STARKVILLE, Miss. (WJTV) – Invasive Formosan subterranean termites are expected to swarm soon and threaten unprotected structures in about one-third of Mississippi’s counties.

Santos Portugal, Mississippi State University (MSU) Extension Service urban entomologist, said Formosan termites typically swarm in the millions from early May to early June. They have the ability to infest and significantly damage structures much more quickly than native subterranean termites.

“Swarming Formosan termites are reproductive, winged alates that go out on mating flights from established colonies,” Portugal said. “They pair off, mate, detach their wings and look to establish a new colony.”

Like the native Eastern subterranean termites, they typically infest structures from the ground, but Formosan infestations also can occasionally arise from a mated pair of swarmers finding moist wood on a roof or above ground.

“If a colony starts this way, traditional soil-based termite preventative treatments are not effective,” Portugal said.

Formosan termites were first discovered in Mississippi in Lauderdale County in 1984. Portugal said they are considered established in at least part of 26 primarily southern counties, but they potentially can be encountered anywhere in the state.

“There have been Formosans collected from or near Starkville, Columbus, Louisville, Olive Branch, Tupelo and Oxford within the last decade, but these appeared to be isolated cases, and it is not known if Formosans are truly established that far north,” he said.

Formosan swarmers are about one-half inch long, including their wings, and are yellow to golden brown. Native subterranean termite swarmers are smaller and are dark brown to black in comparison.

“When a Formosan colony is established in a structure, their swarmers will often emerge indoors from what is known as a swarm castle,” Portugal said. “These irregular spots of dry mud can appear overnight in late spring and are often found on the ceiling or higher up on walls. Established colonies can develop a carton nest which allows them to sever their connection to the soil for moisture, making them more difficult to find and treat.”

Outdoors, Formosan colonies can be enormous, containing more than a million termites over an area the size of a football field or larger. They also actively infest live trees, weakening limbs and trunks.

Another difference between Formosan and native termites is that Formosans swarm at night and are highly attracted to light. Native subterranean termites swarm during daytime hours, usually in mid-February to mid-May.

A termite contract with a reputable pest control company includes an annual inspection for termites by a pest management professional and additional needed treatments at no extra cost.

“The best way to protect your home or building from termites is to be sure it has been preventively treated for termites and that the termite treatment is current and nothing has happened to compromise its effectiveness,” Layton said.

Contracts differ between companies, and it is important to understand what is outlined in the agreement before committing.

“Not all companies cover Formosan subterranean termites in their contracts,” he said.

Many structures use spray foam insulation, but experts warn this can hide leaks and termite activity, potentially resulting in extensive damage before an infestation is detected.