Parasitic wasps keep flies at bay at Del Mar

By: HEATHER HENTER - For the North County Times | Saturday, June 3, 2006 7:37 PM PDT ∞

On July 19, horse racing fans will flock to Del Mar for opening day. Women will wear large hats, the "ponies" will thunder down the track, and money will be won and lost. And very tiny insects will make the whole experience pleasant.

Del Mar, along with racetracks across the country, use wasps to keep flies from overwhelming the place.

Every summer, Del Mar is home to 2,300 horses. All those animals produce a lot of manure, and all that manure attracts a lot of flies. Plant Superintendent Robert Sanchez said the racetrack used to control flies with chemical insecticides, but there was always a worry about horses getting sick. So for more than 12 years, the Del Mar track has been using a technique called biological control.

In biological control, living organisms, such as parasites, diseases or predators, track down and kill pests, such as flies. The wasps that the racetrack uses are not the huge yellow jackets that ruin a picnic; they are parasites of flies. In the 1979 sci-fi movie "Alien," a space creature invades John Hurt's character, Kane, and destroys the unsuspecting Kane from the inside out. The parasitic wasps at Del Mar work much the same way. A female wasp lays her eggs inside a fly, and when the wasp eggs hatch, the fly becomes lunch.

While parasites from outer space made for a spine-tingling chase scene with actress Sigourney Weaver, the real parasites here on Earth are much less threatening. They are small, no bigger than a bread crumb, can't sting, and have no interest in humans. But they are, unwittingly, fighting on our side. These are working wasps, and with the help of maintenance crew member Art Senteno, they will be working behind the scenes at the Del Mar Fairgrounds this summer.

During the race season, the stable area of the fairgrounds is a busy place, clearly focused on pampering a lot of very valuable horses. Clean horse blankets and leg wraps hang on laundry lines, flapping in the breeze. Straw and manure piles sit neatly outside the buildings; each horse stall is cleaned out at least twice a day.

Every Wednesday, a box filled with white paper bags, slightly larger than lunch bags, arrives at the track. The bags are filled with a mixture of sawdust and parasitized fly cocoons, cocoons that now contain a carnivorous wasp rather than a fly.Ý

Senteno is in charge of distributing these wasps. With this box of bugs tucked into the back of his golf cart, he drives to each pile of straw and manure, and sticks a handful of wasp-laced sawdust into the bottom of the pile. The adult wasps soon emerge from the fly cocoons (not as spectacularly as in the chest-busting scene in "Alien," but equally deadly), and the female wasps search out other flies in which to lay their eggs.

Those paper bags filled with wasps come from an Arizona company. Rick Frey started Arbico Organics in the late 1970s while he was a high school biology teacher.Ý

"I had summers off," he says. "I started growing bugs."Ý

Growing bugs is now a multimillion-dollar business for Frey. The exact way he rears the insects is a closely guarded proprietary secret, but his company, the largest supplier of fly parasites in the country, is big enough to keep a staff of 25 people very busy 365 days a year.

Frey sells wasps to most of the major tracks in the U.S., including Churchill Downs, home of the Kentucky Derby. The track superintendent, Butch Lehr, has been using Frey's parasites since 1983. "It works," Lehr says. "I remember how it used to be. You couldn't get out of your car without 10 flies landing on you."

He wasn't so sure about the wasps in the beginning. Trainers of racehorses can be as high-strung as their charges, and Lehr was not about to upset the delicate harmony at his track. So when Frey convinced him to try the parasites, Lehr decided to release the wasps on a Sunday, when no one was really looking. But he couldn't just quit spraying insecticides, without having trainers assume the worst. So for an entire season, Lehr's crew dutifully made the weekly rounds of the stables with their pesticide spray rig. But they filled the rig with plain water.Ý

"Anything people wanted us to spray, we'd spray," says Lehr, in his Louisville, Ky., drawl. "We sprayed anything that moved."Ý

Meanwhile, the wasps were going about their business, laying eggs and destroying flies. And there was no fly problem that season, despite the complete absence of chemical insecticides.

Lehr sounds like a successful graduate of a 12-step program when he says, "We might not be here today if we were still using (chemical insecticides)."

Del Mar's biological control and manure management program has been equally successful. Maintenance crewmember Senteno has worked at Del Mar for 26 years. In his early days, he says, flies were everywhere. When he told people he worked at the racetrack, their reaction was always, "Oh God, the flies," he recalls. He stopped telling people where he worked. But there is no need for such discretion now. During the race season, Del Mar releases 3 million parasites every week. And as any race fan will report, there are no flies.

FAST FACTS

For more information about Arbico Organics, see: store.arbico-organics.com/

For general information about biological control, see the University of California's Web site: www.ipm.ucdavis.edu/index.html