Prickly pear had taken over 60 million acres (24.3 million hectares) of land in New South Wales and Queensland before moths were released in 1926 to fight it, according to the National Museum of Australia . The cactus was first introduced into Australia in 1788, and it was done so on purpose. Ever picked up a cute plant on a whim, only to see it take over your balcony? Now imagine that happening on a massive scale. It may sound unlikely, but it happened in Australia. That land became unusable for farming.
They found that insects and plant diseases attacked the cactus there. The larvae feed on the soft tissue within the cactus pads and can kill an entire plant in weeks. In 1913, Queensland organized a team of biologists who traveled to North and South America, where prickly pear is native. In 1920, three governments set up the Commonwealth Prickly-Pear Board to study these natural controls. The first two attempts to breed Cactoblastis cactorum in the early 1920s failed, so 3,000 eggs were brought in from Argentina , where the moth is native to a small area. The first releases of moths were made in 1926. At the height of the program, Chinchilla in Queensland was sending out up to 14 million eggs a day. By 1933, about 80 percent of the infested land in Queensland had been cleared, according to the Queensland State Archives. The museum puts the figure at 50 to 60 percent for New South Wales.
Prickly pear is not gone forever. It is still a problem in New South Wales and Queensland, but not to the crisis proportions of the 1920s, as new varieties that do not act as hosts for the moths have become established. There are also serious concerns the moth could damage important Opuntia species throughout the southern United States. The story shows how moving a species to a new place can solve one problem and create another.
The same moth was introduced to the Caribbean in 1957, where native Opuntia species had never encountered it before.
The museum says the moth attacked local species and moved to Mexico, where it has begun destroying the country’s commercial Opuntia crop.
