Prickly pears no match for moths
By JAMES PINKERTON
Copyright 2007 Houston Chronicle
RESOURCES
UNWANTED PEST
• Common name: Cactus moth
• Scientific name: Cactoblastis cactorum
• Origin: Native to Argentina, Paraguay, Uruguay and Brazil
• Adult moth: Brownish-gray with two wavy bands on wingtips
• Larvae: Reddish-orange body with bands of black dots
• Food: Larvae feed on pads of prickly pear cactus
• Proximity to Texas: Moving west from Alabama, confirmed in Mexico
MISSION — First there were fire ants. Then came killer bees.
Now, the voracious South American cactus moth is migrating steadily toward Texas. Scientists and naturalists worry the nondescript invader could decimate the trademark stands of prickly pear cactus that figure in both the landscape and lore of much of Texas.
"If it gets established in Texas, the worst-case scenario is, it would wipe out the prickly pear cactus in South Texas," said Lisa Williams, the Nature Conservancy's director of the Tamaulipan Thornscrub project. "I don't know what other species we have that could replace its ecological function in the brush."
Since arriving in Florida in 1989, the cactus moth has winged along the Gulf Coast at a rate of at least 50 miles a year, scientists say. The invasive moth has reached Dauphin Island off the Alabama coast and is expected to reach East Texas sometime in 2008.
In August, the cactus moth also was discovered in Mexico on Isla Mujeres, an island opposite Cancun on the Yucatan Peninsula.
"It's coming from two directions, and Texas is caught in the middle," Williams said. "It is definitely a very real threat."
Many depend on plant
If left unchecked, Williams added, the moth could devastate the 19 species of prickly pear cactus found across Texas and create a damaging ripple effect on wildlife that depend on the plant for food, shelter or protection.
In addition to preventing soil erosion, the prickly pear — the state plant of Texas — is an important food for a number of birds and mammals, including white-tailed deer, coyotes, rabbits, foxes and javelina. Other creatures, including the bobwhite quail and the cactus wren, rely on the prickly pear for shelter or protection from predators.
The moth's impact also be great south of the border could, where 53 varieties of prickly pear grow and are important cash crops.
In Mexico, the prickly pear pads and fruit are harvested for dye and food. Prickly pear cactus accounts for more than 2 percent of Mexico's agricultural production, according to Barron Rector, a range specialist with the Texas Cooperative Extension in College Station.
How to spot them
Already, Texas plant experts are examining shipments of ornamental prickly pear in nurseries for signs of the cactus moth and following up on a few suspicious sightings by nervous landowners, Rector said.
"My greatest concern is, people don't know what a cactus moth looks like and don't understand what to look for," Rector said. "It could already be here ... and nobody has noticed it."
There is one good way to spot the intruder.
Although the brownish-gray cactus moth is similar to many native to Texas, Rector said the female produces bright orange larvae adorned with black spots. The colorful larvae burrow inside the cactus pads and eat the plant from the inside out.
The cactus moth has been used in the past as a biological agent to control prickly pear cactuses introduced in Australia, South Africa, India and Hawaii. In a little more than a decade back in the 1920s, the moth cleared 80 million acres of prickly pear cactuses in Australia, Rector said.
"The cactus moth is good at what it does — destroying cacti," the range expert said. "But If we do the right things, we'll have a better control over this problem. We think education is the key."
Other threatening species
The cactus moth is the latest of a host of invasive species to threaten Texas.
So far, biologists have confirmed the presence of dozens of non-native species, including 67 land plants, 12 aquatic plants, 10 mammals, four birds, seven fish and 11 insects, along with 11 crustaceans and mollusks, according to researchers at Texas A&M University.
The red fire ant, another South American native, has spread to a number of Southern states, including Texas, since arriving in Alabama in the 1920s. The aggressive ant kills newborn livestock, and millions of dollars are spent each year to control it.
Africanized "killer" bees, have quickly spread through the southern United States, reaching as far west as Nevada and California since crossing the Rio Grande in 1990. The wild bee has cost beekeepers millions of dollar in lost honey production, and its sting has injured and killed people.
Attacking reproduction
The most promising strategy to stop the advance of the cactus moth, experts agree, is a sterile breeding program, and trials by U.S. Department of Agriculture researchers are under way in Alabama. The federal project raises sterile males for release in the wild.
"If nothing is done, the cactus moth will reach Texas and prickly pear cactus will be devastated," Williams said. ''The USDA needs to receive full funding to ramp up the sterile-male release program in order to eradicate the cactus moth."
james.pinkerton@chron.com
