New weapon found in fight against leaf-cutter ants

Leaf-cutter ants can munch through ornamental vegetation, trees and garden crops overnight leaving naked branches.

They are the enemy of Costa Rican gardeners and farmers.

Long columns of the offending ants are easy to see as they carry leaf bits and other plant parts to their extensive underground homes.

There the ants chop up the vegetation further and inoculate it with a special fungus. Eventually, the colony will dine on the fungus crop that is produced.

Scientists say that a leaf-cutter colony, which can be more than 60 feet deep and hundreds of feet wide, often contains dozens of farming chambers and millions of worker ants.

Attempts to eradicate colonies generally fail because the ants make their own food from the fungus and they do not consume the poison that human neighbors spread about. During a walk through urban areas in the Central Valley expats can see places where white chemicals have been spread around the entry to the ant colonies. The ants also make highly visible little highways through the vegetation where they carry their pilfered vegetation.

There maybe some hope for aggrieved humans. A 15-year study of leaf-cutter ants and their relatives across North and South America found that their nests are susceptible to infection by a diverse group of specialized fungal parasites, according to Rice University in the U.S. state of Texas..

In addition to biologists from Rice, scientists from S“o Paulo State University in Rio Claro, Brazil, and the University of Texas at Austin uncovered new clues for controlling the agricultural and garden pests.

The study, which is available online in Royal Society Open Science, is one of the largest ever undertaken of parasites associated with leaf-cutter ants. It began in 2000 and involved collecting, cataloging and analyzing samples of parasitic fungi called Escovopsis from dozens of colonies of leaf-cutter ants and their relatives in Brazil, Argentina, Panama, Mexico and the Caribbean islands of Guadeloupe and Trinidad and Tobago. Researchers  identified 61 new strains of the fungi, which

A fungus-growing ant from the genus Trachymyrmex, the closest living relatives of leaf-cutter ants, tending to a fungal garden.

A fungus-growing ant from the genus Trachymyrmex, the closest living relatives of leaf-cutter ants, tending to a fungal garden.

attack the ants’ food source, said Rice university in announcing the study.

“Leaf-cutter ants are difficult to control with ordinary means, partly because they’re farmers,” said Scott Solomon, an evolutionary biologist at Rice University. “They don’t respond to most baits and poisons because they grow their own food, a specialized fungus that’s co-evolved with them in a symbiotic relationship for the last 50 million years.” He was quoted in a university news release.

Leaf-cutter ants inhabit areas from the southern United States to Argentina, and there are at least 40 species, and each leaf-cutter species has its own partner, the fungus that it grows and cultivates for food and that, in turn, depends on the ants for food and shelter, the university noted.

Solomon began collecting leaf-cutting ants and their funguses in Central America in 2002 as a graduate student. Solomon then spent a year working at S“o Paulo State in Rio Claro, Brazil.

The research revealed 61 new strains of Escovopsis, more than three times the number that had been cataloged in all previous studies. It also found that Escovopsis is more of a generalist than was previously thought. The same genetic variant was found invading the colonies of distantly related fungus-growing ant species, and as many as three different forms of Escovopsis were found in the same ant colony.

“Based on what we know so far, it could be possible to develop an Escovopsis-based control strategy in which a single form of the parasite could be used to target several different species of ant,” Solomon is quoted as saying by Rice University.

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