Recent Advances in the Biological Control of Tecoma stans L. (Bignoniaceae) in South Africa

Abstract

Tecoma stans (L.) Juss ex Kunth var. stans (Bignoniaceae) is an invasive shrub or small tree from Central America that continues to extend its range in all nine provinces of South Africa and in neighbouring countries. The weed has been a target for biological control (biocontrol) in South Africa since 2003. The gall-forming rust fungus Prospodium transformans (Ellis & Everh.) Cummins (Pucciniales: Uropyxidaceae) was released in 2010, but failed to establish. Two leaf-feeding agents, Mada polluta (Mulsant) (Coleoptera: Coccinellidae) and Pseudonapomyza sp. Hendel (Diptera: Agromyzidae), were subsequently released in South Africa in 2013 and 2014, respectively. Mada polluta has become established at seven sites in the low elevation coastal regions of the Eastern Cape and KwaZulu-Natal provinces, but not in high elevation inland areas. The leaf-mining Pseudonapomyza sp. has established at seven sites in four provinces, namely the Eastern Cape, KwaZulu-Natal, Limpopo and Mpumalanga, but at low population densities. The deliberate destruction of release sites by landowners and inadvertent veld fires have confounded the establishment and proliferation of both agents, as well as progress on their post-release evaluation. A root-feeding flea beetle Heikertingerella sp. Csiki (Chrysomelidae: Galerucinae), initially collected in Mexico in 2007, was determined to be host specific and potentially effective as a new biocontrol agent of T. stans. An application for the release of Heikertingerella sp. in South Africa will shortly be submitted to the regulatory authorities. Additional mass-rearing and releases of the two established agents will be undertaken to improve their establishment and impact.