Cactus Moth Poses New Invasive Species Threat to Texas Biodiversity

Tom Harvey, 512-389-4453,

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AUSTIN — The cactus moth (Cactoblastis cactorum), a non-native insect species from South America, is spreading westward along the Gulf Coast towards Texas. The invasive pest could do significant economic and ecological damage if it reaches Texas, and authorities trying to monitor the path of the moth are asking the public to help prevent it from spreading.

The moth’s preferred food is prickly pear (Opuntia species) and the insect is capable of rapidly destroying entire stands of the plant. North America is home to more than 100 prickly pear species that are highly valued for agricultural and ecological benefits.

The U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) has proposed mending its foreign quarantine regulations to prohibit people from importing prickly pear cactus nursery stock or cactus edible fruits and pads from countries infested with the moth. Meanwhile, people should take care when importing prickly pear into Texas.

People can see photos and learn more about the cactus moth and the types of cacti it infests on the website of the Cactus Moth Detection and Monitoring Network, a coalition formed to monitor the spread of the moth. The network is welcoming volunteers willing to help monitor prickly pear populations in Texas. Learn how to volunteer on the network website, or contact Victor Maddox, PhD, at (662) 325-2313 for survey protocols and volunteering details.

Prickly pear is used for a variety of products including food for humans and livestock, cosmetics, dyes, and medicines. Research studies in 2001 and 2004 showed the agricultural value of prickly pear in the United States (principally in Arizona and California) at more than $31 million per year. Likewise, a 2002 study put the plant’s value in Mexico at more than $50 million per year.

Ecologically, prickly pear is an important component of natural ecosystems. Its structure provides shade and resting habitat for many birds and reptiles, including such species as the cactus wren, curve-billed thrasher, mourning dove, and roadrunner. Prickly pear fruit are eaten by birds, deer, jackrabbits, javelina, raccoon, rodents, and tortoises. The plant’s flowers comprise vital sources of pollen and nectar for hundreds of insect species.

Native to Argentina, southern Brazil, Paraguay, and Uruguay, the cactus moth was first used in the 1920s as an agent of prickly pear control in Australia where the plant had been introduced years earlier. Prickly pear was not native to Australia and, like other exotic species transplanted outside of their original range, became invasive and quickly spread across the landscape with devastating impacts on agriculture. The cactus moth proved extremely effective in reducing Australia’s prickly pear infestation. Given its success in that country, cactus moths were released to sites in the Caribbean in the 1950s to control prickly pear. It did not stay in the Caribbean for long, however.

In 2009, cactus moth populations were found in Jefferson Parish, Louisiana just south of New Orleans. Cactus moth populations are now just 240 miles from Texas. The likelihood that this insect will make its way to points along Texas’s coast is high. Adult moths, while small, are capable of dispersing distances of up to 16 miles and may arrive on their own. Ornamental prickly pear brought into the state from infested areas represents another potential avenue of entry. If the cactus moth does successfully invade Texas it would have access to stands of prickly pear across the southwestern United States and Mexico.

The adult cactus moth is non-descript and difficult to identify. The best detection strategy is to look for the moth’s caterpillars and evidence of feeding damage. Mature cactus moth caterpillars are distinct with a characteristic orange to red coloration interrupted by dark banding or spots. Feeding damage is also distinctive. Cactus moth larvae live and feed communally inside the pads of prickly pear. Damaged pads will exhibit oozing of sap and insect droppings. Eventually the pad will become transparent and hollow, collapsing shortly thereafter.

Knowing where the cactus moth occurs is a vital first step in monitoring population expansion and controlling its spread. Several federal and state agencies, universities, and other interested groups have formed the Cactus Moth Detection and Monitoring Network to monitor the spread of the moth. In Texas, Texas A&M University faculty members are currently leading trapping efforts to detect the species’ arrival in the state. Texas Parks and Wildlife Department employees have also been trained in cactus moth detection.

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