Vegetable Report 1992
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 1992
- Broccoli Variety Trials 1990/1991
- Broccoli Downy Mildew Tolerance Trial, 1990/1991
- Rate by Timing Interactions of Propel on Head Lettuce
- 1991 Virus Survey of Cantaloupe in Yuma
- Cauliflower Variety Trials 1990/1991
- Cantaloupe Variety Trial, 1991
- UA Seedless Watermelton Cultivar Trial - 1991
- Watermelon Response to Soluable and Slow Release Nitrogen Fertilizers
- Nitrogen Management in Drip Irrigated Leaf Lettuce, Spinach and Green Crops
- Optimizing Nitrogen and Water Inputs for Trickle Irrigated Watermelons
- Fungicides Evaluated for Control of Sclerotinia Leaf Drop of Lettuce in 1991 Field Test
- Fungicides Evaluated for Control of Powdery Mildew of Cantaloupe in 1991 Field Trial
- Fungicides Evaluated for Control of Rhizoctonia Bottom Rot of Lettuce in 1991 Field Trials
- A Pilot Project to Evaluate the Use of Geographic Information Systems (GIS) to Analyze Regional Data on Pests and Diseases of Vegetables
- A Critical Examination of Flight by the Sweet Potato Whitefly
- Evaluation of Imidacloprid (NTN 33893) for Control of Aphids on Broccoli
- Comparative Effectiveness of Bacillus thuringiensis Formulations Against Lepidopterous Pests of Fall Lettuce
- Effects of Insecticides on Leafminers, Liriomyza spp., and Associated Parasitoids on Spring Cantaloupes
- Effect of Oils and an Insecticide Applies to Snap Beans on Leafminer and Associated Parasitoid Numbers
- Effect of Insecticides on Sweetpotato Whitefly Numbers and Growth of Broccoli
- Effects of Lettuce Insecticides Applied at Planting
- Effect of Oil Treatments on Head Lettuce Photosynthesis and Growth
- Evaluation of Two Electrostatic Sprayers Compared with Conventional Application Methods for Control of Insects in Spring Head Lettuce
- Effectiveness of Oils in Water for Leafminer Control in Fall Head Lettuce
- Control of Thrips in Seed Onions and Resultant Seed Yields
- Evaluation of Agri-Mek with Various Oils and Adjuvents for Control of Leafminers in Spring Head Lettuce
- Evaluation of Oils and Insecticides for Leafminer Control in La Paz County Snap Beans
- Comparison of Capture, Capture and Thiodan, Malathion and Pounce Insecticides for Control of Two Aphid Species on Broccoli Seed
- Evaluation of Oils, Insecticides and Insect Growth Regulators for Control of Sweetpotato Whitefly on Muskmelon and Watermelon
- Evaluation of Insecticides for Control of the Apache Cicada on Asparagus
- Experimental Use of Beescent® to Influence Honey Bee Visitation to Watermelon
- Dry Matter Partitioning of Cowpea (Vigna Unguiculata (L.) Walp.) Under Water Deficit Conditions
Dry Matter Partitioning of Cowpea (Vigna Unguiculata (L.) Walp.) Under Water Deficit ConditionsWater Stress caused reduction of seed yield in cowpea plants by decreasing total biomass and photosynthesis. The source leaf, pod and seed water potential of stressed cowpea were lower than water potential in non-stressed plants. No differences in water potential and turgor were observed between pod walls and seed of cowpea plants. Partitioning of the total above ground dry matter was similar for both stressed and nonstressed cowpea plants. Photosynthetic rates of single leaves from cowpea were greater for nonstressed than stressed plants. The duration of seed growth of cowpea was not different between stressed and nonstressed plants; however, rate of seed growth at the end of seed filling period was greater in nonstressed plants. Seed growth rate of both stressed and nonstressed cowpea plants declined at about the same time photosynthesis of the source leaf declined. Leaf area index was greatest in nonstressed cowpea.
Experimental Use of Beescent® to Influence Honey Bee Visitation to WatermelonA commercial product called Beescent® containing a mixture of chemicals including chemicals used by honey bees as pheromones, was applied to watermelons in early bloom on Aug. 15, 1991. Honey bee visitation to treated, 18-row plots, were significantly higher than to untreated for only 2 days, the day of treatment and the next day. Watermelon yields were not effected. The daily high temperatures reached 86-88 °F, so that most of the chemical had volatilized away by the end of the first day.
Evaluation of Insecticides for Control of the Apache Cicada on AsparagusFive insecticides were evaluated for Apache cicada control in asparagus. Best control was achieved by two unregistered pyrethroid insecticides. The currently registered pyrethroid insecticide in this study (Pounce) was not as effective as Capture or Baythroid. Methomyl Pinnate) applied after the experiment was also very effective in controlling adult Apache cicadas. Di-Syston provided very little control.
Evaluation of Oils, Insecticides and Insect Growth Regulators for Control of Sweetpotato Whitefly on Muskmelon and WatermelonFive insecticides, four oils, one soap, and two insect growth regulators were evaluated for control of sweetpotato whitefly on muskmelons and watermelons in 1990. Best control (> 80%) was noted from the insect growth regulators at 11 days post treatment, but declined thereafter. Oils as a class provided some control but not all oils provided similar results. Insecticides tested did not provide adequate control and resulted in increased whitefly egg and nymph numbers at 11 days post treatment.
