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Tiny Moth: A Giant Victory Over Invasive Cactus
16 Jul
Summary
- Prickly pear covered over 24 million hectares by the early 1900s.
- A South American moth became a highly successful biological control agent.
- The moth's larvae destroyed 80% of the cactus infestation within seven years.
In the early 1900s, Australia faced a severe environmental crisis as prickly pear rapidly spread across millions of hectares, primarily in Queensland and New South Wales. Initially introduced for a cochineal dye industry in 1788, the non-native Opuntia species flourished, outcompeting native plants and covering vast tracts of land. Governments enacted measures like the Prickly-Pear Destruction Act in 1886 and offered a £5,000 prize for a solution, but methods like salt, arsenic, and mirrors proved ineffective.
Frustrated by costly and unsuccessful mechanical and chemical controls, scientists turned to biological control. After extensive research in the Americas, the cactus moth, Cactoblastis cactorum, was introduced to Queensland in 1926. The moth's larvae proved devastating to the prickly pear, burrowing into the pads and killing the plants from within.
This biological control project was remarkably successful. Within seven years, the Cactoblastis moth had eradicated approximately 80 percent of Australia's prickly pear infestation. This effort returned millions of hectares of valuable grazing and farming land to productive use, earning the moth a place of honor, including a memorial hall in Queensland. The success story of the prickly pear control continues to be a landmark example in invasive species management worldwide.
