Efficacy of rotation programs against western flower thrips, Frankliniella occidentalis, that include entomopathogenic fungi

Western flower thrips (WFT), Frankliniella occidentalis, is an important insect pest causing significant economic losses to greenhouse producers. Insecticides are the primary means of suppressing WFT populations. However, due to resistance development, an alternative strategy is necessary. Therefore, a pest management strategy that integrates insecticides and entomopathogenic organisms (EPO) into rotation programs may reduce selection pressure on WFT populations. The objective of this study was to evaluate insecticide rotation programs that include Beauveria bassiana, Isaria fumosorosea, Metarhizium anisopliae and Chromobacterium subtsugae. Two greenhouse experiments were conducted using chrysanthemum, Dendranthema x morifolium, to compare efficacy of different rotation programs over an eight-week period in suppressing WFT populations. Flowering chrysanthemums were artificially infested with 25 WFT adults. Six rotation treatments were evaluated: 1) insecticides only, 2) through 4) combination of EPO and insecticides, 5) EPO only, and 6) water only. Treatments were applied weekly for eight weeks. Data collected were number of WFT adults captured on yellow sticky cards and a final quality rating of each plant. Results for experiment one indicate there was no evidence for differences between treatment rotations in suppressing WFT populations. However, experiment two resulted in some significant differences among rotations five and six and the rest of the rotations by the end of the 8-week observation period. Furthermore, we found no evidence for differences in quality ratings among rotations for either experiment. Overall, this study does not indicate any apparent efficacy problems with the use of EPO relative to traditional insecticides in greenhouse rotation programs against WFT.