• Optimal Soil Placement and Application Method of Admire® for Sweetpotato Whitefly Control in Head Lettuce

      Palumbo, John; Kerns, David; Sanchez, Charles; Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      The effects of Admire formulation and soil placement on colonization by sweetpotato whitefly, Bemisia tabaci (Gennadius), at three plant growth stages of lettuce, Lactuca sativa L., were evaluated in experimental and commercial lettuce plots in 1993-1994. We also evaluated the effects of Admire treatments on yield response and incidence of chlorosis associated with whitefly control. Admire placement had a significant affect on whitefly colonization in lettuce throughout the experimental period. Whitefly densities on lettuce varied at each plant stage relative to depth of placement within the lettuce seed bed. Applications made to the soil surface and at 1.5 inch sub-seed furrow followed by irrigation, provided the most consistent control of whitefly nymphs in both small plot and on -farm lettuce plots. These Admire soil treatments also prevented reductions in head size and incidence of leaf chlorosis associated with whitefly colonization in lettuce. Our data suggest that incorporation of Admire into the upper 1.5 - 2 inches of soil below the seed furrow is optimal for absorption and translocation by lettuce roots. Admire soil treatments may provide a more environmentally suitable and effective alternative to control of whiteflies in lettuce than is currently possible with foliar insecticide reatments.
    • Whitefly Control in Arizona Vegetables: Development of a Resistance Management Program for Imidacloprid (Admire®)

      Williams, Livy III; Dennehy, Timothy J.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      In 1995 we initiated a resistance management program aimed at sustaining the efficacy of Admire®. This paper delineates the groundwork for the program, and describes methodological and conceptual advances toward our goal. Bioassay methods developed for adult whitefly consisted of a 1 day hydroponic uptake procedure using cotton seedlings. A reliable mortality criterion was also established. Results from a statewide survey suggested slight geographic variation in whitefly susceptibility to Admire®. Future studies will 1) continue to monitor susceptibility throughout Arizona, 2) evaluate the risk of resistance to whitefly populations in commercial greenhouses, and relate this to field populations, and 3) characterize the development of resistance in relation to cropping systems and spatial dynamics of whitefly. The overall objective of these investigations is to determine if a sustainable use strategy can be identified for Admire®.
    • Sweet Corn Tolerance and Herbicide Weed Control

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      No observable injury was evident by any herbicide treatment on any of the twelve sweet corn varieties during the season. Overall, pendimethalin (Prowl®) treatments applied preemergence (PREE) provided very good control ( >87 %) of all weeds rated. Metolachlor (Dual®), EPTC plus safener (Eradicane®), dimethanamid (Frontier®), and cyanazine ( Bladex®) treatments gave good control ( >80 %) of pigweeds ( Amaranthus sp.) and purslane (Portulaca oleraceq) with annual yellow sweetclover (Melilotus ocf`icinalis) not adequately controlled. All treatments except Bladex alone gave good control of volunteer sudangrass.
    • Insecticides for Whitefly Control in Cantaloupes

      Umeda, K.; Fredman, C.; Fredman, R.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Several experimental insecticide treatment combinations were evaluated and demonstrated very good efficacy against Bemisia argentifolii [silverleaf whitefly (WF) also known as sweetpotato WF, B. tabaci]. Adults and immatures were most effectively reduced compared to the untreated check by pyriproxyfen (S-71639, Valent) treatments and fenpropathrin (Danitol®) plus acephate (Orthene®). CGA-215944 (Ciba) plus fenoxycarb (Ciba) treatments compared favorably with many of the pyrethroid combination treatments. Registered products esfenvalerate (Asana®), endosulfan (Thiodan®), cypermethrin (Ammo®), naled (Dibrom®), and oxydemeton-methyl (Metasystox-R®) complemented many of the combination treatments to reduce WF relative to the untreated check
    • Late Season Biological Control of Whiteflies in Fall Cantaloupe Using Formulations of Beauveria Bassiana

