POPULATION-DYNAMICS OF APHIDS AND SYRPHID LARVAE IN WINTER-WHEAT TREATED WITH DIFFERENT RATES OF PIRIMICARB

The effects of different rates of pirimicarb on aphids and syrphid lar vae in winter wheat were studied from 1991 to 1993. The numbers of aph ids and pre-imaginal stages of aphid-specific predators were determine d visually in four replicated randomised plots. The years showed stron g differences in aphid infestation, syrphid migration and oviposition, and larval density probably because of different weather conditions. The results indicate high efficacy of pirimicarb to aphids but also to syrphid larvae at the currently recommended rate (100 g a.i. ha(-1)) and even at 50 g a.i. ha(-1). A certain degree of selectivity was obta ined at 25 g a.i. ha(-1).