[Show abstract][Hide abstract] ABSTRACT: Environmental stresses, particularly water deficit, predispose eucalypt trees to attack by the eucalyptus longhorned borer,
Phoracantha semipunctata F. (Coleoptera: Cerambycidae). Our experiments with potted eucalypts revealed that reduced tree water potential was associated
with lower resistance to colonization by neonate P. semipunctata, but the linear relationship between water potential and colonization success was reversed at higher larval densities. There
was no indication that the bark exudate “kino” served to defend trees from borer attack. Larvae were not able to colonize
the cambium of eucalypt logs with high bark moisture, and survival was low under high moisture conditions in artificial hosts
composed of pure cellulose. In trees and cut logs with moist bark, larvae failed to reach the cambium, feeding instead in
poorer-quality tissues just beneath the bark surface. Our findings suggest that variation in resistance of eucalypts to attack
by the borer is associated with moisture content of the bark.