• 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.
    • 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.
    • 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 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.
    • 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.
    • 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.
    • 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.
    • Yuma Cantaloupe Variety Trial 1997

      Wilcox, Mark; Oebker, Norman F.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
    • 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
    • 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.
    • 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.
    • 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 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.
    • 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.
    • 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.
    • 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.
    • Yuma Vegetable Variety Trials 1996/1997

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