Vegetable Report 1997
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 1997
- Yuma Vegetable Variety Trials 1996/1997
- Yuma Cantaloupe Variety Trial 1997
- Evaluation of Summer Cover Crops for Rotations with Vegetable Crops
- Evaluation of Postemergence Herbicides for Broccoli Weed Control
- Evaluation of Nortron® Herbicide for Preemergence Weed Control in Onions
- Evaluation of Postemergence Herbicides for Melon Weed Control
- Sweet Corn Herbicide Weed Control
- Response of Desert Lettuce to N Rate and N Management Practice
- Evaluation of Soil Amendments for Lettuce Production in the Desert
- Field Emergence and Seedling Growth of Lettuce as Affected by Pre-Plant/Pre-Emergent Herbicides
- Downy and Powdery Mildew of Lettuce: Comparison of Chemical Management Tools in 1997
- Field Evaluation of Head Lettuce Cultivars for Susceptibility to Sclerotinia Leaf Drop in 1997
- Powdery Mildew of Cantaloupe: Comparison of Chemical Management Tools in 1996
- Downy Mildew of Broccoli: Comparison of Chemical Management Tools in 1997
- Proclaim® Insecticde Efficacy Against Cabbage Looper in Broccoli Experimental Use Permit Field Study
- Pyrethroid Insecticide Comparison in Broccoli
- Insecticides for Whitefly Control in Cantaloupes
- Lepidopterous Insect Pest Control with New Insecticides in Cabbage
- DPX-MP062 (DuPont) Insecticide Efficacy in Broccoli Study
- Comparison of Foliar-Applied Insecticides for Whitefly Control in Broccoli
- Lannate and Larvin Resistance in Beet Armyworms from the Low Desert Regions of Arizona and California
- Review of New Insecticides Under Field Development for Desert Vegetable and Melon Production
- Mating Disruption of Beet Armyworm in Lettuce by Synthetic Pheromone
- Commercial Evaluation of Proclaim for Control of Lepidopterous Pests of Lettuce
- Commercial Evaluation of Confirm for Control of Lepidopterous Pests of Lettuce using Various Applications Techniques
- Management of Lepidopterous Larvae Under Experimental, Biorational and Conventional Control Programs in Lettuce
- Evaluation of Foliar Insecticide Approaches for Aphid Management in Head Lettuce
- Evaluation of Conventional and Experimental Insecticides for Control of Western Flower Thrips in Head Lettuce
- Temporal and Diagnostic Mortality of Beet Armyworm Larvae to Selective Insecticides in Head Lettuce
- Temporal and Diagnostic Mortality of Cabbage Looper Larvae to Selective Insecticides in Head Lettuce
- Seasonal Dynamics and Management of Whiteflies on Melons and Vegetables in the Desert Southwest
- Defining the Risk of Resistance to Imidacloprid in Arizona Whitefly
Defining the Risk of Resistance to Imidacloprid in Arizona WhiteflyA resistance management program for imidacloprid was initiated in Arizona in 1995, the ultimate goal of which is to sustain the efficacy of this insecticide against Bemisia. The current paper reviews our progress toward defining the risk of resistance to imidacloprid in Arizona whiteflies. Bioassay methods for adult whitefly consisted of a 1 day hydroponic uptake by cotton seedlings, followed by a 2 day exposure period. Results from statewide monitoring indicate that whitefly populations throughout Arizona are susceptible to imidacloprid; however, slight increases in resistant whiteflies were observed in 1996, as compared to 1995. Thus far, selection studies with various Arizona whitefly populations have not led to reduced susceptibility to imidacloprid. In a study exploring the influences of different cropping systems on imidacloprid use, we found no major differences in susceptibility to imidacloprid between populations of whiteflies in central and southwestern Arizona. Continued effective management of Arizona whitefly will, in part, hinge on our ability to more effectively integrate our knowledge of whitefly biology with resistance management strategies.
