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Leaf-Cutting Ants on a Rampage in South Texas

- by Rod Santa Ana III, (956) 968-5581,r-santaana@tamu.edu

WESLACO -- For some reason, leaf-cutting ants in South Texas are much more prevalent this year than most. Homeowners, citrus growers and now even cotton farmers are complaining that the ants are mercilessly stripping their plants of leaves.

Dr. Victor French, an entomologist at the Texas A&M-Kingsville Citrus Center at Weslaco, thinks the increased activity may be drought-related. But whatever the reason, the ants are on a rampage, and there aren't many products available to treat them.

"We're working on the registration of a couple of products for use by farmers, but homeowners are somewhat limited in the number of products available to them," French said.

The scientific name of the Texas leaf-cutting ant is Atta texana. Their sting can be quite painful, but the ants are especially bothersome to humans because the nocturnal foragers can completely strip plants, even large trees, of their leaves. They carry the leaf bits into their nest where they feed on a fungus that grows on those leaves, called fungal gardens.

Leaf-cutting ants live in a highly structured society, French said. The queen is the reproductive center of the colony, which can have up to five queens. Most eggs laid by the queen develop into sterile female workers.

The workers, he said, vary greatly in size. The large workers are soldiers that protect the nest. Medium-sized ants forage for plants and dig tunnels and chambers, while the smaller ants maintain the fungal gardens and take care of the young ants.

Underground, tunnels and chambers can extend as deep as 7.6 metres. French said he has seen a leaf-cutting ant mound that had about 200 entrance holes, was about 1.22 metres tall and covered an area of about 112 square metres.

"For the first time in my career, I've gotten reports recently that these ants are now damaging young cotton plants. It could be that because of the drought, the ants are being forced to forage more to find alternative plant sources," French said.

Citrus pulp, made from the peel and other tissue that remains after citrus has been squeezed of its juice in juicing plants, is very attractive to leaf-cutting ants. The dried pulp is made into small pellets that are treated with chemicals toxic to ants when consumed. Ants carry the bait down into their nests to be eaten by all.

One such product commonly used here is called Volcano, which is produced in Mexico. But French said it would soon be pulled off the market.

Another product, Blitz, is also formulated with citrus pulp. It is effective for long periods of time, French said, but the product has not yet been registered by the federal government for use.

"We're testing several compounds, but at this point there isn't much on the market for either farmers or consumers," French said. "Farmers can use Lorsban in spray or granulated form, but its effectiveness is not long-lasting."

An ant bait product, Over 'n Out, is found in many stores and is fairly effective on leaf-cutting ants, French said, although its label touts it as a product mainly for fire ant control.

Another product French recommends for homeowners, although not too enthusiastically, is Grants Ant Bait.

"And there's a product called Bug Juice, which is available on the Internet," French said. "This product repels and kills leaf-cutting ants on contact."

* Article originally from http://agnews.tamu.edu/dailynews/stories/ENTO/Mar2905b.htm

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