Eucalyptus Weevil – Peter Woodall

Eucalyptus Weevil Gonipterus scutellatus

During the recent QNC outing to Anstead on 12 July, we came across this tiny little beetle. When we got the images home we were able to identify it as the Eucalyptus Weevil Gonipterus scutellatus, which is only 13mm long. Native to Australia, it feeds on the young shoots of eucalypts. It has been introduced to New Zealand; China; many countries in Africa;

Brazil Chile, and the United States; and to France, Italy, Portugal and Spain in Europe. Females lay 200 eggs, in batches of 10, on the underside of eucalypt leaves. They thatch after about a week and the larvae feed on the leaves and young shoots of eucalypts. After moulting three times the larvae pupate in the ground. The complete life cycle takes 7-11 weeks.

It is of little economic significance in Australia where it has natural enemies but in other countries where eucalypts have been introduced, it has become a pest. Adult gum tree weevils feed mostly on leaves and the soft bark of twigs while the larvae feed mostly on leaves. Heavy infestations cause die back of shoots which may result in the development of epicormic shoots. Repeated defoliations can cause the death of branches or even whole trees.

A native wasp Anaphes nitens which is an egg parasite, has been introduced to other countries as a biological control agent for the gum tree weevil. This has been successful in Mauritius where in two years, the incidence of the gum tree weevil has been much reduced. More recently, successful control has also been obtained in Italy, France and in Spain.