Munching Along

Out-of-towners flock to New Orleans for jazz, great food, and a chance to amble quaint, narrow streets overhung with wrought-iron balconies. What few tourists realize is that wherever they wander in this city, they’re probably within a few feet of hordes of invasive termites. Indeed, New Orleans–and especially its French Quarter–constitutes ground zero of the Formosan subterranean termite’s North American invasion, entomologists say. The insects are chowing down on wooden structures, from houses to living trees. Consequently, New Orleans has also become a central proving ground for new technologies to find and attack these especially aggressive and resourceful insects.

At least eight southern states, Hawaii, and southern California now host the alien termite known as Coptotermes formosanus. These insects create significantly bigger colonies–and, therefore, more damage–than do their native U.S. cousins, which reside underground and enter buildings only to forage.

Repellents and poisons work against the Formosan termites, but it’s difficult to select an effective location for placing baits. In contrast to native, subterranean termites, which always enter a building at ground level, the aliens may never cross the ground because they can reside within buildings or in trees. So, exterminators now need to conduct a three-dimensional search to locate nests.

Estimated costs to control C. formosanus and repair damage the insects have caused in the United States now run about $1 billion a year, says Alan R. Lax of the U.S. Department of Agriculture’s Southern Regional Research Center in New Orleans. In comparison, the much more widespread, native North American termites cost the United States $10 billion each year.

So far, the Formosan termite–long endemic throughout the Asian Pacific–has spread slowly since it disembarked at several southern seaports about 60 years ago. However, northerners shouldn’t be smug. This year, Xing Ping Hu of Auburn (Ala.) University found a colony in a part of Alabama where last winter’s temperatures dipped to –15F. That’s an environment, she says, that “previously we would have considered uninhabitable.”

This insect spreads via infested boats and shipments of landscape timbers, mulch, and potted plants. At the Society of Environmental Journalists’ annual meeting in September, Gregg Henderson of Louisiana State University in Baton Rouge argued that if infested boats and products aren’t detected and quarantined, Formosan termites could establish successful colonies as far north as Boston on the East Coast and Tacoma, Wash., on the West Coast.

Stealthy invaders

Biologists suspect that the 3/16-inch-long aliens arrived in North America during or shortly after World War II as stowaways in crates on troop ships returning from the Asian Pacific. It can take new colonies at least 7 years to reach a size that creates detectable damage. Indeed, these insects evaded detection for about 2 decades because they were mistaken for native termites of the Reticulitermes genus.

Eventually, New Orleans’ pest-control specialists realized that local termites, always a problem in that town, had started behaving strangely.

For instance, termites had begun hollowing out live trees instead of just dead ones. And some colonies actually nested in homes and other structures rather than just dining on them. Young adults also instituted a new ritual: flying in dense night swarms as millions of the newly fertile individuals sought mates and homes.

Smaller but similar infestations turned up in several other southern military-port cities, such as Charleston, S.C. Entomologists finally identified the insects as C. formosanus, a species that had for centuries destroyed wooden structures throughout the countries of East Asia.

Although native subterranean termites forage outside their nest for woody food, they return each day to their underground warrens to rest and bring nourishment to their colonies. Not so their alien cousins. If Formosan termites find reliable food and drink–such as framing timber and rainwater–they’ll permanently nest within a building’s walls.

Such an aboveground colony may come to light only when seemingly solid floorboards become squishy underfoot or a population overgrows its space and begins burrowing out through plaster walls. Some southern home owners have removed wallpaper to find large patches of wallboard and framing replaced with a vast span of cemented soil and feces, known as carton, housing many thousands of squirming, milk-colored termites.

Not neighborly

For the past 5 years, Matthew T. Messenger of the New Orleans Mosquito and Termite Control Board has been studying 18 colonies of Formosan termites living in a 31-acre park just north of the French Quarter. Each population, which typically consists of 500,000 to 3.5 million individuals, has proved genetically distinct. Huge squadrons of soldiers jealously guard a nest’s tunnels and chambers and patrol alongside the community’s foragers. To visually distinguish members of neighboring populations, Messenger fed them dyes that left many of the insects either red or blue for up to 6 months.

