“The introduction of Opuntia cacti to Australia in 1832 as hedging plants caused an ecological disaster. By 1925, several species were spreading through Australia like wildfire. A variety of control measures proved ineffective until 1925, when the Argentinian moth Cactoblastis cactorum was introduced, the larvae of which feed on the cacti. By 1933, 90% of the cacti had been eradicated. A similar situation occurred in South Africa with O. ficus-indica covering a huge territory before suitable biological control agents (a weevil and a beetle as well as the moth used in Australia) were found in the 1930s. (Ironically, cactus pear is now considered a valuable crop in South Africa, and farmers growing it there have great difficulties controlling the biological control agents.)”