DISTRIBUTION, PREFERENCE AND PERFORMANCE OF PHORACANTHA RECURVA AND PHORACANTHA SEMIPUNCTATA (COLEOPTERA CERAMBYCIDAE) ON VARIOUS EUCALYPTUS SPECIES IN TUNISIA (1)

Abstract

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.