Comparison of a Canadian and a Dutch strain of the parasitoid Aphelinus mali (Hald) (Hym., Aphelinidae) for control of woolly apple aphid Eriosoma lanigerum (Haussmann) (Hom,, Aphididae) in the Netherlands: a simulation approach

Woolly apple aphid, Eriosoma lanigerum is one of the important apple pests in the Netherlands. Weather conditions and natural enemies determine whethe r woolly apple aphid (WAA) will reach pest status. WAA may escape control b y natural enemies and therefore it must be controlled using chemical insect icides. To pl event unnecessary applications of insecticides and to promote biological and natural control of WAA more knowledge is needed about the r ole of natural enemies, weather and their effects on the development of WAA populations, The monophagous parasitoid Aphelinus mali (Hald.) has been in troduced into most of apple growing areas to control WAA, but success is va riable and depends on climatological conditions. In the Netherlands the lev el of parasitization is often too low, especially after warm winters. The b iological control potential of a strain of A. mali from Nova Scotia (Canada ) was compared with a Dutch strain by simulating population growth of both WAA and the Dutch and Canadian strain of the parasitoid for three different years The results indicate that the Canadian strain would perform in gener al better than the Dutch strain under Dutch weather conditions.