To find out if it were possible to reduce wireworm populations by means of seed dressings which are convenient to use, and desirable in other ways, the direct and residual effects of insecticides on wireworms (Agriotes spp.) attacking spring-sown and winter-sown wheat were tested on a clay soil at Rothamsted, Hertfordshire. Treatments comprised dressing seed with dusts containing 20% (standard) and 60% (high-rate) γ-BHC and 40% (standard) dieldrin, all at 2 oz. per bushel, 60% dieldrin at 70 oz. per bushel (high-rate), or a liquid containing 30% dieldrin at 1 fl. oz. per bushel; combine-drilling 0.5% γ-BHC dust at 1 cwt. per acre with the seed; and spraying the soil surface after sowing with 1 gal. 30% aldrin in 40 gal. water per acre. The high-rate BHC and dieldrin seed dressings, the combine-drilled BHC dust and the aldrin spray significantly reduced wireworm populations when applied to spring- or winter-sown wheat, the reduction in the former case being apparent two years later in one experiment; these reductions were, in general, reflected in increased yields. The standard seed dressings tended to be less effective. Similar results were obtained in an experiment on a fen peat soil in Lincolnshire.

Tests done in one experiment on plots sown with dieldrin-dressed seed showed no evidence that birds grub up plants or seeds that would otherwise have germinated.