Biology, oviposition preference and impact in quarantine of the petiole-galling weevil, Coelocephalapion camarae Kissinger, a promising candidate agent for biological control of Lantana camara

The petiole-galling weevil, Coelocephalapion camarae Kissinger (Coleoptera: Brentidae), native to Mexico, was introduced into quarantine in South Africa to evaluate its potential to supplement the biological control programme against the invasive varieties of Lantana camara L. (Verbenaceae). The weevil occurs over a wide, native, geographic range, indicating its physiological potential to establish and persist throughout the range of climatic conditions under which the target weed grows in South Africa. The adults are highly selective in their choice of oviposition site, and only leaf-petioles with a width larger than 1.5 mm are accepted. Emerging larvae burrow into the vascular tissue and induce gall formation. Galling disrupts the transport of water and nutrients to and from the leaf, causing it to desiccate. During glasshouse studies the effect of galling on plant growth was tested on two different lantana varieties. The apionine both reduced lantana biomass accumulation (from 2 to 43% dry mass), and altered subsequent resource allocation away from the roots in both lantana varieties. Root growth increment loss over the duration of the trials on medium-density beetle-colonized plants (10 adult pairs) was between 109 and 144%, and increased from 109 to 117% in high-density beetle-colonized plants (20 adult pairs). These studies suggest that C. camarae could make a valuable contribution to the biocontrol programme against L. camara, and that studies on its host specificity are warranted.