Crop loss assessment on winter wheat attacked by the grain aphid, Sitobion avenae (F.), 1974–77

SUMMARY Forty‐nine experiments were done during 1974–77 on commercially grown winter wheat crops in England and Wales to investigate the effects on grain yield of feeding on the ear by the grain aphid, Sitobion avenae. The results show that one spray of pirimicarb applied at the beginning of flowering when there were five or more aphids per ear and the number was rising gave an increase in grain yield of approximately 12.5 per cent. Much lower increases were recorded when sprays were applied later than this growth stage or when the number of aphids did not reach the specified level.