Further Seed Dressing Trials against Wheat Bulb Fly (Leptohylemyia coarctata (Fall.)) in East Anglia, 1966–68

Abstract

SUMMARY A seed dressing of chlorfenvinphos, ethion or carbophenothion gave good control of wheat bulb fly (Leptohylemyia coarctata (Eall.)) particularly with late drilling, but was less effective with early sowings of winter wheat. The extra insurance of seed dressing against wheat bulb fly for early sowings was worth while where autumn egg numbers were high. “Dursban” (O, O‐diethy10–3, 5, 6‐trichloro‐2‐pyridyl phosphorothioate), formulated as a seed dressing, gave a good kill of larvae but was phytotoxic, particularly on a peaty loam soil.

Chemical Control of Wheat Bulb Fly in the East Midlands, 1968–70

“…Dieldrin seed dressing gave an acceptable control in our East Midland field trial, which contrasts markedly with recent findings in eastern England (Maskell, 1970). Here chlorfenvinphos, either as a powder or liquid dressing, gave better results, irrespective of soil type or drilling date, than dieldrin, with ethion and carbophenothion being better than dieldrin with late or very late drillings respectively.…”

“…Mathias and Roberts (1969) confirmed this damage on a calcareous clay loam (Sherboume series), the large field plots recovering well in the early spring. Maskell (1970) reported phytotoxicity of the same compound on a peaty-loam site in eastern England. In the present study even the special seed dressing formulations of 'Dursban' failed to prevent the marked delay in germination, and this is considered to be too serious a drawback to warrant further study.…”

“…Of the newer commercial dressings the organophosphorus compound chlorfenvinphos seems intermediate between these groups in this respect, so that a useful kill of larvae occurs in the tissues under certain conditions. Maskell (1970) believes that larvae pick up a lethal dose when moving towards the plant through "the zone of protection" afforded by organophosphorus materials, since residues in the bulb can be less than one part per million. This kill, however, occurs best when chlorfenvinphosdressed seed is drilled late in the year so that the interval between drilling and larval mobility and entry is relatively short (4-6 wk).…”

The Use of Insecticidal Seed Dressings as a Means of Decreasing a Population of Wheat Bulh Fly (Leptohylemyia coarctata(Fall.))

“…However, the amount of insecticide remaining on the seed at the time of larval invasion was low, being 4 and 40 per cent of the initial loading for chlorfenvinphos and ethion respectively. These retention figures for insecticidal loadings are very low compared with those obtained by Maskell (1970). It seems likely that because of the greater solubility of chlorfenvinphos (150 p.p.m.)…”

“…These crops, therefore, favour the development of wheat bulb fly populations and provide a substantial reservoir of the pest. It is well known that insecticidal seed dressings are less effective on early-sown than on late-sown wheat (Maskell, 1970), but the large number of flies that comes from this source makes it necessary to consider using insecticides to decrease their numbers.…”