Gamma BHC, aldrin, dieldrin, endrin, DDT and parathion have been tested as seed dressings in field experiments for the control of wheat bulb fly, Leptohylemyia coarctata (Fall.), in eastern England. The concentrations ranged from 20 to 70 per cent, and the dressings were applied at 2–3 oz./bushel.
At concentrations of 40 per cent, or over, the first three materials appreciably reduced attack and at high infestations increased yield; within the period October to January their effectiveness increased the later the wheat was sown. There was evidence that they were less effective on highly organic soils. The other materials were either less effective or had other disadvantages.
Seed dressings of γ BHC usually reduced the number of larvae entering the plant but had little effect on larvae which succeeded in entering. Aldrin and dieldrin and probably most other materials usually had less effect on the entry of larvae but were very effective in killing larvae after entry so that the plant could subsequently recover.
Combine-drilling of aldrin or dieldrin affected the larvae in the same way as seed dressings; in one season on a peaty soil seed dressings were more effective than combine-drilling, but in another season on a mineral soil seed dressings were slightly less effective than combine-drilling. However, it was clear that with combine-drilling very much higher quantities of insecticide per acre were needed to achieve a comparable result. Both aldrin and dieldrin gave similar results.