Africa as a source for weed biological control agents

Authors: PATERSON, IAIN - Rhodes University; Wheeler, Gregory; PAYNTER, QUENTIN - Landcare Research; Moran, Patrick; PLOWES, ROB - University Of Texas At Austin

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/14/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Africa is a major source of invasive weeds to other parts of the world including the USA. There are 1863 plants indigenous to African that are naturalized outside of the continent and, of the 200 most widely distributed invasive plants globally, 40 are of African origin. Despite being a source of invasive plants, there are few cases of biocontrol agents from Africa being released elsewhere. Only 24 species of African origin have ever been released as biocontrol agents, with only eight released in North America. The majority of the agents were sourced from South Africa (58%), with others from Kenya, Morocco, Ghana, Tunisia and Egypt. The most recent releases of agents sourced in Africa are a plant feeding mite and the flea-beetle, which were sourced in Ghana and released in the Cook Islands for the control of African tulip tree. Further surveys for additional agents for this weed are currently underway in Cameroon. Weeds that are problematic in North America include Cogongrass where surveys are being conducted in East Africa; Crystalline ice-plant for which a promising candidate, the stem-mining weevil from South Africa, has been prioritized; and Guineagrass where two stem-galling midges and an undescribed seed-feeding midge are currently undergoing host specificity testing in South Africa. Africa is a largely untapped resource of biocontrol agents for invasive alien plants both globally and in North America, with many opportunities for developing new biocontrol programmes.

Technical Abstract: Africa is a prolific donor of invasive alien plants to other parts of the world. There are 1863 plants indigenous to African that are naturalized outside of the continent and, of the 200 most widely distributed invasive plants globally, 40 are of African origin. Despite being a donor of invasive plants, there are few cases of biocontrol agents from Africa being released elsewhere. Only 24 species of African origin have ever been released as biocontrol agents, with only eight released in North America. The majority of the agents were sourced from South Africa (58%), with others from Kenya, Morocco, Ghana, Tunisia and Egypt. The most recent releases of agents sourced in Africa are the Eriophyid mite, Colomerus spathodeae, and the flea-beetle, Paradibolia coerulia, which were sourced in Ghana and released in the Cook Islands for the control of African tulip tree (Spathodea campanulata). Further surveys for additional agents for this weed are currently underway in Cameroon. Weeds that are problematic in North America include Cogongrass (Imperata cylindrica) where surveys are being conducted in East Africa; Crystalline ice-plant (Cryophytum crystallinum) for which a promising candidate, the stem-mining weevil Lixus carinerostris from South Africa, has been prioritized; and Guineagrass (Megathrysus maximus) where two stem-galling midges (Arabukodiplosis basalis & A. vesicaria) and an undescribed seed-feeding midge are currently undergoing host specificity testing in South Africa. Africa is a largely untapped resource of biocontrol agents for invasive alien plants both globally and in North America, with many opportunities for developing new biocontrol programmes.