The Effects of Known Amounts of γ‐BHC and Organophosphorus Seed Dressings on Growth of Wheat Seedlings and on Attack by Larvae of Wheat Bulb Fly (Leptohylemyia coarctata (Fall.))

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Abstract
SUMMARY: Six trials were done during three years (1966–69) in eastern England to study how known amounts of insecticidal seed dressings affect the growth of winter wheat and the severity of attack by wheat bulb fly larvae. In the first two years γ‐BHC dry dressing was applied to seeds previously treated with a liquid organomercury fungicide, but in the third year seeds were dressed with powders containing fungicide mixed with the insecticides γ‐BHC, chlorfenvinphos or ethion. Analysis using gas liquid chromatography showed that the ethion+ fungicide dressing stuck to the seeds much better than the chlorfenvinphos+fungicide dressing or either formulation of γ‐BHC. Some ethion, γ‐BHC and chlorfenvinphos later fell off the seeds, the exact amount depending on the method of drilling. Small amounts of insecticide, less than about 10μg/seed of γ‐BHC or less than about 15μg/seed of the organophosphorus compounds, were ineffective against wheat bulb fly. Increasing amounts of all three insecticides progressively decreased the percentage of damaged shoots and the percentage of plants with live larvae, but more of the organophosphorus insecticides, especially of ethion, was generally needed to give the same protection as γ‐BHC. No seed treatment damaged seedlings in trials on peaty loams or sandy clay loams, but seeds dressed with the standard amount of liquid organomercury fungicide and several different amounts of γ‐BHC dry dressing germinated poorly in the sandy loam soils.

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