Activity of Cyromazine on Onion Maggot Larvae (Diptera: Anthomyiidae) in the Soil

Abstract

A laboratory bioassay technique with soil was developed to investigate the toxicity and activity of the insect growth regulator, cyromazine, to onion maggot larvae, Delia antique (Meigen) (Diptera: Anthomyiidae). LC50’s (ppm in soil) for chlorpyrifos, fonofos, and cyromazine were 8.4, 9.4, and 17.5, respectively. Significant mortality due to cyromazine treatment was observed at the time of molt between first and second instar (72 h). Surviving larvae in soil treated with cyromazine developed more slowly than larvae in untreated soil. At 144 h, > 90% mortality occurred in the cyromazine treated soil compared with <10% in untreated soil. Because it has a different mode of action than the currently registered insecticides, cyromazine may have potential as a management tool for resistant populations, or in a resistance management program. Cyromazine may also be effective in controlling other soil insects.