Chemical control of wheat bulb fly (Delia coarctata) attacking winter wheat in Eastern England, 1969–1981

Abstract

SUMMARYSeveral insecticides were applied to the soil and/or plant foliage as granule or spray treatments to control wheat bulb fly larval damage to late‐sown winter wheat in eastern England between 1969 and 1981. Treatment effects in preventing larvae from entering plants or in killing larvae within attacked shoots and effects on yield were compared with controls and with a standard chlorfenvinphos seed treatment.Granules of chlorfenvinphos, fonofos or terbufos at rates between 1–40 and 2–24 kg a.i./ha were highly effective when applied at sowing in mineral soils, and fonofos granules were also effective in organic soils. Single spray applications of chlorfenvinphos, and especially of fonofos, applied at sowing at rates between 0–84 and 1–40 kg a.i./ha were effective in both soil types.Sprays applied when wheat bulb fly eggs began to hatch were more effective in mineral than in organic soils and gave lower yield increments than the standard chlorfenvinphos seed treatment.Single sprays of chlorpyrifos, formothion, omethoate or pirimiphos‐methyl, applied to the foliage when larval damage was first seen (‘deadheart’ stage) significantly increased yields; dimethoate spray or granule treatments applied at this stage were not significantly better than control and ‘deadheart’ treatments were generally less effective than chlorfenvinphos seed treatment.Multiple treatments involving two or more of the above methods were extremely effective in both soil types; their economic and environmental implications are discussed.