Seasonal Dynamics and Management of Whiteflies on Melons and Vegetables in the Desert SouthwestFor the past 5 years, Arizona growers have been faced with the challenge of managing whiteflies populations to prevent yield reduction and loss of quality of their vegetable and melon crops. A large cooperative research effort was directed statewide to better understand how whiteflies develop on the numerous host -crops available and the environmental factors that influence their survival throughout the year. This information was used to develop short and long term management approaches for controlling whitefly populations. We quickly discovered that preventing whiteflies from colonizing plants was the key to successful management of whitefly populations in vegetable and melon crops. This report attempts to summarize what we presently understand about factors that influence the seasonal abundance of whiteflies in southern Arizona cropping systems. Non-chemical and chemical management approaches that have been developed by researchers and implemented by the agricultural communities are discussed
Temporal and Diagnostic Mortality of Cabbage Looper Larvae to Selective Insecticides in Head LettuceSeveral new insecticide chemistries were evaluated and compared with standard chemistries for temporal and diagnostic mortality of cabbage looper in lettuce. Three field bioassays of small and large larval mortality were conducted at pre-thinning, thinning, and postthinning, stages of lettuce. The compounds with translaminar activity (Alert, Success, and Proclaim) appear to be have the most rapid "knockdown activity" with 100% mortality consistently occurring by 1 -2 DAT. Because of their rapid activity, a large proportion of larvae are found dead on the plants. The products that need to be ingested to cause larval mortality (Larvin Confirm, Neemix, Crymax, Cryolite, MP 062) generally varied significantly in temporal mortality and in efficacy against larvae. Unlike the translaminar products, a large proportion of larvae on were often found missing from treated plants. The results of this study provide basic guidelines concerning the activity and assessment of the performance of these materials in the field PCAs and growers will ultimately be able to develop specific use patterns for these materials within their individual lettuce pest management programs.
Temporal and Diagnostic Mortality of Beet Armyworm Larvae to Selective Insecticides in Head LettuceSeveral new insecticide chemistries were evaluated and compared with standard chemistries for temporal and diagnostic mortality of beet armyworm in lettuce. Field and lab bioassays of small and large armyworm mortality were conducted at pre- thinning thinning postthinning and harvest stages of lettuce. Results from both the field and laboratory indicated similar trends for the temporal activity of the products. The compounds with translaminar activity (Alert, Success, and Proclaim) appear to be have the most rapid "knockdown activity" with 100% mortality consistently occurring by 1-2 DAT. Because of their rapid activity, a large proportion of larvae are found dead on the plants. The products that need to be ingested to cause larval mortality (Larvin, Confirm, Neemix, Crymax, Cryolite, MP 062) generally varied significantly in temporal mortality and in efficacy against larvae. Unlike the translaminar products, a large proportion of larvae on were often found missing from treated plants The results of this study provide basic guidelines concerning the activity and assessment of the performance of these materials in the field PCAs and growers will ultimately be able to develop specific use patterns for these materials within their individual lettuce pest management programs.
Evaluation of Conventional and Experimental Insecticides for Control of Western Flower Thrips in Head LettuceStudies were conducted in small plot field trials to evaluate the efficacy of several experimental and conventional insecticide chemistries against western flower thrips in head lettuce. Results from two trials using new experimental compounds showed that several insecticides have potential for management of thrips populations. All of the products appear to be good candidates for thrips control and had efficacy against adults and nymphs. Success and Fipronil consistently provided comparable control to the standard Lannate/Ammo. In the trial evaluating conventional compounds, Orthene/Mustang and Lannate/Ammo combinations provided the best control of both adult and nymphs. Plant size and temperature may be important factors contributing to the efficacy of these products.
Evaluation of Foliar Insecticide Approaches for Aphid Management in Head LettuceProvado insecticide (imidacloprid) was compared to Admire and other standard insecticides for management of aphids in head lettuce in Yuma 1995 and 1996. Foliar applications of Provado appear to provide an alternative method of controlling aphids on lettuce comparable to prophylactic applications of Admire. The prevention of aphid colonization in lettuce heads with Provado may depend greatly on the timing and frequency of applications before harvest occurs. These studies and other studies on spinach suggest that more than one application of Provado will be necessary to adequately suppress aphid contamination in heads. The label suggests that applications be timed 5-7 apart. Our data tends to support this recommendation. Furthermore, timing applications should be based on days to harvest, level of aphid colonization and duration of aphid migration.
Management of Lepidopterous Larvae Under Experimental, Biorational and Conventional Control Programs in LettuceA large block experiment was conducted at the Yuma Ag Center to compare the field performance of three lettuce management programs for control of lepidopterous larvae. Conventional, experimental and biorational insecticides were sprayed to control beet armyworm, cabbage looper and Heliothis species throughout the growing season. Differences in populations of total larvae among the four treatments, relative to insecticide treatments and timing of application were observed throughout the season. In general, the standard and experimental treatments provided the most consistent control of lepidopterous larvae following each application. Harvest data showed that the spray regimes had a significant influence of head lettuce yield or quality. Maturity and quality were significantly reduced in the untreated control. An economic analysis shows that net returns varied widely among the management programs at different market prices. In conclusion, this study provides preliminary data to support the need for more development of experimental and biorational insecticide products as alternatives to conventional management programs in desert lettuce production.
