Citrus Thrips (Thysanoptera: Thripidae) Pesticide Resistance in the Coachella and San Joaquin Valleys of California

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Abstract
Citrus thrips (Scirtothrips citri (Moulton)) resistance to dimethoate, or formetanate, or both was evaluated in 13 commercial citrus groves in the Coachella and San Joaquin Valleys of California in 1986. Dimethoate resistance was apparent at one site in the Coachella Valley (30.0-fold at the LC50) and at all San Joaquin Valley sites (21.5–90.3-fold at the LC50). Increased levels of formetanate use appeared to be correlated with increased resistance (up to 31.0-fold at the LC50) to this chemical. Intensity and frequency of dimethoate and formetanate resistance were higher and more widespread in the San Joaquin Valley than in the Coachella Valley. These results are discussed with respect to general patterns of citrus thrips resistance and their implications to resistance management.