March 15, 2010

Pest Control: Invasion of the Cactus Moth

Print More

Across the southern United States, a predator hides among the cacti. The cactus moth, scientific name Cactoblastis cactorum, is an invasive species that destroys prickly pear cacti from Florida to Texas.

Prof. Mark Sarvary, neurobiology and behavior, presented his research on the ravenous insect yesterday in Corson/Mudd Hall.

Originating from Argentina, the moth journeyed around the world through intentional introductions to control prickly pear populations in Australia, South Africa, Hawaii and the Caribbean. The invasive species arrived in the states via the Florida Keys in 1986. With no natural predators in the US, the cactus moth spread west to Texas.

“It completely destroys the plant. That’s why it’s so dangerous for all these cactus specimens,” Sarvary explained. “If Cactoblastis fed on a plant, the plant is not going to come back.”

The cactus moth’s destructive appetite both scares citizens of the US and Mexico. In the U.S., the moth destroys endangered prickly pear species and causes soil erosion problems. If the moth spreads to Mexico, it could cause serious damage to prickly pear crops — known as “nopales” — that make up 2.5% of Mexico’s GDP, according to Sarvary.

No successful control methods exist … yet. One promising control method, called “Sterile Insect Technique (SIT),” creates sterile males that compete with fertile ones during mating to female moths. This competition may limit the size of cactus moth populations.  Researchers make sterile males by irradiating adult moths, which subsequently produce sterile offspring.

A crucial component to the success of SIT is the relative fitness of the sterile moths to fertile ones.  If the sterile moths are more fit, they will reduce the number of successful matings by fertile moths, thereby limiting the number of cactus moth offspring.

To determine whether the sterilized males would be viable competitors, Sarvary studied flight behaviors of cactus moths as a post-doctoral researcher after graduating with this Ph.D. from Cornell. He studied them in Zurich, at the Swiss Federal Institute of Technology in Zurich, to prevent the spreading of the insect further into the U.S.

Sarvary characterized flight distances, number of flights and seasonal effects on wild and lab-reared moths to understand whether sterile males could be seductive suitors in the wild.

The data comes at an urgent time for Mexico.

“There has always been some records from the coast of Mexico and from smaller islands in 2008 and 2009, and probably, we are going to see it in the mainland this year.”

Original Author: Daina Ringus