The activity and distribution of wheat bulb fly (Delia coarctata) (Diptera:Anthomyiidae) in cereal crops and over fallow land

The flight activity and local distribution of adult D. coarctata were studied on Rothamsted Farm during 1970-5 using several trapping methods. Changes in the activity and distribution of the flies were followed as the population aged, and in females these changes were associated with maturation of their eggs. Most females appeared to stay at their emergence sites in winter wheat until egg-laying started about 1 month later. They then dispersed and both sexes were found in previously uninfested cereals and grass as well as on fallow land where the eggs are laid. Flight occurred chiefly in the late afternoon and evening. The concentration of flies at their emergence sites for several weeks before egg laying could facilitate chemical control, provided the practical difficulties of application can be overcome.