Intraspecific variation in beech scale populations and in susceptibility of their host Fagus sylvatica

Abstract

ABSTRACT. Within a seed orchard in southern England, beech trees (Fagus sylvatica L.) belonging to three clones were artificially infested by introducing beech scale larvae (Cryptococcus fagisuga Lind. Homoptera: Coccidae) into small cages attached to the bark. Some larvae developed to fecund adults on trees of two susceptible clones but all failed to develop on a third, resistant clone. Within susceptible clones, survival of larvae on individual trees was positively related to their degree of natural infestation. Larvae deriving from several separate trees differed significantly in their ability to survive when inoculated onto trees of susceptible clones. Five forest trees which acted as both donors of larvae and as hosts for artificial inoculation were each inoculated with larvae from all five trees. There was significant variation in survival of inoculated larvae both between the host trees and between sources of larvae on each host. Survival of larvae reinoculated onto their original host was significantly higher than that of larvae originating from other trees. Fecundity of adults on the forest trees was positively correlated with the probability of inoculated larvae surviving to the adult stage.