Potential Agents for the Biological Control ofTecoma stans(L.) Juss ex Kunth var.stans(Bignoniaceae) in South Africa

Abstract

Tecoma stans (L.) Juss ex Kunth var. stans (Bignoniaceae), known as yellow bells, was introduced into South Africa as an ornamental plant and now invades roadsides, urban open spaces, watercourses and rocky sites in the subtropical and tropical areas of six South African provinces, and neighbouring countries. Although deemed to be an ‘emerging weed’, Tecoma stans has considerable potential to extend its range because it is still common in South African gardens and its seeds are easily dispersed by wind. Mechanical and chemical control methods are not economically feasible as the plant tends to re-grow, thus requiring expensive follow-up treatments. Biological control research on T. stans has been ongoing since 2003, when pathogens were the focus as agents, with insects included since 2005. Five candidate agents have so far been tested in South Africa, with one, Clydonopteron sacculana Bosc (Lepidoptera: Pyralidae), deemed unsuitable for release, one, Prospodium transformans (Ellis & Everh.) Cummins (Pucciniales: Uropyxidaceae), released initially in November 2010, and another, Pseudonapomyza sp. (Diptera: Agromyzidae), currently awaiting approval for release by the regulatory authorities. One candidate agent, Mada polluta (Mulsant) (Coleoptera: Coccinellidae), is still under investigation in quarantine. The last potential agent, a root-feeding flea beetle, Dibolia sp. (Coleoptera: Chrysomelidae), was brought into South Africa but the culture did not establish in quarantine.