Development of Pesticide-Treated Spheres for Controlling Apple Maggot Flies (Diptera: Tephritidae): Pesticides and Residue-Extending Agents

Abstract

Dimethoate, azinphosmethyl, methomyl, tralomethrin, malathion, fenvalerate, and carbaryl were evaluated in the laboratory for contact toxicity to apple maggot flies, Rhagoletis pomonella (Walsh), with or without a feeding stimulant (sucrose) during a 10-min exposure period. Addition of sucrose decreased LC50s and LC90s of all insecticides tested but had no effect on toxicity relationships among insecticides. In combination with sucrose, dimethoate was most toxic; azinphosmethyl, tralomethrin, and methomyl were more toxic than malathion and fenvalerate; and carbaryl was least toxic. At a concentration of insecticide equal to five times the LC90value established in laboratory tests, all insecticides tested in field cages, except dimethoate and malathion, reduced the duration of fly visitation and feeding on sucrosecoated, insecticide-treated red spheres. Spheres treated with a mixture containing 1.05% (AI) dimethoate or methomyl, 58.95% com syrup, and 40% latex paint as a residue-extending agent killed 76-87%, and 50-62%, respectively, of alighting flies at 0 residual days (before exposure to weather). However, the spheres were ineffective after exposure to 6.6 mm rainfall. Effectiveness of pesticide-treated spheres in killing visiting flies was limited more by loss of feeding stimulant as a result of wash off by rainfall than by degradation of insecticide. Retreating weather-exposed (up to 35 d) dimethoate-treated spheres with 16% sucrose restored effectiveness in killing alighting flies. Neither dimethoate nor methomyl in combination with latex paint and com syrup had a negative effect on the attraction of flies to treated spheres.