Field and laboratory biology of the stem-feeding beetle Thamnurgus euphorbiae (Kuster) (Col., Scolytidae) in Italy, a potential biological control candidate of leafy spurge in the USA and Canada

Thamnurgus euphorbiae overwinters as adults in dry stems of Euphorbia characias until the end of March before exiting through circular holes cut with their mandibles. Females and males appeared in the field at the same time, and the first pairs were observed on 28 March on new stems of E. characias having the open-flower at the beginning of its development. Throughout the rest of April it was possible to find and collect the fairly abundant adults. Mating occurs on new stems of the host plant and females walk up towards the top of the stem and start to mine the centre of it in order to penetrate. Oviposition occurs in new stems and eggs are laid singly along the interior of the stem; females laid 35-85 eggs. Upon hatching, larvae started feeding on vascular bundles and the inner cortex. There are three larval instars, and pupation occurred in the stem of the host plant; this insect is univoltine. Thamnurgus euphorbiae has been accepted by the Technical Advisory Group for Biological Control Agents of Weeds for release as a biological control agent of leafy spurge in the US. Prior to this study the biology of T. euphorbiae was unknown.