When a cactus moth lays its eggs on an Opuntia cactus, it creates one of nature’s most effective camouflages. The eggs emerge as what is called an “egg stick”, because they look like the cactus spine. The problem is that when the larvae emerge from the dozens of eggs that make up the egg stick, they survive by eating – and destroying – the cactus leaf pads. The cactus moth is an invasive species native to South America, including northern Argentina, Uruguay, Paraguay and southern Brazil, but after its initial introduction to the Caribbean for research purposes, it expanded its range to the Caribbean islands and eventually to the Florida Keys off the US Gulf Coast. It also infested two islands off the Yucatan Peninsula, from which it threatened Mexico’s enormous commercial cultivations of Opuntia as well as the arid ecosystems of the area that depend on Opuntia cactus for soil and wildlife conservation. The threat was enough to bring Mexico’s Ministry of Agriculture, the US Department of Agriculture (USDA), the Joint FAO/IAEA Division and IAEA’s Technical Cooperation Department together to implement an eradication programme to curtail the Yucatan infestation. However, despite its success, the moth threat remains.
The Opuntia cactus can be fried as a vegetable, eaten raw as a fruit, used as forage for livestock, added as an ingredient in botanical medicines, planted in rows as border hedges, or left to propagate in arid areas where it contributes to soil conservation and serves as a water or food source for wildlife. In Mexico, where this cactus is considered a staple food, some 300 000 tonnes are produced for consumption each year by 30 000 producers and another 28 000 are employed in processing and packing facilities.