Biological Activity of Bacillus thuringiensis in Drosophila suzukii (Diptera: Drosophilidae)

Whole-culture extracts of Bacillus thuringiensis Berliner strains were assayed against larval and adult Drosophila suzukii (Matsumura), an important invasive pest of many thin-skinned soft fruit crops in North America. Of the 22 serovars tested versus larval D. suzukii , strains of Bacillus thuringiensis var. thuringiensis , kurstaki , thompsoni , bolivia , and pakistani caused high (75 to 100%) first-instar mortalities. Pupal mortality, measured as a failure of adults to emerge, varied with serovar. The first D. suzukii instar was the most susceptible of the three larval instars to B. thuringiensis var. kurstaki HD-1. Larval D. suzukii are shielded from crop treatments, as they develop under the skin of infested fruit, and adults would be a more vulnerable target for an efficacious strain of B. thuringiensis . Only one of the 21 B. thuringiensis serovars, var. thuringiensis , prepared as oral suspensions in sucrose for adult D. suzukii ingestion resulted in significant, albeit low mortality within 7 d. It is not a candidate for use in pest management, as it produces β -exotoxin that is toxic to vertebrates.