• Biotype Designations and Insecticide Susceptibility of Southwestern Bemisia tabaci

      Dennehy, Timothy J.; DeGain, Benjamin A.; Harpold, Virginia S.; Nichols, Robert J.; Byrne, David N.; The University of Arizona. Tucson, AZ; Cotton Incorporated, Cary, NC (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      We report biotype identifications and susceptibility to insecticides of whiteflies (Bemisia tabaci) collected from cotton, vegetables, melons and ornamental plans during the 2005 season. No major problems with field performance of insecticides against whiteflies were confirmed in 2005 in Arizona. Whitefly resistance to pyriproxyfen did not increase, relative to levels recorded in 2004. However, we detected pyriproxyfen resistance in all Arizona whitefly samples tested. A single sample collected from cotton in Holtville, CA, had no detectable resistance to pyriproxyfen. Samples from cotton in Buckeye, Coolidge, Scottsdale, and Stanfield, Arizona had the highest levels of resistance, with > 31-45% of eggs surviving diagnostic concentration bioassays of 0.1 ug/ml pyriproxyfen. Whitefly susceptibility to buprofezin (Applaud®/Courier®) has not changed significantly since 1997. Resistance to synergized pyrethroids (e.g., Danitol® + Orthene®) has decreased strikingly on a statewide basis since 1995, though unacceptably high frequencies of resistant whiteflies were detected in some 2005 collections from all commodities sampled. Whiteflies collected from Arizona cotton, melons, and vegetables continued to be highly susceptible to imidacloprid (Admire®/Provado®). One whitefly collection from poinsettias in Phoenix (05-39) was substantially less susceptibile to imidacloprid, and the related neonicotinoid insecticides, acetamiprid, and thiamethoxam. Regression analysis yielded a significant correlation for whitefly susceptibility to acetamiprid and thiamethoxam. Whiteflies from cotton that were least susceptibile to acetamiprid were also significantly less susceptible to thiamethoxam (Actara®/Centric®/Platinum®). The most worrisome of our 2005 findings was that 6 out of 13 samples of whitefly-infested poinsettias collected from retail stores in metropolitan Tucson and Phoenix consisted of only the Q biotype of Bemisia tabaci. The plants were infested with very low whitefly numbers and thus we were unable to establish them in laboratory cultures to evaluate their resistance status. The Q biotype is native to Spain and was first detected in the US by our group in 2004 on a sample taken from poinsettias. The Q biotype strain we detected in 2004 was highly resistant to a broad range of insecticides used to manage whiteflies in Arizona. None of the 26 field collections evaluated in 2005 was the Q biotype.
    • Comparative Efficacy of Insecticide Combinations Against Whitefly Adults in Melons

      Palumbo, John; Byrne, David N.; University of Arizona, Yuma Arizona (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      Several large plot field studies were conducted in the spring of 2006 and 2007 to evaluate and compare the efficacy of several insecticides (used alone and in combinations) for knockdown and residual control of adult whiteflies in cantaloupes. Treatments were initiated when adult whitefly populations exceeded action threshold of 2 adults/ leaf. Evaluations of adult and immature control were made a various intervals following each application. The results of this study demonstrate that the synergized pyrethroid still provides the most significant knockdown activity on whitefly adults among registered alternatives in melons. In most cases, the addition of endosulfan (Thionex) with bifenthrinin provided 7-14 days of adult suppression below the action threshold. Residual control of adults was less effective following a second sequential application. Other alternative tank-mix partners with Capture were less effective, but might be useful to use in rotation with the Capture+Thionex treatments to provide adult knockdown. As we anticipated, adult and immature whitefly control did not differ among the bifenthrin formulations (Capture vs. generics). Finally, because of the risk of whitefly resistance and the heavy reliance on pyrethoids in all vegetable crops grown in the desert, new alternatives for adult whitefly control are needed.
    • Efficacy of RADIANT (Spinetoram) Against Western Flower Thrips in Romaine Lettuce

