Residual Toxicity of Abamectin, Chlorpyrifos, Cyromazine, Indoxacarb and Spinosad on Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) in Greenhouse Conditions

Liriomyza trifolii is an important pest of vegetable crops in many parts of the worldincluding Iran. In this study potted bean plants were sprayed with recommended fieldrates of abamectin, chlorpyrifos, cyromazine, indoxacarb and spinosad. To assess the residualactivities of these insecticides, the plants were infested with L. trifolii adults 2 hours; 1, 3,5, 7, 10, 15, 20, 25 and 35 days after insecticidal treatments. The adults were allowed to stayon treated plants for eight hours. The treated plants were kept in a greenhouse. Numberof feeding stipples and larval mines on leaves, as well as pupation and adult eclosion rateswere assessed. Two-way ANOVA procedure of SAS was used for statistical analysis andthe treatment means were separated using Duncan’s multiple range test. Abamectin andspinosad severely affected egg hatching and embryonic development. Eggs oviposited inleaves with residues of chlorpyrifos up to 5 days old, had reduced hatching. Larval developmentwas also, affected by residues of chlorpyrifos up to four weeks old. Indoxacarbreduced larval development and adult eclosion in treatments with up to 20 days old residues.Cyromazine had no effect on the number of larval mines, but, pupation was severelyhampered and adult eclosion was completely ceased even in treatments with five weeksold residues. Determining the residual activity of insecticides used for controlling this pestis useful in avoiding unnecessary treatments.