Commercial Evaluation of Confirm for Control of Lepidopterous Pests of Lettuce using Various Applications TechniquesConfirm was evaluated in head lettuce for control of lepidopterous pests when applied by air, and when applied by ground at 4, 8 and 12 mph. By air Confirm may not provide commercially acceptable control when used alone. Confirm must be ingested to exhibit activity and aerial applications may not provide adequate spray coverage. When used by ground, applicators should avoid exceeding 8 mph, again because good spray coverage may be compromised.
Commercial Evaluation of Proclaim for Control of Lepidopterous Pests of LettuceProclaim 1.6 was evaluated in head lettuce in side-by-side large plot aerial and ground application demonstrations compared to commercial standard treatments. Proclaim consistently provided excellent control of beet armyworm and cabbage looper larvae. Worm control by Proclaim was equivalent to, or better than the commercial standards.
Mating Disruption of Beet Armyworm in Lettuce by Synthetic PheromoneThe beet armyworm pheromone dispenser, Yotoh-con-S, was evaluated for its ability to inhibit mate location and subsequent population growth of beet armyworm in head lettuce. Pheromone dispensers were very effective in preventing male beet armyworm moths from locating point pheromone sources. Pheromone dispensers also appeared to result in an approximately 75 % reduction in beet armyworm larvae relative to untreated fields.
Review of New Insecticides Under Field Development for Desert Vegetable and Melon ProductionThe efficacy and field performance of new insecticides for control of insects on vegetables and melons under desert growing conditions has been investigated in small plot trials for the past several years at the Yuma Agricultural Center. Our objective has been to determine how new chemistries will fit into the growers management programs in Arizona. Thus, our research programs have been focused on studies to determine how to integrate these new chemicals into our local management programs in the most cost/effective way possible. This document was created to provide you with an overview of new insecticide chemistries being developed by the Agrichemical Industry for use in vegetables. The first part of this report concisely describes the new types of chemistries being developed The tabular information presented is a summary of the efficacy and activity of the new compounds based on research we have conducted at the Yuma Agricultural Center.
Lannate and Larvin Resistance in Beet Armyworms from the Low Desert Regions of Arizona and CaliforniaBeet armyworm populations were collected in 1996-97 from spinach, melons, lettuce and alfalfa in Arizona and California, and tested for resistance to topical applications of Lannate. Resistance levels were found to be low to very high. The lowest level of resistance detected came from Blythe, CA, having no detectable resistance to Lannate, and from Parker, AZ, having a resistance level of approximately 24 fold. The highest level of resistance detected was a 685 fold increase, from a population collected from alfalfa in Imperial County, CA. In Yuma, larvae collected from alfalfa following an insecticide application that included Lannate, was 4.43 fold more resistant than the pre-application population. Only very low levels of resistance were found to Larvin, and no evidence of cross -resistance between Lannate and Larvin was found. Larvae resistant to topical applications of Lannate were found to be susceptible to Lannate given orally. Lannate resistance appears to be due to cuticular penetration and/or cuticular metabolism.
Comparison of Foliar-Applied Insecticides for Whitefly Control in BroccoliWhitefly (Bemisia tabaci also known as B. argentifolii) control in fall planted broccoli is difficult to achieve with foliar-applied insecticides and two treatments were compared and demonstrated a relative reduction of the immature stage of whitefly. Capture® (bifenthrin) plus Thiodan® (endosulfan) as a tank-mix applied two times significantly reduced the number of whitefly immatures (9/leaf) compared to the untreated check (71/leaf). Provado® (imidacloprid) following two applications reduced the number of immature whiteflies by only slightly more than 50% (38/leaf).
DPX-MP062 (DuPont) Insecticide Efficacy in Broccoli StudyDPX -MP062 (Dupont) insecticide was applied two times in broccoli for cabbage looper (Trichoplusia ni. CL) control and demonstrated efficacy comparable or superior to methomyl (Lannate®) or esfenvalerate (Asana®). DPX-MP062 0.025 to 0.065 lb AI/A alone or in combination with Lannate significantly reduced the number of medium to large sized CL larvae relative to the untreated broccoli following each application.
