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Invasive cactus moth threatens prickly pear, agriculture and wildlife

Texans are asked to keep an eye out for caterpillars

Prickly pear cactus has been reviled and rhapsodized, but there is no doubt it is an essential element in the landscape, the culture and even the economy of Texas, Mexico and throughout the Southwest.

Now, the prickly pear is under attack from an invasive, non-native cactus moth whose orange-and-black caterpillars devour the cactus if left unchecked.

Since its arrival in Florida in 1989, the cactus moth (its scientific name is Cactoblastis cactorum) has eaten its way up the Atlantic coast to South Carolina and across the Gulf coast to Alabama. Scientists fear it could devastate the prickly pear cactus of Mexico and the Southwest, and at the rate it’s traveling, it may reach Texas in 2008. Recently, the cactus moth was discovered on Isla Mujeres, an island only 8 miles from Cancun on Mexico’s Yucatan Peninsula.

“The discovery of the cactus moth on Isla Mujeres has raised concerns it could quickly reach the Mexican mainland, where there are 53 species of prickly pear,” said Jim Bergan, Ph.D., The Nature Conservancy’s Texas director of science. “From Mexico, the moth could move easily to Texas and the Southwest, with potential devastating effects on wildlife habitat and rural economies.”

Prickly pear is used as emergency food for cattle during drought, and it is a major agricultural crop in Mexico, where its fruit (called “tuna”) and pads are harvested as food for people. It is also a mainstay of the nursery industry as an ornamental and landscaping plant.

“We realize that prickly pear can be a problem for some cattle operations,” Bergan said. “However, we also know that the cactus helps maintain soil stability by reducing erosion, provides shelter for the establishment of other plants and it is essential to many species of birds and mammals for food, shelter and protection from predators. There are data available that have documented its importance to white-tailed deer, javelina, bear, bobwhite quail, cactus wren and curve-billed thrasher.”

It is the cactus moth’s voracious appetite for prickly pear cactus that set it on its path of destruction. Originally from Argentina, the moth was introduced to Australia in the 1920s as a biological agent to help control the cactus, which had been introduced and became invasive. For the same reason, the moth also was introduced to India, South Africa and Hawaii. It is speculated it was unintentionally introduced to Florida via imported ornamental cacti.

A more advanced biological technique now holds the most promise for combating the spread of the cactus moth.

“The Nature Conservancy has been promoting the implementation of the release of sterile male cactus moths developed by the U.S. Department of Agriculture,” said Bergan. “This technique involves releasing large numbers of sterile male moths. The sterile males mate with females, and no larvae, or caterpillars, are produced. If enough sterile males are released, the number of successful matings could be greatly decreased.”

The female cactus moth lays her eggs on the pad of the prickly pear cactus. The eggs are layered on top of each other to form what biologists call an “egg stick,” which resembles a cactus spine and contains 60 to 100 eggs. After three or four weeks, the caterpillars hatch and burrow down into the pad of the cactus.

“The cactus moth itself is brown and looks like many common species of moth, but the caterpillars are distinctive – bright orange-red with black bands that are actually groupings of spots,” Bergan said.

Landowners in Texas are encouraged to keep an eye out for prickly pear that look brown, hollow, transparent and/or riddled with holes. Suspicious pads can be broken open to reveal the brightly colored caterpillars.

“We’re asking anyone who believes they are seeing cactus moth caterpillars to report it,” said Bergan. “The sooner we become aware that the species has appeared in Texas, the better we can combat the invasion.” Those who believe they have seen the caterpillars are asked to contact Barron Rector, Ph.D., with Texas Cooperative Extension, at brector@ag.tamu.edu or (979) 845-2755.

Photo download:

cactus moth
Photo Credit: © Used by permission of the Joint FAO/IAEA Programme; Nuclear Techniques in Food and Agriculture (above photo credit must be included if image is used) 
Photo Caption: Cactus moth threatens to devastate Texas, Mexico habitat

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The Nature Conservancy is an international, nonprofit organization that preserves plants, animals and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive. To date, the Conservancy and its nearly 1 million members have been responsible for the protection of more than 15 million acres in the United States and have helped protect more than 102 million acres in Latin America, the Caribbean, Asia and the Pacific. In the Lone Star State, The Nature Conservancy of Texas owns 35 nature preserves and conservation projects and assists private landowners to conserve their land through more than 70 voluntary land-preservation agreements. The Nature Conservancy of Texas protects 250,000 acres of wild lands and, with partners, has conserved close to a million acres for wildlife habitat across the state. Visit The Nature Conservancy of Texas on the Web at nature.org/texas.