area on Feb 14 in PD 3 in untreated plants. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 °F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90 °F. We were surprised by the marginal level of lettuce aphid control provided by the systemic insecticides. Lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. In the later planting dates, both Admire and Platinum contained significantly fewer aphids and infested plants than the untreated control. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. We are hesitant to draw conclusions from our results collected from a single season , and plan to replicate this work next year under different environmental conditions and higher rates of Admire and Platinum.