Toxicity and residual effects of spinetoram on adults and larvae of Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae)

Abstract

The use of organophosphate insecticides is one of the main strategies for the chemical control of Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae) in Brazil. Although organophosphate insecticides are effective in population suppression, their constant use (up to 5 applications/harvest) may favor pest resistance. Nevertheless, some organophosphate insecticides are highly toxic to natural enemies and thus their use has been banned. In this study, we investigated acute and residual toxicity of different doses of insecticide spinetoram for the control of larvae and adults of A. fraterculus and C. capitata under laboratory and field conditions. Spinetoram (Delegate 250WG™) showed high toxicity to adults and larvae of A. fraterculus and C. capitata (mortality>80%), based on topical application and ingestion bioassays. At the highest dose evaluated, 5.0 g a.i. (active ingredient) per 100 L of water, spinetoram was statistically similar to organophosphate (Lorbans 480BR™), but superior to neonicotinoid (Eleitto™), standard products for fruit fly control in Brazil. In addition, at doses 3.75 and 5 g a.i.100 L-1, spinetoram showed significant toxicity (mortality>70%) via tarsal contact for both species. Furthermore, toxic effects at depth were observed on larvae of 1st, 2nd, and 3rd instars of fly species in apple and peach fruits, reducing adult emergence by up to 90%. In the field, the highest dose evaluated (spinetoram 5 g a.i.100 L-1) reduced infestation of A. fraterculus by 90%. The results show that spinetoram could be used in the management of A. fraterculus and C. capitata, also as an alternative control for insect resistance management programs.