With the impending loss of the endosulfan registration on melons (July 2012), PCAs are faced with the difficult challenge in managing whiteflies and CYSDV on fall melons. Since the early 1990s, the synergized pyrethroids (e.g., Brigade+Thionex) have been the most efficacious insecticide treatments for control of adult whiteflies. Either insecticide product applied alone often provides only marginal adult activity, but when combined, the mixture consistently provides enhanced efficacy. This activity is a result of one insecticide active ingredient (endosulfan) interfering with the metabolic detoxification of another insecticide (bifenthrin) at its site of action in the insects nervous system. Thus, these pyrethroid tank-mixtures are effective because of the synergistic effects of certain organophosphate, carbamate, and organochlorine insecticides that bind to the active site associated with esterase enzymes responsible for detoxification of pyrethroid insecticides. Over the past several years we have been evaluating a number of OPs and carbamates as tank mix partners to be used as synergists for pyrethroids for adult whitefly control. A study just completed at the Yuma Ag Center compared several OPs, carbamates and other chemistries as synergists with pyrethroids in spring melons. The results were consistent with previous studies and showed that among the OP / Carbamate + Brigade mixtures, only Diazinon (labeled for use on Honeydews only) provided consistent adult efficacy, often comparable to Thionex+Brigade. The other OP/Carbamate mixtures evaluated in the trial were less consistent and rarely provided activity comparabale to Thionex. A new formulation of Agri-Mek SC was also evaluated, but did not consistently provide efficacy comparable to Diazinon or Thionex. Finally, Assail 30SG (applied at the high label rate) provided consistent knockdown and residual control of adults comparable to Thionex following each application. The complete results of this study can be found at: Evaluation of Insecticide Tank-Mixtures as Alternatives to Endosulfan for Control of Sweetpotato Whiteflies in Spring Melons, 2012.

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To contact John Palumbo go to: jpalumbo@ag.arizona.edu

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.