Thursday, May 10, 2007

Where have all the fire ants gone?

Fire ants are evil incarnate. They are a horribly invasive species that have conquered the entire southern U.S. since their accidental introduction into Alabama from Brazil in the 1930s. They are a major reason the horny toad (Texas horned lizard) is a threatened species, since they devour the lizard's eggs and drive out red harvester ants that are the horny toad's diet. They also blind newborn calves and deer with their stings, are devastating to ground nesting birds and hurt like hell when they bite you. I spend a good bit of money every year on Amdro fire ant bait to keep them under control in our yard.

Last year after one particular series of heavy rains, the wife and I counted 22 mounds that popped up in our yard overnight. That's the pattern with fire ants--rain is the big revealer, and they flourish in wet conditions. We've had heavy rains moving through the area at least once a week for the past month or so, and the Blaschke household has been bracing for the coming invasion. A friend of ours lives 15 miles away in Seguin, and she reports that the infestation is out of control--dozens and dozens of mounds popping up faster than they can be treated.

But that, strangely enough, hasn't happened here. In the past three weeks, I've spread bait out over a total of four mounds, and none of them are what I'd characterize as huge. The ants are still around and as vicious as ever--I have three blisters on my foot from this afternoon's encounter as testament--but there just aren't that many of them now. Why is that? Maybe, just maybe, an experimental program begun last year to introduce a South American fly that uses fire ants as larval hosts is beginning to have a real impact:
"We've been releasing a different type of phorid fly in New Braunfels to see how effective it will be in the controlling fire ants," said Molly Keck, Extension entomologist for Bexar County. "We're hoping this one will be even more deadly to them than the other species of phorid fly we've been using throughout the state for fire ant management."

If the release is successful, additional releases of the new phorid fly species will likely be forthcoming, she said.

Phorid flies kill fire ants by "dive-bombing" them in order to lay their eggs in the ant's thorax, Keck explained. Once hatched, the fly larvae migrates into the head of the ant, eating the contents. Eventually, the ant's head falls off.

The new fly, Pseudacton curvatis, is imported from South America and has been acquired though the U.S. Department of Agriculture's Animal and Plant Inspection Service, Keck said.

Well, that's interesting and all, but how do I know that we're even in an area where these flies would be around to work their magic?
An initial release of about 75,000 of these flies was completed over three days – June 14, 20 and 23 – in the southeastern part of the city.

"This type of phorid fly is different from the Pseudacton tricuspis, which is already being used in several counties as a biological fire ant control," Keck said. "It's more robust and prefers the smaller-sized worker ants. It also handles cold weather better than tricuspus, so it's less likely to die out during fall or winter."

The new fly's aggressiveness toward smaller worker ants is especially useful in eliminating fire ant colonies with multiple queens, Keck said.

"Those colonies usually have large numbers of the smaller worker ants in and around them," she said. "So they provide more ‘targets' for this fly. And these types of colonies are abundant throughout the state."

Our subdivision is literally at the southeastern tip of New Braunfels. I can walk across the street and move out of city limits. We are surrounded on four sides by farmland and cow pastures, and on summer days you can look over the green fields and see the grass broken by brown fire ant mounds every 5-10 feet or so. The flies are here, and they're working. To which all I can say is "yay!"

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