Vegetable Report 1991
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 1991
- Broccoli Variety Trials, 1989/1990
- Cantaloupe Variety Trial, 1990
- Cauliflower Variety Trials, 1989/1990
- Watermelon Variety Trial, 1990
- International Asparagus Cultivar Trial
- Sustainable Lettuce Production
- Stand Establishment of Lettuce Seed Produced in Different Seasons
- Harvest Season Effects on Asparagus Yield
- Effect of Nitrification Inhibitors on Nitrogen Utilization Efficiency in Sweet Corn
- Nitrogen Utilization Efficiency in Melons Using Soluble and Slow Release Fertilizers
- Nitrogen and Water Effects on Yield, Quality and Tissue Nitrate Concentration in Subsurface Trickle Irrigated Melons
- Cultural Alternative for Avoidance of Lettuce Infectious Yellows Virus (LIYV)
- Biological Characteristics and Esterase Patterns for Bemisia tabaci Populations, and the Association of Silverleaf Symptom Development in Squash with One Population
- Potential New Fungicides for Control of Powdery Mildew of Cantaloupe - 1990 Evaluation
- Effect of Sunstainable Versus Conventional Fertilization Practices on Populations of Pythium and Fusarium on Roots of Lettuce in 1990 Field Test
- Comparison of Different Fungicides for Control of Downy Mildew of Broccoli -- 1991 Field Trial
- Effect of Fungicides Applied at Different Rates on Control of Sclerotinia Leaf Drop of Lettuce -- 1990 Field Test
- Broccoli Downy Mildew Tolerance Trials
- Evaluation of Biological Insecticides for Control of Beet Armyworm in Lettuce
- Effectiveness of Pesticides with Novel Chemistries Against Different Life Stages of the Sweet Potato Whitefly
- Poast/Lettuce Trial
- Kerb/Lettuce Variety Trial, 1989/1990
- Water Stress-Induced Osmotic Adjustment in Expanding Leaves of Tepary Bean )Phaseolus actifolins, Gray) Seedlings
- Canola Growth Reponse to Different Rates of Irrigation Regimes
Water Stress-Induced Osmotic Adjustment in Expanding Leaves of Tepary Bean )Phaseolus actifolins, Gray) SeedlingsTepary beans perform better than common beans under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential, osmotic potentia4 relative water content and level of free sugars and concentration of K ions within expanding leaves. Two week old seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Tugor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (0.4) occurred in each treatment but the contribution of sucrose and fructose to OA was minor. Some sorbitol was translocated to leaves and contributed to OA. The K ions did not contribute to the OA. A significant decrease in cell size was observed
Effectiveness of Pesticides with Novel Chemistries Against Different Life Stages of the Sweet Potato WhiteflyThe sweet potato whitefly is an insect whose economic importance is continually expanding as it becomes a more efficient vector, increases its fecundity and broadens its host range. To keep pace with its ability to develop resistance to existing classes of pesticides, we have undertaken a program to examine the effectiveness of pesticides with novel chemistries and novel modes of action. Several have shown themselves to be very effective against the various life stages of the sweet potato whitefly. Once these are incorporated in to our arsenal of pesticides, we hope to be able to manage resistance by prudently using these new materials.
Evaluation of Biological Insecticides for Control of Beet Armyworm in LettuceA field study was conducted at Yuma in 1990 to examine the efficacy of several biological insecticide formulations on beet armyworm in seedling lettuce. After a single application at thinning, none of the insecticides adequately reduced larval populations below damaging levels. Reductions in plant stand by larvalfeeding were significantly lower in plots treated with Lannate, Javelin, Biobit and Dipel. Lettuce seedling densities were reduced greaterthan 80% in untreated plots.
Effect of Fungicides Applied at Different Rates on Control of Sclerotinia Leaf Drop of Lettuce -- 1990 Field TestLeaf drop of lettuce, caused by the plant pathogenic fungi Sclerotinia sclerotiorum and S. minor, is found every year in some lettuce fields in Arizona. When environmental conditions are favorable, disease incidence and resulting crop loss can be significant. During the 1989 -90 lettuce season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control Ronilan and Rovral, the two fungicides currently registered for use on lettuce for control of Sclerotinia leaf drop, provided significant disease suppression and increased yields at all rates tested. Bravo and Botran did not control the disease.
Comparison of Different Fungicides for Control of Downy Mildew of Broccoli -- 1991 Field TrialDowny mildew of broccoli, caused by the plant pathogenic fungus Peronospora parasítica, can be found every year in many broccoli fields in Arizona. The severity of the disease is affected by the occurrence and duration of weather conditions favorable for disease development. During the 1990-91 vegetable season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control. Ridomil /Bravo and Bravo, which are currently registered for use on broccoli to control downy mildew, and Aliette, which is currently not registered for use on this crop, provided significant disease control compared to untreated plants. Rovral and Topcop did not control downy mildew on broccoli.
Effect of Sunstainable Versus Conventional Fertilization Practices on Populations of Pythium and Fusarium on Roots of Lettuce in 1990 Field TestThis report focuses upon our efforts to evaluate the effect of sustainable versus conventional fertilization practices on subsequent populations of soil-borne pathogens on lettuce roots. The different fertilization treatments included conventional fertilizer, composted cow manure, and a biological soil conditioner. Near plant maturity, lettuce roots were collected from the field and the populations of Pythium and Fusarium were determined. The lowest population of both of these pathogens was found in the plots fertilized with composted cow manure, while the highest levels of Pythium and Fusarium were detected in the plots treated with conventional fertilizer. Further field studies are planned to confirm these initial findings. Of the two pathogens assayed, Pythium is of greatest concern because of its ability to destroy roots and reduce plant growth and vigor. Species of Fusarium are commonly found in soil and on plant roots and usually do not cause damage to plants unless the plants are under stress.
