Positive effect of drought on longicorn borer larval survival and growth on eucalyptus trunks

Abstract

Phoracantha semipunctata (F.) larvae attack and kill trees in Eucalyptus globulus (Labill.) plantations in Mediterranean countries. To test the hypothesis that these attacks are more likely in arid environments, we examined the effects of water deficits in the host trees of E. globulus on the mortality and growth of P. semipunctata larvae. Trees subjected to water stress during two subsequent years were compared with rainfed and irrigated trees. Larvae of P. semipunctata were artificially introduced in the bark of trees of either treatment. Larvae mortality was lower and weight gain was higher in water stressed trees than on rainfed trees. There was no larvae survival in irrigated trees. These results were related to changes in moisture content and concentration of soluble sugars in the bark of the trees. The results of this study suggest that water stress had a major role on the survival and growth of the larvae.