BIOLOGICAL-CONTROL OF PRICKLY PEAR, OPUNTIA-FICUS-INDICA (CACTACEAE), IN SOUTH-AFRICA

The outstanding success of a cochineal insect, Dactylopius opuntiae (Cockerell), and, to a far lesser extent, a phycitid moth. Cactoblastis cactorum (Bergroth), in biocontrol of the prickly pear, Opuntia ficus-indica (L.) Miller, in South Africa was fully reviewed in 1978. The present account updates this information. Today, the weed infests less than 100 000 ha (of the 900 000 ha originally colonized) in the cooler, higher rainfall areas where D. opuntiae, is relatively ineffective. Cactoblastis cactorium is able to kill only the small prickly pear plants and suffers losses because of ant predation, climatic extremes and, partly, to host plant incompatibility. Integrated chemical and biological control methods are described which allow O. ficus-indica to be managed as necessary and also to be exploited as a drought fodder for stock, as a fruit and vegetable source for humans, and as a host plant for the commercial production of dye stuff from the cochineal. Dactylopius coccus O. Costa. As a result of successful biological control over the past 50 years, the public has forgotten the former severity of the prickly pear weed problem in South Africa. The residual O. ficus-indica populations are now highly valued and the biological control agents themselves are regarded as pesis. The consequences of these changed perceptions are discussed.