Potential New Fungicides for Control of Powdery Mildew of Cantaloupe - 1990 EvaluationPowdery mildew of cantaloupe, caused by the plant pathogenic fungus Sphaerotheca fuliginea, is usually found in some melon fields every year. Disease development is favored by low relative humidity, moderate temperatures, and succulent plant growth. In the spring of 1990, potential new fungicides were evaluated for disease control in a field trial All tested materials provided significant control when compared to untreated plants. Bayleton is the only tested material that is currently registered for use on cantaloupe for control of powdery mildew.
Biological Characteristics and Esterase Patterns for Bemisia tabaci Populations, and the Association of Silverleaf Symptom Development in Squash with One PopulationBiological characteristics (oviposition and survival rates) and esterase banding patterns were investigated to evaluate the extent of variation among three test populations of Bemisia tabaci Gennadius (Homoptera. Aleyrodidae). In terms of reproductive capabilities, whiteflies from the cotton (Gossvviurn hirsutum L.) and pumpkin (Cucurbita maxima Duchesne) populations performed similarly on the three host plant species tested. Both populations, which originated from the same wild-type field population, reproduced to higher levels on either cotton and pumpkin hosts than on a poinsettia (Euahorbia vulcherrirna Willdenow) host. In contrast, whiteflies from the poinsettia population differed from cotton- and pumpkin-reared populations in that reproductive capabilities were relatively similar for the three host species tested. For whiteflies from pumpkin and cotton populations a similar and characteristic esterase banding pattern ("A-type") was observed, while whiteflies from the poinsettia population yielded a different banding pattern ("B- type"). In transmission studies, whiteflies from cotton or pumpkin sources did not induce silverleaf (SL) or white stem (WS) symptoms in Cucurbita spp. tested. In contrast, poinsettia population whiteflies were routinely associated with SL and WS symptom phenotypes which developed in Cucurbita spp. following exposure to whitefly adults. From these data, it is possible to correlate a specific esterase banding pattern (A or B) with reproductive capabilities and either the ability or inability to induce SL and WS symptoms.
Nitrogen and Water Effects on Yield, Quality and Tissue Nitrate Concentration in Subsurface Trickle Irrigated MelonsRising water costs and concern for groundwater contamination are encouraging growers to improve irrigation and fertilization efficiency. The objectives of this study were to determine water and fertilizer nitrogen (N) rates leading to optimum yield and harvest quality and to develop a plant tissue test to aid in melon nitrogen fertilization. In 1990, a field experiment consisting of a complete 3x3 factorial arrangement of optimum, sub- and super-optimum rates of urea ammonium- nitrate and water applied through a subsurface trickle irrigation system to cantaloupe, honeyloupe and watermelon was conducted at the Maricopa Agricultural Center. Petioles were sampled from the youngest mature leaf beginning at the early runner stage and then weekly until first harvest. Petiole nitrate concentrations were determined using a high pressure liquid ion chromatograph. Harvested melons were weighed and graded for marketability and soluble solids were determined. Petiole nitrate levels were highly responsive to N fertilizer treatments and accurately quantified visual observations of crop N status. Petiole nitrate results also indicated that later fertilizer split applications occurred after the point of maximum plant uptake. Tensiometer readings suggested that the highest rate of water application led to deep percolation and nitrate leaching where nitrogen fertilizer was excessive. Watermelon showed the clearest yield response to the water and nitrogen treatments. Honeyloupe responded well to high water but poorly to higher nitrogen application rates. Cantaloupe yields responded best to higher nitrogen and medium water levels.
Nitrogen Utilization Efficiency in Melons Using Soluble and Slow Release FertilizersA field experiment was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam soil to compare the nitrogen (N) utilization efficiency achieved using slowrelease and conventional nitrogen fertilizers under subsurface drip irrigated melon production conditions. 'Mirage' watermelon, 'Laguna' cantaloupe and 'Gallicum' honeyloupe were used as the test crops. Single, preplant applications of three slow - release products (methylene urea, coated ammonium sulfate and coated urea) were compared with the use of urea -ammonium nitrate added in either one or three split applications. The total amount of N applied to all treated plots was 100 lbs. per acre. Whole plant samples were taken four times during the season to determine N uptake patterns. Petioles from the youngest fully expanded leaves were sampled on four dates throughout the season to monitor the N status of all plots. At harvest, total and marketable melon yields were determined. In general, the methylene urea treatment was superior to the use of coated (NH₄)₂SO₄ which in turn was far superior to the coated urea product. The split UAN and preplant UAN treatments had the highest numerical values for total N uptake for all three melon types. However, these values were usually not statistically different from the N uptake in response to the three slow- release N treatments. The type of water delivery system may have reduced the potential advantages of using slow-versus fast-release N fertilizers.
Effect of Nitrification Inhibitors on Nitrogen Utilization Efficiency in Sweet CornA field experiment using subsurface drip irrigation was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam soil to evaluate the effect of varying nitrogen (N) sources on the growth and yield of 'Sweetie' 82' sweet corn when applied with, and without four nitrification inhibitors (Nl). The NI treatments included nitrapyrin (N-Serve*), dicyandiamide (DCD), ammonium thiosulfate, and N-Hib Calcium™. Nitrogen was supplied as urea -ammonium nitrate (UAN -32). In addition, an all nitrate source plus a control which received no added N were used. Al! N treated plots received a total of 111 lbs. N acre in split applications at the V3, V6 and the V12 stages. All solutions were applied through buried, perforated PVC tubing to simulate application through the buried drip irrigation system. The inclusion of the nitrification inhibitors with UAN-32 had no significant effect on marketable ear yield, total N uptake or nitrogen use efficiency.