Influence of phenolglucosides and trichome density on the distribution of insects herbivores on willows

The effects of both trichome density and phenolglucoside content of leaves of 76 willow hybrids (<i>Salix alba</i> x <i>fragilis</i>) were measured to estimate their influence on the distribution of <i>Phratora vitellinae</i> (L.), <i>Plagiodera versicolora</i> Baly (Coleoptera: Chrysomelidae) and <i>Pontania proxima</i> (Lepeletier 1823) (Hymenoptera: Tenthredinidae) in a nursery at Gramont, Belgium. <br> The willows showed differences in their phenolglucoside content and pilosity of leaves and are classified on these basis into four groups by a clustering method. Correlations and multiple regressions showed that these chemical and physical characteristics are good predictors of the abundance of insects. First, the abundance of larvae of <i>Ph. vitellinae</i>, adults of <i>Pl. versicolora</i> and galls of <i>P. proxima</i> is correlated positively with a high phenolglucoside content and a low pilosity of the leaves. Secondly, the distribution of adults of <i>Ph. vitellinae</i> and of larvae of <i>Pl. versicolora</i> is influenced by neither the chemical nor the physical leaves characteristics studied.