      Knowles, Tim C.; Jaronski, Stefan T.; McGuire, Jerry; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Beauveria bassiana is a naturally occurring fungal disease of insects that has been shown to be an effective biological control against whiteflies in cotton and vegetable crops. Six treatments were initiated in drip irrigated fall cantaloupe on October 2, and repeated on October 9 and 23. The six treatments consisted of 1) a check or unsprayed plot; 2) 0.5 lb. Mycotrol WP/acre; 3) 1 Ib. Mycotrol WP /acre; 4) 1 pt. Mycotrol ES/acre; 5) 0.5 lb. Mycotrol WP /acre + pyrethroid tank mix; and 6) 12 oz. Naturalis-L/acre. Under moderate to light sweetpotato whitefly pressure, the Mycotrol formulations provided significant control (68-79%) compared to unsprayed check plots, and were superior to Naturalis-L formulation whose effects were relatively short lived. Mycotrol WP applied in three applications at the labeled rate of 1 lb. product/acre had the cumulative effect of maintaining adult whitefly leaf counts below the currently recommended economic threshold of 3 per leaf at 28 days after treatment initiation, under the conditions of this study.
    • Broccoli Preemergence Herbicide Weed Control Studies

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Exploratory field studies conducted in broccoli showed that clomazone (Command®) and isoxaben (Gallery®) were extremely phytotoxic to broccoli when applied preemergence (PREE) on the soil surface after planting. Both offered good weed control of the weeds present. Napropamide (Devrinol®) caused moderate crop injury and marginally acceptable weed control.
    • Mulching Cantaloupes with Plastic at Yuma 1996

      Oebker, N. F.; Sanchez, C. A.; Wilcox, Mark; Palumbo, J. C.; Matheron, M. E.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Six mulches were compared to no mulch on cantaloupes at Yuma in the Spring of 1996. The IRT film and black mulches caused "Mission" cantaloupes to produce significantly higher early yields than white mulch or no mulch. Silver mulch gave good early and total yields. All mulches seemed to favor total production but in this test differences for total yields between mulched and non-mulched plots were not significant.
    • Management of Sclerotinia Leaf Drop on Lettuce: Efficacy of Fungicides in 1996 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Leaf drop of lettuce is caused by the plant pathogenic fungi Sclerotinia minor and S. sclerotiorum. Cool and moist environmental conditions favor disease development. Potential new fungicides were evaluated in a field trial for management of this disease in 1996. For plots containing Sclerotinia minor, all compounds and rates tested significantly reduced the number of diseased heads compared to plots not treated with a fungicide. All treatments except Ronilan at the 0.5 lb. a. i./A rate yielded a significantly higher number of marketable heads compared to nontreated plots infested with S. minor. For plots containing S. sclerotiorum, all materials except the Ciba compound at the low and high rates decreased the number of diseased heads and increased the number of marketable heads compared to nontreated plots.
    • Air-Assisted Electrostatic Application of Pyrethrois and Endosulfan Mixtures for Sweetpotato Whitefly Control and Spray Deposition in Cauliflower

      Palumbo, John; Coates, Wayne; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Pyrethroid and endosulfan mixtures applied at full and reduced rates with three application methods (air-assisted electrostatic, air-assisted hydraulic, and standard hydraulic sprayers) were evaluated in field studies in 1992 and 1993 for control of sweetpotato whitefly, Bemisia tabaci-strain B (Genn.), also known as silverleaf whitefly, Bemisia argentifolii Bellows and Perring, and spray deposition on caulker, Brassica oleracea L. Based on adult suppression, improved control of whiteflies was achieved with full and reduced rates of the air-assisted electrostatic sprayer following two applications in 1992, but percent reduction of adults did not differ significantly among the application methods when full rates of insecticide were applied in 1993. Control based on immature colonization indicated that the air-assisted electrostatic sprayer was the only spray method to significantly reduce nymph densities when compared with the control in 1992, but differences in numbers of eggs, nymphs and eclosed pupal cases varied among application methods and rates of active ingredient in 1993. Comparisons of cauliflower harvest dates indicated that the air -assisted electrostatic sprayer did not provide significantly better control than the other application methods when used at similar rates. Spray deposition with the air-assisted electrostatic application technique was variable throughout these studies with no clear trends being observed. Our results suggest the air-assisted electrostatic sprayer may offer a means to control sweetpotato whitefly with a 50% reduction in insecticide usage.
    • Residual Activity of New Insecticide Chemistries Against Beet Armyworm in Lettuce