      Palumbo, John; Richardson, Jesse; Byrne, David N.; University of Arizona, Yuma Arizona; Dow AgroSciences, Hesperia, CA (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      RADIANT, a new 2nd generation spinosyn insecticide has recently been introduced to the vegetable industry that has shown excellent activity against western flower thrips in lettuce. Several studies were conducted over 2 growing seasons at the Yuma Ag Center to evaluate the efficacy of RADIANT against thrips in romaine lettuce. Three trials were conducted in spring lettuce under moderate and heavy population pressure, and two fall trials were conducted under low to moderate thrips pressure. In each study, RADIANT performed statistically comparable to or better than Success for control of thrips, but at lower use rates. It appears to provide better residual activity against larvae than Success and the standard compounds presently used, but does not appear to provide any additional adult efficacy. RADIANT will be an excellent addition to our IPM programs, however because it has the same mode-of-action as Success, it will not provide an additional rotational partner for our resistance management programs.
    • Have Distances Traveled by the Sweet Potato Whitefly Been Underestimated?

      Byrne, David N.; Hardin, Jesse A.; Byrne, David N. (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      The importance of the sweet potato whitefly to Arizona vegetable continues to ebb and flow from year to year. Over the last 25 years much of this likely is tied to the invasion by different strains. As we continue to study this insect, an aspect of importance to their management is their ability to disperse. In past studies we have determined how far they are capable of flying in a day’s time, 95% migrate 1.6 miles. We are now investigating their ability to fly multiple days. If they do migrate on more than 1 day, we must readjust our estimates of their influence on surrounding fields.
    • Insect Crop Losses and Insecticide Usage for Head Lettuce in Arizona: 2006/2007

      Palumbo, John; Nolte, Kurt; Fournier, Al; Ellsworth, Peter; Byrne, David N. (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      Impact assessment is central to the evolution and evaluation of our local Insect Pest Management (IPM) programs. Quantifiable metrics on insecticide use patterns, costs, targets, and frequency, crop losses due to all stressors of yield and quality, and other real world economic data (e.g., crop value) are our most objective tools for assessing change in our systems. We recently initiated a project to measure the impact of insect losses and insecticide uses in head lettuce grown in Yuma, AZ and the Bard-Winterhaven area of Imperial County, CA. The data generated in this report is useful for responding to pesticide information requests generated by EPA, and can provide a basis for regulatory processes such as Section 18 requests, as well as for evaluating the impact of our extension programs on risk reduction to growers. This information also confirms the value of PCAs to the lettuce industry by showing the importance of cost-effective management of insect pests in desert lettuce production.
    • Insect Crop Losses and Insecticide Usage for Spring Melons in Central Arizona for 2007

      Palumbo, John; Fournier, Al; Ellsworth, Peter; Taylor, Erin; Rice, Kevin; Byrne, David N. (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      Impact assessment is central to the evolution and evaluation of our IPM programs. Quantifiable metrics on insecticide use patterns, costs, targets, and frequency, crop losses due to all stressors of yield and quality, and other real world economic data (e.g., crop value) are our most objective tools for assessing change in our systems. We recently initiated a project to measure the impact of insect losses and insecticide uses in cantaloupes and watermelons grown in central Arizona (Maricopa, Pinal and La Paz counties). The data generated in this report is useful for responding to pesticide information requests generated by EPA, and can provide a basis for regulatory processes such as Section 18 or 24c requests, as well as for evaluating the impact of our extension programs on risk reduction to growers. This information also confirms the value of PCAs to the melon industry by showing the importance of cost-effective management of insect pests in desert production.
    • Insect Crop Losses and Insecticide Usage for Spring Melons in Southwestern Arizona for 2007

      Palumbo, John; Nolte, Kurt; Fournier, Al; Ellsworth, Peter; Byrne, David N. (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008-01)
      Impact assessment is central to the evolution and evaluation of our IPM programs. Quantifiable metrics on insecticide use patterns, costs, targets, and frequency, crop losses due to all stressors of yield and quality, and other real world economic data (e.g., crop value) are our most objective tools for assessing change in our systems. We recently initiated a project to measure the impact of insect losses and insecticide uses in cantaloupes and watermelons grown in Yuma, AZ and the Bard-Winterhaven area of Imperial County, CA. The data generated in this report is useful for responding to pesticide information requests generated by EPA, and can provide a basis for regulatory processes such as Section 18 or 24c requests, as well as for evaluating the impact of our extension programs on risk reduction to growers. This information also confirms the value of PCAs to the melon industry by showing the importance of cost-effective management of insect pests in desert production.