• Preemergence Herbicides for Weed Control in Melons

      Umeda, K.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      All herbicide treatments, Prefar, Frontier, Dual Magnum, Valor, and Prefar combined with Dual Magnum or Frontier caused less than 10% injury on cantaloupes. Frontier at 0.75 lb AI/A, Dual Magnum at 1.0 lb AI/A, Valor at 0.03 and 0.05 lb AI/A controlled weeds similar to Prefar. Prefar at 4.0 lb AI/A combined with Frontier controlled tumble pigweed (94%), narrowleaf lambsquarters (95%), Wright’s groundcherry (97%), and horse purslane (94%). None of the preemergence herbicide treatments controlled purple nutsedge.
    • Reaction of Different Cultivars of Lettuce to Development of Powdery Mildew on Lettuce in 2001

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Seven different cultivars of lettuce were seeded and watered on Dec 1, 2000 at the Yuma Valley Agricultural Center. Cultivars were rated for severity of powdery mildew caused by Erysiphe cichoracearum at plant maturity (Mar 21). The highest levels of powdery mildew were found on the cultivars Winterhaven and Silverado, whereas lower disease severity was observed on Jackel, Cibola, RC-74 and Accolade. All tested cultivars would have required application of fungicides to reduce the amount of powdery mildew to acceptable levels. On the other hand, planting of lettuce cultivars with some disease tolerance may require less fungicide inputs to achieve acceptable disease control compared to planting susceptible cultivars.
    • Residual Efficacy and Field Performance of Thiacloprid (Calypso) Against Whiteflies in Melons

      Palumbo, John C.; Reyes, F. J.; Mullis, C. H. Jr.; Amaya, A.; Ledesma, L.; Carey, L.; Byrne, David N.; Baciewicz, Patti; Department of Entomology, Yuma Valley Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies were conducted to compare the residual field efficacy of Calypso, compared with soil applications of Admire and foliar sprays of Provado and Actara. The results demonstrate that several insecticide product uses are being developed that offer melon growers management alternatives for controlling whiteflies comparable to what they have experienced with Admire. Calypso showed excellent promise as a foliar, post-planting spray with good residual activity. Two spray applications provided good whitefly control and excellent crop and melon quality. Although we saw a measurable impact on some natural enemies, the compound is supposedly very safe to honeybees. Overall, when directed at low adult and immature densities, Calypso provided 14-21 days of residual control and was capable of preventing yield and quality losses in spring melons. These studies also emphasize, that like the IGRs, these foliar neonicotinoids should be used when whiteflies densities are low and beginning to build. This compound may be available as early as 2002.
    • Safety of New Preemergence Herbicides on Lettuce and Broccoli

      Umeda, K.; Lund, N.; MacNeil, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Carfentrazone at 0.0125 and 0.025 lb AI/A was safe on all three lettuce cultivars. No stand reduction was observed. Sulfentrazone confirmed the initial screening test rate range of 0.05 to 0.1 lb AI/A for demonstrating marginal lettuce safety. Flumetsulam and thifensulfuron showed greater selectivity only in head lettuce while severely injuring romaine and red leaf lettuce. Rimsulfuron caused considerable stand reduction of all three lettuce cultivars. Sulfentrazone, fluroxypyr, and thifensulfuron exhibited good tolerance on broccoli as no stunting or stand reduction was observed at maturity.
    • Sustaining Arizona's Fragile Success in Whitefly Resistance Management

      Li, Andrew Y.-S.; Dennehy, Timothy J.; Li, Sarah X.-H.; Wigert, Monika E.; Zaborac, Marni; Nichols, R. L.; Byrne, David N.; Baciewicz, Patti; Cotton Incorporated, Cary, North Carolina (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Arizona cotton experienced a severe crisis in 1995 stemming from resistance of whiteflies to synergized pyrethroid insecticides. The insect growth regulators (IGRs), Knack® (pyriproxyfen) and Applaud® (buprofezin), served a pivotal role in resolving this problem. Similarly, Admire® (imidacloprid), the first neonicotinoid insecticide to obtain registration in Arizona, has been the foundation of whitefly control in vegetables and melons. In this paper we provide an update regarding the susceptibility to key insecticides of whiteflies from Arizona cotton, melons, and greenhouses. Overall, whitefly control in Arizona cotton remained excellent in the 2000 season and there were no reported field failures. However, there was a significant decrease in susceptibility to Applaud of whiteflies collected from cotton. One collection from Eloy, Arizona, in 2000 had susceptibility to Applaud that was reduced 129-fold relative to a reference strain. Whiteflies resistant to Knack, detected for the first time in Arizona in 1999, were again detected in 2000 but at lower frequencies than in 1999. Though whiteflies resistant to Admire/Provado® continued to be found at specific locations, overall susceptibility to Admire/Provado in 2000 remained high in whitefly collections from cotton. The new neonicotinoid insecticides, thiamethoxam and acetamiprid, were similar in toxicity to Arizona whiteflies in laboratory bioassays and we confirmed the significant but relatively low-order cross-resistance we previously reported between these neonicotinoids and Admire/Provado. Arizona whiteflies continued to be relatively susceptible to mixtures of Danitol® (fenpropathrin) and Orthene® (acephate). Factors that could undermine the current success of whitefly resistance management in Arizona are discussed. These include: 1) more severe resistance to IGRs in whiteflies from cotton, stemming from increased IGR use within and outside of cotton; 2) resistance of vegetable, melon and greenhouse whiteflies to the various formulations of imidacloprid (Admire, Provado, Merit®, Marathon®); 3) the imminent registration of new neonicotinoid active ingredients in cotton, greenhouses and other Arizona crops.
    • Timing Kerb Applications in Lettuce

      Tickes, B.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Kerb (Pronamide) is often ineffective when it is leached below germinating weed seeds with sprinkler irrigation. Efficacy can be improved by making delayed aerial applications after the sprinklers have been started and before weeds have become established. Tests were conducted to determine the optimal time of application. Optimal times varied with the season and ranged from two to three days after the sprinklers had started during the early season (Sept.) to five to six days during the late season (January).
    • Timing of Glyphosate Application for Weed Control in Glyphosate Tolerant Lettuce

      Umeda, K.; Hicks, T. V.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies were conducted to determine the optimum time to apply glyphosate to glyphosate-tolerant Lactuca sativa cv. Raider (head lettuce). The study was initiated near Yuma, Arizona in September 2000. Single applications of glyphosate at 1.0 lb AI/A were made to head lettuce at development stages of 2, 4, 6 and 8 leaves. Glyphosate treatments did not injure lettuce. A single application at the 2 or 4 leaf stage was optimal for near complete control of Portulaca oleracea (common purslane), Chenopodium murale (nettleleaf goosefoot), Malva parviflora (cheeseweed), and Leptochloa spp. (sprangletop). Later applications at the 6 or 8 leaf stages allowed weeds, especially, common purslane to compete with the crop. Treatments applied at the 2 or 4 leaf stages required the least amount of time to hand weed and resulted in highest fresh weight yields.