27 November 1998

Aphid forecasts eased

PEAKS and troughs in wheat aphid numbers every four years since the early 1980s have been identified by ADAS and should make the prediction of infestation levels easier and enable better spray decisions in future.

ADAS surveys also show that in years of high aphid incidence, notably 1984, 88 and 95, there were lower than average levels of predators and parasitoids. But the year after the peaks high numbers of some of the pests natural enemies occurred and decimated the pest during and just after flowering.

Numerous trials have also shown that in non-peak years it is often possible to control the pest with one-third rate aphicides applied when the spray threshold occurs, provided there are reasonable numbers of predators and parasitoids around.