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Australia's Cactus Crisis: A Moth's Triumph
10 Oct
Summary
- Prickly pear once covered 60 million acres in Australia.
- Cochineal insects were initially brought for red dye production.
- A moth species, Cactoblastis cactorum, was later introduced to control the cactus.
In the late 18th century, prickly pear cacti were intentionally introduced to Australia from Brazil, initially for the cochineal insect dye industry. However, the plants proved far more resilient than the insects. By the mid-1800s, settlers introduced new varieties for hedges and fodder, leading to an unchecked spread west of the Great Dividing Range.
This invasive cactus soon overwhelmed farmland and native vegetation, covering an estimated 60 million acres in New South Wales and Queensland by the early 1920s. Despite legislative efforts and substantial rewards offered for control methods, the prickly pear continued its advance unchecked.
In 1926, a biological control program was initiated with the introduction of the Cactoblastis cactorum moth from Argentina. The moth's larvae proved highly effective, feeding on and destroying the cactus. By 1933, significant portions of infested land in Queensland had been cleared, although the prickly pear remains a persistent issue.
The Cactoblastis cactorum moth, a solution in Australia, has since caused problems elsewhere. Introduced to the Caribbean in 1957, it attacked native Opuntia species and later spread to Mexico, damaging commercial crops. Concerns also exist about its potential impact on important Opuntia species in the southern United States, illustrating how biological controls can create new ecological challenges.