      Kerns, David L.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Three new insecticide chemistries (Alert, Success and Confirm) were evaluated and compared with standard chemistries for residual activity to beet armyworm in lettuce. Lettuce was treated in the field with the insecticides and left for 0, 3, 5 and 7 days. Leaves from treated plants were then brought into the laboratory where second instar beet armvworms were reared on them. Mortality was estimated 5 days after the worms were placed on the leaves. Bioassay were conducted at the thinning, heading, and harvest stages of lettuce. Under high temperature and light intensity, only Alert and Confirm provided the best residual control of beet armyworm, exhibiting good activity for about 3 days after application. Success had better residual activity than Lannate, and both were better than Xentari. Under cool temperatures and low light intensity conditions, Alert, Confirm and Larvin exhibited good activity for at least 5 days following an application, (7 days or greater for Alert and Confirm). Lannate and Xentari both had greater residual activity late in the season, but were not as effective as Alert, Confirm or Larvin. Late season activity of Success did not appear to differ much from early season observations, and did not appear to provide more than 3 days residual activity.
    • Evaluation of Insecticides for Aphid Control in Cabbage

      Umeda, Kai; Fredman, Chris; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Experimental insecticides CGA-215944 (Ciba), pyriproxyfen (S-71639, Valent), and RH-7988 (Rohm and Haas) demonstrated very good efficacy in reducing the aphid population in cabbage. Fipronil (Rhone-Poulenc) was not as effective in controlling the aphids relative to the other treatments. Acephate (Orthene®), chlorpyrifos (Lorsban™), and naled (Dibrom®) were highly effective relative to the untreated check.
    • Management of Downy Mildew on Broccoli: Efficacy of Fungicides in 1996 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      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 field trial conducted in 1996. Disease pressure was moderate and all tested fungicides except Ridomil MZ 72 and one Ciba G + Mancozeb treatment significantly reduced the number of downy mildew lesions on leaves compared to plants not treated with a fungicide. The level of disease reduction provided by all chemical treatments was equivalent to that given by Aliette and Bravo, two fungicides currently available for control of downy mildew on broccoli.
    • Cauliflower Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Effect of a Plant Growth Regulator on Green Beans Grown for Processing

      Rethwisch, Michael D.; Beckstead, Dick; Parker, Larry; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Three rates of the plant growth regulator Foliar Triggrr were applied to green beans grown for processing at 5% bloom. The 6 oz rate increased yields of size 1 and 2 beans compared to all other treatments and the untreated check and had the fewest size 3 beans (which would be culls). The 11 oz rate was similar to the untreated check while the 16 oz rate decreased yields. Total bean numbers per plant were similar. Although treatment differences in this experiment were not statistically significant, a yield increase of 10.2% for the 6 oz rate compared with the untreated check may well result in increased economic returns.
    • Timing and Frequency of Provado® Applications for Management of Aphid Populations in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      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.
    • Soil-Applied Herbicide Weed Control in Cantaloupes

      Umeda, Kai; Fredman, Chris; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Several registered and exploratory herbicides were effective for broadleaved weed control when applied preplant incorporated or preemergence in cantaloupes. Bensulide (Preface), clomazone (Command®), cyanazine (Bladex®), dimethanamid (Frontier®), ethafluralin (Curbit®), metolachlor (Dual ®), pendimethalin (Prowl®), trifluralin, dithiopyr (Rohm and Haas), and thiazopyr (Rohm and Haas) gave marginally acceptable control of most weeds. Crop injury was observed for some treatments of Frontier, Prowl, napropamide (Devrinol®), and Command. As the season progressed, groundcherry (Physalis wrightii) was not adequately controlled by any treatment.
    • Broccoli Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Admire® Aphid Control in Spring Cabbage

      Umeda, Kai; Fredman, Chris; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Imidacloprid (Admire®) was applied at planting time in anticipation of providing aphid control in cabbage for spring harvest. In three commercially treated cabbage fields, Admire reduced the number of cabbage (Brevicoryne brassicae) and green peach aphids (Myzus persicae). Two rates of Admire, 10 and 20 oz/A appeared to be similar in performance for efficacy against aphids. Depth of placement of Admire in the soil below the seed appears to have some influence on the efficacy and consistency of performance. Much fewer aphids and greater consistency was observed when Admire was placed at 1-inch depth below the seed compared to 3- to 4-inches below the seed.
    • Cantaloupe Variety Trials 1996

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Crisphead Lettuce Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)