• 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.
    • Cabbage Variety Trials 1995/96

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

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Trends in the Temporal Distribution and Host Plant Relations During 1988-1994, and Virus-vector Characteristics of Two Whitefly Populations in Arizona

      Brown, J. K.; Oebker, Norman F.; Department of Plant Sciences (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      The abrupt and widespread introduction and establishment of the B type whitefly B. tabaci (Genn.) (also B. argentifollii) in Arizona in approximately 1987-1990 has given rise to unprecedented losses in vegetable and fiber crops in Arizona, and elsewhere throughout the sunbelt states. This report documents the discovery and the tracking of B type whitefly over time in Arizona crop and weed species, and reports important biological characteristics of the A and B whitefly populations with respect to host range, host preferences, and virus-vector capabilities. Here, from tracking data, we provide direct evidence that the A and B whitefly populations existed simultaneously in the state for a short period of time during 1989-90, and that by 1991, the B type population had become predominant whitefly pest and whitefly vector of plant viruses in Arizona crops. Unique host ranges and host preferences represent the most important distinctions between these two populations of B. tabaci, and are largely responsible for the altered epidemiologies of several whitefly- associated virus diseases, and for new pest problems in previously unaffected crops. From these collective data, it is possible to present an historical documentation of the emerging importance of the B whitefly as a pest and virus vector in Arizona. An unusually broad host range and the ability to induce phytotoxic disorders, set the B population apart from the historically problematic, local A type B. tabaci, and provide insights into the underlying basis of its unprecedented impact on crop production in Arizona. Baseline information about whitefly biology, host range, and virus-vector capabilities is relevant to the design and implementation of management practices aimed at controlling the whitefly as a pest and virus vector in Arizona crops.
    • Mixed Lettuce and Romaine Variety Trials 1995/96

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

      Hurlburt, M. W. II; Ray, D. T.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Most lettuce (Lactuca sativa L) seed fails to germinate at high temperatures. This phenomenon thermodormancy, is common in desert regions where 87% of all lettuce is grown in the U.S.A. A study was conducted using a non-thermodormant plant introduction, PI 251245, and two highly thermodormant Dutch butterhead cultivars, 'Dabora' and 'Severa'. Reciprocal crosses were made and germination trials conducted to observe how maternal and paternal influence and seed color contribute to thermodormancy. At 25 °C, germination was 100% for the three parents and the reciprocal F1 hybrids. Germination differences occurred at both 30° and 35 °C among the parents, with P1251245 with 100% germination and Dabora and Severa with less than 10% germination at both temperatures. Segregating F3 and F4 populations from Dabora x PI 251245 were investigated further. Genetic variation found between families suggests that breeding lettuce for improved thermotolerance may be possible. Seed color did not influence thermodormancy.
    • 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.
    • 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.
    • Management of Downy and Powdery Mildew 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)
      Downy and powdery mildew are caused by the plant pathogenic fungi Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development ofdowny mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for management of these diseases in 1996. Both downy and powdery mildew developed in the test plots. All tested materials significantly reduced the severity of downy mildew compared to plants not treated with a fungicide. Compared to nontreated control plants as well as some tested materials and rates, significant reduction of powdery mildew was achieved with Azoxystrobin 80WDG + Latron B-1956, BAS 490 02F, Ciba G /MZ + Mancozeb 75DF, Dithane 75DF + Latron CS-7, Propamocarb 6EC (high rate), R11-7281 2F + Larron CS-7, and Microthiol 80WDG.
    • Postemergence Herbicide Weed Control in Onions

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Onions treated at the 2-leaf stage of growth with the 3rd leaf just beginning to emerge with postemergence herbicides bromoxynil (Buctril®) and oxyfluorfen (Goal®) exhibited slight injury at 11 days after treatment (DAT) but had recovered to show no injury at 1 month after treatment (MAT). Annual yellow sweetclover (Melilotus officinalis) was the predominat weed in the test site and early ratings showed that Goal at 0.25 lb a.i. /A and Goal plus Buctril gave marginally acceptable control at 80 %. Buctril alone did not control clover. At 1 MAT, the clovers had recovered from the initial injury and the level of control had declined to become unacceptable.
    • 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.
    • 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
    • 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.
    • 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.