RESUMO
A greenhouse study was conducted to investigate the degradation kinetics of spinosad, flufenoxuron, dimethoate and imidacloprid in tomato (Solanum lycopersicum L.) foliage and their residual toxicity on Engytatus varians (Distant) (Hemiptera: Miridae), a predator of the tomato psyllid Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae). Insecticides were sprayed at 100% and 50% of their maximum field-registered concentrations (MFRC). Starting 6â¯h after spraying, leaf samples were taken every 10â¯d for 40â¯d and analyzed while E. varians adults were exposed to treated leaves to evaluate residual toxicity. Immediately after application at 100% MFRC, the residue concentrations were 73.34⯵gâ¯g-1 spinosyn A and 59.2⯵gâ¯g-1 spinosyn D, 9.21⯵gâ¯g-1 flufenoxuron, 71.49⯵gâ¯g-1 dimethoate and 31.74⯵gâ¯g-1 imidacloprid. At 50% MFRC, initial residue concentrations were between 75% and 90% those at 100% MFRC. The estimated half-life (DT50) of spinosyns A and D, flufenoxuron, and dimethoate was between 34 and 40â¯d, while that of imidacloprid was 112â¯d. Flufenoxuron caused no mortality, while mortality due to spinosad was less than 10%, and only during the first 10â¯d. Mortality caused by either imidacloprid or dimethoate was around 100% up to 10â¯d after application, then decreased to around 30% after 40â¯d. Dimethoate toxicity was approximately proportional to residue concentration, while for imidacloprid there was an apparent threshold around 15⯵gâ¯g-1. These results can be used to establish periods harmless for release of E. varians in the control of B. cockerelli on tomato crops under greenhouse conditions.