Subterranean Termites: Battling the Swarms From Underground

Subterranean termites, slightly smaller than their drywood cousins but more numerous, cause the most destruction nationwide.

They live underground in colonies with 250,000 to more than a million inhabitants, tunnel up to feast on wood, and tend to swarm in search of new homes during the spring.

The workers are only a quarter of an inch long, UC Riverside entomology professor Michael Rust said, but the sheer force of a million munching mouths can cause considerable destruction over a period of several years.

The usual method of treating subterranean termites is putting a chemical barrier into the ground. This doesn’t eliminate the huge underground termite colony. While a treatment may kill the few termites that try to penetrate the barrier, it’s more like holding a cross in front of a vampire--he backs away and looks for another victim to bite.

So, the termites will turn their attention to a nearby tree stump, or maybe your neighbor’s unprotected house.

Protective chemical barriers can last five to 10 years or so if undisturbed. But natural settling of the soil, invading tree roots, earthquake damage and other factors can break the barrier and let termites slip through cracks into the house.

Until recently, chlordane and related chemicals were the choice for subterranean termite treatment. Chlordane lasts for 30 years. But health concerns about lingering chemical vapors led the EPA to ban chlordane use by exterminators after April, 1988.

Chlordane can damage the central nervous system and is suspected of causing cancer, although not all scientists are convinced of that.

Homeowners are allowed to use any remaining chlordane they may have, but EPA officials strongly recommend getting rid of it. If you have chlordane or another pesticide you no longer want, call the local agricultural commissioner for advice on how to safely dispose of it. Don’t dump it down the drain or in the trash, because it could end up in the water supply.

Exterminators now use chemicals that don’t last as long, so houses have to be treated more often. The four most commonly used in California are chlorpyrifos, cypermethrin, permethrin and pydrin, marketed under various brand names, said Jerry Campbell of the state Department of Food and Agriculture. There may be some odor after they’ve been applied, which should eventually disappear.

The most effective use of the chemicals is to treat a site before the house is built, rather than trying to dig around it afterward, or drill through the slab, said John Munro of the Pest Control Operators of California, the industry trade group. Treatment after the house is built usually costs $600 to $1,200, said Orkin spokeswoman Judith Donner.

Most new houses in Southern California are built on slabs directly over the ground, which makes it difficult to reach the soil below. Some older houses have a crawl space underneath, so soil can be treated directly.

A number of California builders routinely pre-treat building sites. Not only do some construction codes require it, it’s cheaper to spend $40 on a pre-treatment than spend more to fix a problem later, said Eric Elder, Kaufman & Broad’s director of marketing. Their home sites are pre-treated with Dow’s Dursban TV (chlorpyrifos), the leading chlordane replacement.

Pre-treatment is especially important if you’re building on an area already infested with termites.

Munro recalls houses built in the 1970s on the site of an old citrus grove, without pre-treating the soil. Within a year, most of the homes were invaded by subterranean termites that had been living off remains of the former orange trees. Skipping a $30 pre-treatment cost residents $400 afterward, and they sued the builder.

A pre-treatment method getting renewed attention involves covering the site with fine-grained sand that termites can’t travel through. Ebeling studied this method in the 1950s but no one was interested then, Rust said, because chlordane was in such favor.

The sand method is recommended by the National Coalition Against the Misuse of Pesticides, a Washington, D.C.-based nonprofit group that fought against chlordane. Sand and metal termite shields on buildings make it much tougher for the insects to get in and are better than repeated doses of chemicals to maintain a barrier, said Susan Cooper, staff ecologist.

With pesticides, “you’re poisoning your whole house and you’re not killing termites,” she said.

Another non-chemical method of attack for subterranean termites is releasing nematodes into the soil. Nematodes are tiny worms that can kill termites. However, research has not found nematodes to be effective in controlling colonies of subterranean termites, said Joe K. Mauldin, principal entomologist at the U.S. Southern Forest Experiment station in Gulfport, Miss. They might kill some termites but not enough to prevent them from damaging a house, he said.

But Jay Tallon of Tallon Termite and Pest Control said he has found nematodes effective if used properly. Soil texture and moisture affect how well the nematodes do their kamikaze mission--they die after killing the termites, he said. The nematode treatment costs about $700.

Scientists are working on other methods, too.

Termites can be treated with a slow-acting poison that eventually kills most of the colony, said Glenn Esenther, a Madison, Wis., consultant. He puts out cardboard bait--”it’s like chocolate cake to them”--and a few days later dusts the resulting termites with insecticide, which they take back to their nest and share.

University of Florida researcher Nan-Yao Su is experimenting with insecticide-laced bait buried in the ground. Unlike current methods, such treatment could kill most of the termites in a nest, he said, although it might take a month or two. Another advantage is that it uses far less pesticide. He said it could be several years until the bait is available commercially.

Su said he anticipates some resistance from exterminators using traditional applications of gallons of chemicals, although the two methods could be combined.

Mauldin said researchers are also looking at new ways to treat wood to make it taste bad to termites.

In addition to the above methods, there are some do-it-yourself termite treatments on the market, including soil treatment for subterraneans and spot chemical treatments for drywoods.

But it’s not a good idea for homeowners to try handling the problem themselves, EPA pest management specialist Bill Currie said.

Even if they correctly figure out which type of termite is eating their house, homeowners don’t have the right equipment. Chemicals used to discourage subterranean termites are hard to apply properly without special tools to penetrate the soil beneath a house, he said.

And some do-it-yourselfers ignore instructions, figuring if a little bit is effective, twice as much would be even better. Although pesticides sold to homeowners are not as potent as those available to pest control operators, it’s still possible to overdo it.

SOURCES OF TERMITE CONTROL INFORMATION The following organizations and services offer information on termite control:

* Structural Pest Control Board

1430 Howe Ave.

Sacramento, Calif. 95825

(213) 620-2255 or (916) 920-6323

Regulates California pest control industry. Provides consumer information and handles complaints against pest control operators.

* National Pesticide Telecommunications Network

(800) 858-PEST

24-hour hot line at Texas Tech University Health Sciences Center School of Medicine. Funded by EPA and Texas Tech. Answers questions about pesticide use and safety, symptoms of pesticide poisoning and cleanup and disposal procedures. Also gives referrals for emergency treatment and investigation of pesticide problems.

* USDA Southern Forest Experiment Station

Room T-10210, IPS

USPS Building

701 Loyola Ave.

New Orleans, La. 70113

(504) 589-3935

Does termite research for USDA. Offers free 36-page, illustrated booklet “Subterranean Termites--Their Prevention and Control in Buildings.” Discusses good building practices and various control methods.

* Bio-Integral Resource Center (BIRC)

P.O. Box 7414

Berkeley, Calif. 94707

Nonprofit group that reviews latest research and recommends least toxic methods of pest control. Send $1 for “Least-Toxic Pest Management Publications Catalogue,” which has an extensive list of material on termites and other pests.

* National Coalition Against the Misuse of Pesticides

530 7th St. S.E.

Washington, D.C. 20003

(202) 543-5450

Nonprofit group that provides information on pesticide toxicity and recommends alternative pest control treatments.

* Cooperative Extension

Call your local Cooperative Extension office for pesticide information in your area. (Usually listed in the county government section of the telephone book.)

* The Environmental Health Coalition

1844 3rd Ave.

San Diego 92101

(619) 235-0281

Works to reduce the use of pesticides in home and urban environments. Has information on alternatives to toxic termite control.