POTENTIAL AND RISKS OF BIOLOGICAL CONTROL OF CACTOBLASTIS CACTORUM (LEPIDOPTERA: PYRALIDAE) IN NORTH AMERICA

Abstract

Cactoblastis cactorum Berg, an invasive moth and famous biological control of weeds agent, threatens numerous native and economic prickly pear cacti (Opuntia) in the United States and Mexico. Biological control of the moth, using a variety of approaches, is considered including: introduction of parasitoids and pathogens from the moth's native home in South America, introduction of parasitoids from related North American cactus moths (Pyralidae: Phycitnae), inundative releases of parasitoids known to attack the moth in Florida, and inundative releases of mass reared generalists parasitoids. The primary risk of employing biological control is the reduction of the many North American cactus moths, some of which probably regulate native Opuntia that can be weedy. The various biocontrol approaches are ranked according to their relative risk to the native cactus moths. The introduction of South American parasitoids or pathogens specific to the genus Cactoblastis (if they exist) may be the least risky approach. The introduction of South American parasitoids that can attack many cactus moths is the most risky approach because it could result in persistent "control" of these non-target native insects. Biological control probably can reduce the abundance of C. cactorum populations but is unlikely to prevent the spread of the moth. The relative benefits and risks of biological control need to be carefully assessed prior to any operational biological control programs. It will be difficult to reach agreement on acceptable levels of risk, if the likely benefits can't be predicted. Other management options need to be considered.