With this color-coding, Messenger established that Formosan termites are anything but neighborly. Unusually feisty under the best of conditions, the soldiers more aggressively attacked members of an adjacent population of its species than they did wandering individuals from a more distant Formosan colony.

Color-coding also helped Messenger gauge the difficulty in eliminating this pest. For instance, he provided poisoned food to three large colonies of dyed termites in the park last year and watched them completely die off within 3 months. However, only one of the several-acre nests became a ghost town. Within days of the initial poisoning, neighboring colonies of a different color sent squatters into the outer edges of the dying nests. By 7 months after the poisoning, Messenger reports, “one dead colony had been completely reinvaded.”

This confirms that eliminating the occasional nest can be pointless, Lax says. To be effective, he maintains, Formosan termite treatment must be administered widely and repeatedly.

That’s why his agency for 5 years has been spearheading a federal program known as Operation Full Stop. Its goal is to prove that if buildings and public lands in a broadly infested area–such as the French Quarter–are treated conscientiously, neighborhoods can empty mature nests and keep them vacant.

The problem is that New Orleans is a Formosan termite’s idea of heaven, Lax notes. Year-round, the weather remains warm and damp. Homeowners frequently permit moist, sheltering vines to blanket exterior walls and balconies. Adjacent buildings often share a wall, so as pest-control teams treat one building, a termite population can hide out next door, or even upstairs.

Messenger recently visited Hong Kong, where signs of the termite’s ravages appear everywhere, from boats to skyscrapers. In one luxury penthouse 23 stories up, Messenger recalls, “Formosan termites were eating maple flooring up to its lacquer finish, so you could actually see them running around under the lacquer.”

Then, there are the trees. Although a native termite colony might occasionally infest a tree, it’s almost invariably a dead one, Messenger says. When he began his studies in Armstrong Park, Formosan termites infested 251 of the park’s 708 apparently healthy trees. The 24 affected species included oaks, red maple, and redbud. Many trees in the park have since died or been treated. In most of New Orleans, the Formosan termite’s arboreal nesting comes to light only when a trunk gets so hollowed out that it snaps during a storm.

Stalking termites

The termites in New Orleans shun exposure to the elements, except for the few-hour span in their life histories when new adults swarm. USDA is evaluating several technologies to home in on the especially well-hidden Formosans. For instance, pricey infrared cameras can pick up spots in walls and trees where termite activity is generating heat.

Microwave systems–the entomologist’s version of the radar gun–bounce beams through building materials or trees. Where they hit moving objects, such as teeming termites, they register an anomaly. Pest-control operators can then drill into a wall and insert a fiberoptic camera, essentially a laparoscope, to confirm the insects’ presence.

Finally, several new acoustic systems are eavesdropping on termite noise. Explains Lax, there are subtle sounds when the bugs chew and tear wood fibers and when they bang along their tunnels (https://www.sciencenews.org/20031129/formosa1.wav). Even without auxiliary equipment, Messenger notes, “on a really quiet night, you can hear these guys munching around. And if you tap on a wall, they’ll bang their heads,” presumably drumming an alarm to nest mates.

For the past 2 years, Hu’s team at Auburn has been training dogs to sniff out Formosan termites. In field tests, they perform reliably both inside buildings and out, Hu says. Their primary limitation is that they miss Formosans in ceilings and high in walls.

No end in sight

Most people who have confronted Formosan termites would like to see them eliminated. However, “we can’t possibly do that,” says Frank S. Guillot, who coordinates USDA’s Formosan termite program. The invaders are too well established, so the best people can hope to do is to manage populations, he says. His group and others have begun intensively studying the insect to identify its vulnerabilities.

