The efficacies of cypermethrin, deltamethrin, permethrin, endosulfan, methoxychlor, carbofuran, chlorpyrifos, dimethoate, and malathion were evaluated against the wheat midge, Sitodiplosis mosellana (Géhin). Methods are described for evaluating damage and protection in individually collected wheat heads and whole plants. Weighted values from whole plants provided the best indication of kernel protection and yield response.
Whole plants contained three main types of wheat heads (primary heads, first tillers, and second tillers) which differed in their frequencies, kernel numbers, and developmental times. The latter indicated that the chronology of midge attack, status of midge infestations during spraying, and spray coverage also differed in the head types.
Insecticides provided different levels of kernel protection within and among the various head types. The majority of primary heads emerged before spraying and harbored midge eggs at spraying. In these wheat heads, chlorpyrifos, endosulfan, and malathion provided significantly better kernel protection (60–75%) than permethrin, deltamethrin, and cypermethrin (<7%). The results suggested that the more effective kernel protectants permeated the spikelet and controlled the eggs and/or newly hatched larvae. Kernel protection in the primary heads was closely related to insecticide volatility. Conditions were different in most first tillers and second tillers which emerged after spraying. In these wheat heads, poor spray coverage and short residual activity against adult midge appeared to limit kernel protection by all insecticides.