Geographical range and impact of five biocontrol agents established on Lantana camara in South Africa

A survey was conducted to determine the present status of five biocontrol agents established on Lantana camara L. (Verbenaceae) in South Africa. Three of the five agents, Calycomyza lantanae (Frick), Ophiomyia lantanae Froggatt and Teleonemia scrupulosa Stal are established throughout the range of L. camara. The two hispine beetles, Octotoma scabripennis Guerin- Meneville and Uroplata girardi Pic are restricted to the warm, subtropical regions in the eastern range of the weed, and are unable to cope with the plants becoming seasonally leafless in dry and temperate areas. The two beetles and T. scrupulosa are rated as the most damaging agents on L. camara. The impact of O. lantanae is uncertain, and due to low populations, the impact of C. lantanae is negligible. Insect populations typically accumulate to maximise their impact on plants by midsummer, giving plants the opportunity to compensate for the cumulative agent damage accrued at the end of the previous growing season. A number of parasitoids were reared from U. girardi, O. lantanae and C. lantanae, but only those adapted to C. lantanae are expected to significantly reduce its field density. The agents feed and develop on a wide range of lantana varieties, and where two or more varieties co-exist, insects occurred in equal abundance on the different varieties. The importance of varietal preferences appears to have been over-estimated, but needs consideration when new candidates are evaluated. The impact of these biocontrol agents is insufficient to reduce L. camara to a manageable situation, and additional candidates are necessary to control this weed in South Africa.