Evaluation of insecticides for curative, preventive, and rotational use on Scirtothrips dorsalis South Asia 1 (Thysanoptera: Thripidae)

The chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), is a cryptic species complex of at least 9 distinct species, 2 (South Asia 1 and East Asia 1) of which exist in the USA. To integrate chemical insecticides and mycoinsecticides into the preventive and curative tactics used for S. dorsalis, we evaluated 10 older and newer chemical insecticides and 3 mycoinsecticides against S. dorsalis South Asia 1, a dominant member of the species complex in the USA. An insecticide was considered effective when it induced greater than 70% mortality of larvae or adults. The older insecticides (acetamiprid, clothianidin, thiamethoxam [foliar application], and imidacloprid [drench application]) were found to be efficacious in reducing S. dorsalis populations in both curative and preventive situations (>= 7 d after treatment). Among insecticides with newer chemistries, foliar application of spinetoram, cyantraniliprole, tolfenpyrad, and formulations of chlorantraniliprole + thiamethoxam were effective for both preventive and curative control (>= 10 d after treatment). Among mycoinsecticides, Isaria fumosorosea Wize (Cordycipitaceae) was effective in suppressing thrips curatively (>= 10 d after treatment). In the insecticide rotation field trial, effectiveness of a Chenopodium (Amaranthaceae) extract and 3 mycoinsecticides alternated with spinetoram was comparable to spinetoram treatment alone. Because S. dorsalis South Asia 1 is a serious pest of several economically important crops in many counties of Florida and Texas, and an emerging pest in California, this study is important in providing information to vegetable and ornamental plant growers regarding effective insecticides with different modes of action that can be rotated to suppress S. dorsalis, and delay the evolution of insecticide resistance. The results also suggest retention of effective products for an extended period in the marketplace.