Control of Thrips in Seed Onions and Resultant Seed YieldsFour insecticides were evaluated for their effect on onion seed production in Yuma County where two species on thrips (western flower and onion) were present in seed fields. Visual differences between treatments resultant from onion thrips damage was evident within 10 days after treatments were applied at flower opening. Lorsban, Ammo and Capture treatments provided control of onion thrips based on condition of seed heads. Only Ammo and Capture treatments increased seed yield as the Lorsban treatment was thought to repel bees which are needed for pollination. Pyrethroid treatments yielded 40% more than the untreated check. Damage from onion thrips to onion seed in Yuma County is conservatively calculated to currently be at least $1.1 million annually.
Effect of Insecticides on Sweetpotato Whitefly Numbers and Growth of BroccoliEleven treatments were applied for sweetpotato whitefly B- biotype control. Best control (62.4%) was evidenced by the Ambush + Thiodan treatment, which had fewest nymph numbers 8 days post treatment and had larger plant sizes (46.3%) 14 days post treatment than the untreated check. Plants in plots receiving treatments including Thiodan and/or Lorsban were also at least 20% larger than the untreated check. Fewest number of adult whiteflies two days post treatments were noted in the Thiodan + M-Pede treatment. Certain treatments increased whitefly numbers.
Effects of Insecticides on Leafminers, Liriomyza spp., and Associated Parasitoids on Spring CantaloupesA study was conducted to determine the effects of repeated insecticide applications on leaf niner and parasitoid populations on spring melons. After four applications, none of the insecticides induced large build-ups of leafminer larvae. A new material, AC 303630, was very effective in maintaining low numbers of pupae. However, the results of this preliminary test indicate that all insecticides tested had a negative impact on the parasitoid population. In general, in the absence of insectcides, parasitoids were capable of maintaining L. sativae populations at low levels in the experimental plots.
Comparative Effectiveness of Bacillus thuringiensis Formulations Against Lepidopterous Pests of Fall LettuceA field study was conducted at Yuma in 1991 to examine the relative effectiveness of several formulations of Bacillus thuringiensis on beet armyworm and cabbage looper on seedling and pre-cupping lettuce. Several applications were made before and after thinning. Results of the study suggest that most formulations are capable of controlling small larvae. However, because of the inherent variation in beet armyworm dispersion, it was difficult to statistically attribute differences in pest levels due to insecticide efficacy.
Evaluation of Imidacloprid (NTN 33893) for Control of Aphids on BroccoliThe new insecticide Imidacloprid (NTN 33893), which is currently being developed for use on vegetable crops, was evaluated on broccoli for control of aphid species. Studies conducted in the spring of 1991 showed that this material applied postemergence as a granular formulation was extremely effective in preventing aphid colonization throughout the season. Aphid control and broccoli yields were significantly greater in plots treated with Imidacloprid. Due to low numbers of aphids in 1992, we were unable to detect differences in aphid numbers between Imidacloprid treatments and the untreated control.
A Critical Examination of Flight by the Sweet Potato WhiteflyIn the past we have assumed that sweet potato whiteflies, Bemisia tabaci (Gennadius), were poor fliers with a limited ability to disperse. This assumption was based on the fact that sweet potato whiteflies are extremely small insects (24 -44 μg) and consequently would be subject to desiccation. We also thought small size would limit their capacity to store sufficient energy reserves to sustain flight for long periods of time. Recent experiments have indicated we were wrong on several counts. Data collected in the laboratory using a vertical flight chamber have revealed a number of interesting facts. Of importance is the fact that a portion of the population is capable of sustaining flight for more than 2.5 hours. In a wind-aided situation, this means they can be moved more than 25 miles in a 10 mph wind. Other details of flight behavior are being made clear to us. For example, we found that flight activity is influenced by host plant quality and age of the whitefly. We hope to eventually be able to predict when whiteflies are going to migrate between crops. This will allow growers to make informed decisions concerning planting dates. We are also working in the field to confirm laboratory results.
A Pilot Project to Evaluate the Use of Geographic Information Systems (GIS) to Analyze Regional Data on Pests and Diseases of VegetablesGeographic Information Systems (GIS) are computer databases that organize information in a spatial framework. This allows the analysis of data based in part on location. A pilot project has been set up in the Yuma Valley to explore the use of GIS to study the influence of crop sequences, weeds, urban areas, and insect vector populations on the incidence of virus diseases of vegetables. The goal is to learn to collect field observations in such a way that long term regional trends can be understood and visualized. Such information can then be used in management plans.
Fungicides Evaluated for Control of Rhizoctonia Bottom Rot of Lettuce in 1991 Field TrialsBottom rot of lettuce, caused by the soil -borne fungus Rhizoctonia solani, can cause economic losses on early season lettuce harvested in November. First evidence of the disease is the appearance of brown, sunken, necrotic areas on the midribs of leaves touching the soil. Under favorable environmental conditions, the pathogen grows from leaf to leaf inside the head. If the fungus invades the leaves of the marketable head it and all similarly infected heads are left in the field resulting in economic losses. Field trials were established to evaluate the potential level of disease control obtainable by applying Ronilan or Rovral to lettuce beds immediately after thinning. No significant reduction in loss of marketable heads was observed in these trials, although there was a trend toward lower levels of bottom rot when either fungicide was in place.