At the Entomological Society of America’s annual meeting in Cincinnati last month, Louisiana State’s Henderson reported making headway on understanding why colonies of this species have unusually high proportions of soldiers. In native subterranean termite populations, perhaps 2 percent of individuals mature into soldiers. The share in Formosan populations can be 20 percent, Henderson says.

Only termite soldiers develop what is called a frontal gland, a huge organ that secretes a signaling chemical, or pheromone. Henderson’s group identified six novel proteins and seven acids in the Formosans’ secretion.

In lab tests, the scientists showed that the secretion not only serves as an alarm but also as a biochemical stimulus for transforming more of a colony’s workers, which are immature termites, into soldiers.

The findings suggest a new strategy that exterminators might use for “messing up the colony’s structure,” Henderson says. If one or more elements of the secretion could be applied to baits, water, or infested soil, even a larger share of a colony’s members might become soldiers.

This could “put a potentially catastrophic drain on the colony,” he says, because soldiers, as the only sterile members of the population, don’t contribute directly to reproduction. Soldiers also don’t collect food, so increasing their ranks would put greater foraging demands of the remaining workers.

To date, most efforts to control Formosan termites have focused on poisoned baits and repellent treatments for vulnerable building materials. At the Cincinnati meeting, Henderson’s group reported new advances on both these fronts. For instance, the Baton Rouge biologists have isolated an oil known as nootkatone from the roots of a grass called vetiver. This woody-scented oil, which turned out to have been used commercially to add citrus flavor to sodas, repels Formosan termites for up to a year. The scientists also described isolating constituents of sesame oil that are both repellent and poisonous to Formosan termites.

Moreover, scientists have known that termites would follow a line drawn with ink. Henderson’s team has now isolated a component–2-phenoxy ethanol–that’s intoxicating to Formosan termites. One way to boost the efficacy of a poison is to add agents that lure termites to it.

Today’s termiticides use a food, such as cellulose, as a lure. However, Henderson says, a potent-enough nonfood lure, perhaps 2-phenoxy ethanol, could bait termites to a poison that wouldn’t offer any nutrition.

Maureen S. Wright, a member of Guillot’s team, is developing a biological warfare agent–the fungus known as Paecilomyces. Her colleague Mark Jackson at USDA’s research center in Peoria, Ill., has worked out a low-cost way to produce large batches of the fungus.

In field trials, Wright’s group drilled holes into infested trees and pumped in a liquid containing the fungus. It proved remarkably deadly; moreover, the fungus also grew inside the treated trees, suggesting that the treatment will last over extended periods.

The researchers made another promising finding when they detected foraging termites carrying the infection back home and sharing it with nest mates as they groomed each other. “Theoretically,” Wright says, this fungus “could control the entire nest.”

Several pest-control companies are now looking to license that just-patented biological-control system.

Control won’t come cheap

Excellent technologies already exist for fighting the Formosan termite’s U.S. advance, says Grady J. Glenn of Texas A&M University in College Station. The problem, observes this entomologist who for 20 years ran a pest-control company, is convincing exterminators to invest in costly technologies.

He notes that many companies resist buying a $300 device for detecting moisture, which usually signals a burgeoning termite colony or water leaks that can promote termite infestations. If companies view those meters as too expensive, Glenn says, what’s the likelihood they’ll spring for $10,000 infrared cameras or a microwave gun that has to be leased at several hundred dollars a month?

Under USDA funding, Glenn is completing the development of a computer-aided training program for the pest-control industry. His program aims to communicate the nature of the alien termite and value of the still-pricey tools needed to control it.

****************

If you have a comment on this article that you would like considered for publication in Science News, send it to editors@sciencenews.org. Please include your name and location.

To subscribe to Science News (print), go to https://www.kable.com/pub/scnw/
subServices.asp.

To sign up for the free weekly e-LETTER from Science News, go to https://www.sciencenews.org/subscribe_form.asp.