Lepidopterous Insect Pest Control with New Insecticides in CabbageFour experimental insecticides being developed for lepidopterous insect control in vegetable crops were applied on cabbage and demonstrated efficacy against cabbage looper (Trichoplusia ni, CL). Chlorfenapyr (Alert®), tebufenozide (Confirm®), spinosad (Success®), and emamectin- benzoate (Proclaim®) reduced the number of larger cabbage loopers following multiple applications. The experimental insecticides were comparable or superior to the commercially available standard treatments of thiodicarb (Larvin®), methomyl (Lannate®), or cryolite (Kryocide®). Evaluations at 7 days after treatment (DAT) showed that Success controlled CL so that no medium to large -sized larvae were observed. Alert, Confirm, and Proclaim were highly effective and less than 0.3 CL/plant were detected. The untreated cabbage had 0.5 to 1.1 CL/plant that were medium to large-sized at various observation dates.
Insecticides for Whitefly Control in CantaloupesSeveral experimental insecticide treatments alone or in combinations were evaluated and demonstrated efficacy against Bemisia argentifolii [silverleaf whitefly (WF) also known as sweet potato WF, B. tabaci]. At each rating date following each of four applications, the number of adult and immature WF were reduced relative to the untreated check CGA-215944 (Ciba) treatment combinations were similar at each rating date and significant differences could not be distinguished between the addition of fenoxycarb (Ciba) or CGA-59205 (Ciba). Combinations of insecticides or alternating with insect growth regulators (IGR's) also significantly reduced numbers of WF adults and immatures similar to the standard treatment of bifenthrin (Capture®) plus endosulfan. A single application of pyriproxyfen (Valent) was followed by different treatments [endosulfan followed by fenpropathrin (Danitol®) plus methamidaphos (Monitor®) followed by endosulfan] at each application date. Buprofezin (Applaud®) was combined or alternated with endosulfan at each application and similar reduction of WF was observed. Pyridaben (BASF) did not adequately reduce WF adults and immatures relative to the standard treatment in this test. The Ciba compounds and single or multiple applications of the IGR's, pyriproxyfen and Applaud were highly effective in substantially reducing WF immatures and adults in this test.
Pyrethroid Insecticide Comparison in BroccoliSeveral pyrethroid insecticides were evaluated and compared for efficacy against lepidopterous insect pests in broccoli. Zeta-cypermethrin (Mustang®) was compared at two rates, tralomethrin (Scout X-tra®) formulations were compared, lambda-cyhalothrin (Karate®), and esfenvalerate (Asana®) were evaluated for efficacy against cabbage looper (Trichoplusia ni. CL). Following each of the applications, most of the treatments reduced the number of larger sized CL relative to the untreated check. The two rates of Mustang performed similarly as did the two formulations of Scout X-tra, emulsifiable concentrate versus gel.
Proclaim® Insecticde Efficacy Against Cabbage Looper in Broccoli Experimental Use Permit Field StudyProclaim® insecticide (emamectin benzoate, MK -244, Merck Research Laboratories) was applied two times during the broccoli growing season for lepidoperous insect control. The primary pest was cabbage looper (Trichoplusia ni CL) and very few beet armyworm (Spodoptera exigua). After the second application at 1, 2, and 3 weeks after treatment (WAT), Proclaim reduced the number of CL in the broccoli relative to the untreated check. The number of large larvae observed in the Proclaim treated broccoli was one-half of that found in the untreated broccoli. Proclaim efficacy to reduce CL was comparable to the standard treatment of Larvin® (thiodicarb) plus Asana® (esfenvalerate). At harvest, the Proclaim treated broccoli had 20% infested crowns compared to 28% for the standard treatment and 44% in the untreated.
Downy Mildew of Broccoli: Comparison of Chemical Management Tools in 1997Downy mildew of broccoli is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of weather conditions favorable for disease development. Potential new fungicides were evaluated for disease management in a 1997 field trial. A moderate degree of downy mildew developed by crop maturity. All tested compounds except Trilogy provided significant reductions in the severity of disease compared to no treatment at all. Several products not presently registered for use on broccoli show promise as potential new materials for disease management.
Powdery Mildew of Cantaloupe: Comparison of Chemical Management Tools in 1996Powdery mildew of cantaloupe and other melons occurs every year in Arizona; however, the incidence and severity of the disease is quite variable. This disease, caused by the plant pathogenic fungus Sphaerotheca fuliginea, is favored by moderate temperature and relative humidity, succulent plant growth and reduced light intensity. Potential new fungicides were evaluated for disease management in a field trial conducted in the spring of 1996. All tested products significantly reduced the level of disease compared to nontreated melon plants. In addition to compounds already registered for use on cantaloupe, such as Microthiol Special, Reach, Benlate, Bayleton and Bravo, the list of efficacious nonregistered agrochemicals included Quadris, Procure, BAS-490, and Rally. The possible availability of new disease management tools in the future for powdery mildew of cantaloupe and other melons could enhance our efforts to reduce the development of resistance to these fungicides by the pathogen.