Can spinosad be effective for the integrated management of Anastrepha ludens (Tephritidae) in soil and fallen fruit, and be compatible with the parasitoid Diachasmimorpha longicaudata (Braconidae)?

Tephritid fruit flies are susceptible to insecticide treatments when leaving infested fruit to pupate in the soil and when emerging as adults. Laboratory experiments involved placing third instar larvae of the Mexican fruit fly, Anastrepha ludens on sand treated with the naturally-derived insecticide spinosad (SpinTor 12SC). Negative correlations were detected between the concentration of spinosad and pupation and adult emergence. Treatment of pupae significantly reduced adult longevity, which could impact pest reproduction as adult flies require approximately two weeks to reach sexual maturity. Brief immersion of naturally infested oranges in 33–66 ppm spinosad solution also significantly reduced adult emergence. Exposure to spinosad-treated sand (33 ppm) did not adversely affect the foraging behavior or mortality of the braconid parasitoid Diachasmimorpha longicaudata . We conclude that effective control of A. ludens in soil with spinosad is possible but will likely require application of high concentrations of the insecticide, which may not be economically viable under conventional fruit production schemes. In the case of organic orchards surrounded by wild hosts that harbor large fly populations, targeted spinosad soil applications might be desirable as fly numbers could be significantly reduced without harming parasitoids.