The effect of augmenting grain aphid (Sitobion avenae) numbers in a field of winter wheat in spring on the aphid's abundance in summer and its relevance to the forecasting of outbreaks

Publisher Website
Google Scholar
Abstract
Summary: Sitobion avenaewas introduced into areas within a field of winter wheat in Norfolk in mid‐May 1985, when the indigenous population was negligible. Aphid numbers in these areas increased for the first 3 wk and declined for the next 4. A secondS. avenueintroduction into the same areas and into previously uninfested areas was carried out 5 wk after the first introduction, when the crop was at ear emergence complete (G.S. 59). This increased aphid numbers in the previously uninfested areas, but numbers in the previously infested areas continued to decline to below the level in control areas during the subsequent 2 wk. Populations in all areas then increased rapidly to a maximum, followed by a rapid final decline. Monitoring of the aphid and natural enemy populations, and caging aphids onto the crop, revealed that the principal cause of the population decline around G.S. 59 was predation by syrphids. The relevance of these findings to the problem of forecastingS. avenaeoutbreaks is discussed, and a general explanation for cereal aphid outbreaks is put forward.