• 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.
    • Commercial Evaluation of Proclaim for Control of Lepidopterous Pests of Lettuce

      Tellez, Tony; Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Proclaim 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.
    • Comparison of Foliar-Applied Insecticides for Whitefly Control in Broccoli

      Umeda, K.; Murrieta, J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Whitefly (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).
    • 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.
    • 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.
    • 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.
    • DPX-MP062 (DuPont) Insecticide Efficacy in Broccoli Study

      Umeda, K.; Stewart, D.; Murrieta, J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      DPX -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.
    • Evaluation of Conventional and Experimental Insecticides for Control of Western Flower Thrips in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Studies 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 Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Provado 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.
    • 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 %.
    • 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.
    • 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.
    • 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.
    • Evaluation of Summer Cover Crops for Rotations with Vegetable Crops

      Umeda, K.; Munda, B.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Five different crops were evaluated in exploratory and observational field studies for potential use as a summer cover crop in a rotation with commonly grown vegetable and field crops. Sesbania ( Sesbania exaltata), cowpea (ViRna unguiculata), sunnhemp (Crotalaria iuncea var. Tropic Sun), sudangrass (Sorghum sudanense cv. Piper), and kenaf (Hibiscus cannabinus) were drill seeded and grown with 2-3 irrigations during the summer months in two field tests. In one test, fresh weight yields were: 7,794 lb/A for sesbania; 10,551 lb/A for sunnhemp; 5,184 lb/A for cowpea; 19,816 lb/A for sudangrass; and 2,390 lb/A for kenaf General observations indicated that adult whiteflies were attracted to sunnhemp at one test site but not at the other. Broccoli, cabbage, and barley were planted in the fall following the cover crops and general observations indicated that sudangrass significantly reduced all of the crops' stand and measurable responses were not evident where the other cover crops were planted.
    • 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.
    • 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
    • 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.
    • Lannate and Larvin Resistance in Beet Armyworms from the Low Desert Regions of Arizona and California

      Kerns, David L.; Tellez, Tony; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Beet 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.
    • Lepidopterous Insect Pest Control with New Insecticides in Cabbage

      Umeda, K.; Murrieta, J.; Stewart, D.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Four 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.
    • Management of Lepidopterous Larvae Under Experimental, Biorational and Conventional Control Programs in Lettuce

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