干旱区生态环境知识资源中心

The two eucalyptus borers Phoracantha semipunctata and P. recurva were accidently introduced in Tunisia in 1962 and 1999, respectively. Their relative distribution is still unknown and very little is known about their preferences and performances in various host species under different Tunisian climates. We combined field data and laboratory follow-up, in order to define their present distribution, their relative abundance and to test the effects of sites and Eucalyptus species on attack density, reproductive and developmental performances and productivity of insects. The study was carried out in Eucalyptus plantations of ten localities ranging from humid to arid. Choice preference and colonization of various selected Eucalyptus species by the two borers were studied with standing trap trees and trap logs. Tree species differed among localities, but all localities contained at least one of the two species E. gomphocephala and E. camaldulensis, both being well appreciated by the two Phoracantha species. It appeared that both beetle species were present in all localities but P recurva was dominant over P semipunctata everywhere. Insect characteristics depended on attack localization on tree stem; attack densities were higher on the lowest than on the upper parts. It is perfectly coherent that the density of emerging beetles correlated positively with attack density, number of young larval galleries, larval survival and adult success in the trap tree experiment. High larval survival and adult success resulted in high offspring productivity. Insect parameters, especially the intensity of infestation, depended on locality but without relation with the climatic areas.