Some effects of polyphagous predators on an outbreak of cereal aphid (Sitobion avenae F.) and orange wheat blossom midge (Sitodoplosis mosellana Géhin).

Abstract

The effect of polyphagous predators on the abundance of grain aphids, Sitobion awenae, and orange wheat blossom midge, Sitodoplosis mosellana, was examined in crops farmed using the conventional farm practice (CFP) compared with that using an integrated farming system (IFS), The effect of these pests on wheat grain yield and quality was also examined. Predator exclusion reduced the total polyphagous predator activity by up to 85% compared with control areas. However, no difference was found in the number of grain aphids between the control areas and where numbers of polyphagous predators had been reduced, Nor was there a difference in the number of grain aphids between the two farming systems. The late aphid infestation, between GS69-77, caused no reduction in grain dry weight. Numbers of midge larvae per ear were the same in control and enclosed areas where polyphagous predators had been reduced, but were 17% lower in the IFS compared with CFP plots, Up to 12 midge larvae per ear had no significant impact on grain dry weight. There was a trend towards poorer grain quality in enclosed areas