Chemical control of onion fly, Delia antiqua

In nine trials done in 1972-4 seed treatments reduced attacks of onion fly larvae very effectively and most of the organophosphorus formulations gave protection up to harvest, 12–17 wk after sowing. Pirimiphos-ethyl and isofen-phos each at 10 or 20 g a.i./kg seed controlled onion fly larvae well and they were not seriously phytotoxic in any of the trials. Chlorpyrifos, trichloronate, ethion, iodofenphos, chlorfenvinphos wettable powder or triazophos all at iog a.i./kg seed were also effective, but they were tested in fewer trials. Diazinon at 10 or 20 g a.i./kg seed, carbophenothion and chlorfenvinphos liquid seed dressing at 10 g a.i./kg seed controlled onion fly well, but in some trials they were phytotoxic; methiocarb, mecarphon and oxamyl were much less effective. At 1–12 kg a.i./ha chlorfenvinphos granules applied over the rows shortly before the attack was expected was the best granular formulation, but it was not as effective as the better seed treatments.