• Proclaim® Insecticde Efficacy Against Cabbage Looper in Broccoli Experimental Use Permit Field Study

      Umeda, K.; Murrieta, J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Proclaim® 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 and Powdery Mildew of Lettuce: Comparison of Chemical Management Tools in 1997

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Downy and powdery mildew are caused by the plant pathogenic fungi Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development of downy mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for management of these diseases in 1997. A very low level of downy mildew occurred during this trial; however, all treatments significantly reduced the number of leaf lesions compared to nontreated lettuce plants. Powdery mildew was quite intense at crop maturity and was significantly lower, compared to nontreated lettuce, on plants treated with Microthiol Special, BAS 490 + Bravo Weather Stik, Quadris, and two additional treatments not usually found to reduce this disease.
    • Commercial Evaluation of Confirm for Control of Lepidopterous Pests of Lettuce using Various Applications Techniques

      Kerns, David L.; Tellez, Tony; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Confirm 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.
    • Review of New Insecticides Under Field Development for Desert Vegetable and Melon Production

      Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      The 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.
    • Downy Mildew of Broccoli: Comparison of Chemical Management Tools in 1997

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Downy 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.
    • Evaluation of Nortron® Herbicide for Preemergence Weed Control in Onions

      Umeda, K.; Gal, G.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      An exploratory field study was conducted to evaluate the efficacy and safety of Nortron® (ethofumesate) herbicide for potential use in an onion weed control program. A rate range of 1.0 to 2.5 lb AI/A applied preemergence (PREE) demonstrated good safety on onions and no injury or crop stand reduction was observed. Sowthistle was the most numerous weed present and Nortron did not reduce it relative to the untreated check. Dacthal® (DCPA) significantly reduced the number of sowthistle relative to the untreated and to Nortron treatments. Onion height was reduced by Dacthal about 40 %.
    • Yuma Vegetable Variety Trials 1996/1997

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
    • Sweet Corn Herbicide Weed Control

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      The sequence of preemergence (PREE) herbicide metolachlor (Dual II®) followed by postemergence (POST) herbicide mixture of primisulfuron plus prosulfuron (Exceed®) provided season-long near complete weed control in sweet corn. Preplant incorporated (PPI) treatments of dimethenamid (Frontier®), EPTC plus safener (Eradicane®), and herbicide mixture FOE 5043 plus metribuzin (Axiom®, Bayer) provided effective weed control for most of the season. Similar effective weed control was observed for PREE treatments of pendimethalin (Prowl®), Frontier, and Axiom.
    • Field Emergence and Seedling Growth of Lettuce as Affected by Pre-Plant/Pre-Emergent Herbicides

      Sill, David W.; Tickes, Barry; Carey, Lisa A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Pre plant and pre- emergence herbicides are commonly used in lettuce production. We investigated possible effects the herbicides benefin (Balan), pronamide (Kerb) and bensulfide (Prefar) had on emergence and seedling growth of several iceberg lettuce varieties that had been primed and pelleted by seed enhancement companies The herbicide Prefar and a mixture of Balan + Prefar had the greatest impact on dry weight regardless of variety, while seedlings grown on Kerby plots were not significantly different than seedlings from untreated plots. Dry weight accumulation and field emergence were influenced significantly by pellet types and priming methods.
    • Powdery Mildew of Cantaloupe: Comparison of Chemical Management Tools in 1996

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Powdery 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.
    • Evaluation of Postemergence Herbicides for Melon Weed Control

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Bentazon (Basagran®) at 0.5 to 2.0 lb a. i. /A, halosulfuron (Permit®) at 0.025 to 0.10 lb a.i A, and pyridate (Lentagran®) at 0.25 to 1.5 lb a.i. /A were applied postemergence on cantaloupe and watermelon. Bentazon was marginally safe on cantaloupes and controlled purslane and pigweeds. Morningglory and Wright's groundcherry were not effectively controlled by bentazon. Bentazon appeared to be less injurious to watermelons relative to cantaloupes. Halosulfuron was safe on both cantaloupes and watermelons (<15% injury). Halosulfuron at greater than 0.05 lb /A was effective in controlling only Hyssop spurge and London rocket. In one test, halosulfuron gave acceptable control (85 %) of morningglory. Purslane and groundcherry were not controlled by halosulfuron. Pyridate was not safe on cantaloupes causing severe crop stand reduction. Pyridate was safer on watermelons and caused marginally acceptable injury, however, weed control was not effective against groundcherry, spurge or London rocket. Pyridate appeared to give acceptable control of morningglory in one test.
    • Temporal and Diagnostic Mortality of Cabbage Looper Larvae to Selective Insecticides in Head Lettuce

      Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Several 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 Lettuce

      Palumbo, John C.; Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Several 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.
    • Response of Desert Lettuce to N Rate and N Management Practice

      Sanchez, Charles A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Lettuce produced in the desert typically shows large yield responses to N fertilization. However, concern about the potential threat of nitrate-N to ground water has prompted additional studies aimed at developing improved N management practices. Field experiments were conducted between 1992 and 1994 to evaluate the response of iceberg lettuce to N rate and N management practice. The use of controlled release N sources (CR19 were compared to a soluble N fertilizer applied preplant (PP), and a soluble N fertilizer applied in split-sidedress applications (SD). Rates of N fertilizer application ranged from 0 to 300 kg ha⁻¹. Lettuce generally showed significant responses to N rate and N management practice. However, response to management practice varied by site-season. When conditions for N losses were high, SD and CRN management strategies were superior. However, in other site seasons SD management sometimes resulted in inferior head quality and marketable yield when compared other management strategies. Data averaged over six -site seasons shows improved yield and quality to CRN management strategies compared to PP and SD strategies. Although the controlled-release fertilizers used in these experiments cost three times more the conventional soluble sources used, preliminary analysis shows the use of CRN strategies would sometimes be economically favorable.
    • Yuma Cantaloupe Variety Trial 1997

      Wilcox, Mark; Oebker, Norman F.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
    • Field Evaluation of Head Lettuce Cultivars for Susceptibility to Sclerotinia Leaf Drop in 1997

      Wilcox, Mark; Matheron, Michael; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Leaf drop of lettuce is caused by the plant pathogenic fungi Sclerotinia minor and S. sclerotiorum. Cool and moist environmental conditions favor disease development. Sixteen diffirent cultivars of head lettuce were evaluated in the field for susceptibility to Sclerotinia leaf drop in plots inoculated with sclerotia of Sclerotinia minor or S. sclerotiorum. Significant differences were detected among the tested cultivars in the amount of lettuce plants killed by Sclerotinia minor. On the other hand, there were no significant differences among tested cultivars in the number of plants destroyed by Sclerotinia sclerotiorum
    • Defining the Risk of Resistance to Imidacloprid in Arizona Whitefly

      Williams, Livy III.; Dennehy, Timothy J.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      A 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.
    • Evaluation of Postemergence Herbicides for Broccoli Weed Control

      Umeda, K.; Stewart, D.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Second year field studies continued to evaluate and determine efficacy and safety of postemergence herbicides for broccoli weed control. Goal® 2XL. a newly introduced formulation of oxyfluorfen. severely injured broccoli after application. London rocket (Sisvmhrium irio) control was not acceptable at less than 80%. Pvridate (Lentagran®) and clopyralid (Stinger®) were relatively safe on broccoli but did not affect London rocket.
    • Insecticides for Whitefly Control in Cantaloupes

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Several 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.
    • Evaluation of Soil Amendments for Lettuce Production in the Desert

      Sanchez, C. A.; Silvertooth, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Two field studies were conducted during the 1993-1994 season to evaluate the response of lettuce to soil applied amendments. Treatments included gypsum, polymaleic acid (Spersal), and two acid products (N-phuric and Phos-phuric). Gypsum rates (0, 2240, and 4480 kg /ha) were the main plots and other soil amendments were subplot randomized within the mainplots. Overall, gypsum reduced early growth and vigor of lettuce. Gypsum had no effects on marketable yield and quality parameters in experiment 1, but the highest gypsum rate (4448 kg /ha) decreased marketable yield in experiment 2. There were no differences in plant stands due to subplot treatments. However, there were differences in earlygrowth and vigor. In experiment 1, both "N-phuric" and "Phos-phuric" increased early lettuce growth compared to the control. In experiment 2, Phos-phuric was superior to N-phuric. In experiment 1, the benefits of early growth and vigor to the "N-phuric" and "Phos-phuric" carried to harvest where marketable yield and quality were significantly increased. Spersal did not significantly effect yield and quality of lettuce in either experiment.