03/19/2024

Swarmer Season: What’s happening, why and how long will it last?

John Singletary, ACE, Nisus

After two to four years of growth, a subterranean termite colony has matured enough to begin producing male and female termites that leave the nest in reproductive flights or swarms. Common misconceptions are that the warmer temperatures of spring and summer usher in the so-called “swarmer season”, but this is misleading because termite colonies can be active year-round.

While spring is the most common time of year when alates (winged reproductive caste members) take flight to mate and begin new colonies, this phenomenon is not isolated to Subterranean termites. Many ant species will also swarm this time of year, and to the untrained eye, this can cause confusion as ant swarmers and termite swarmers look very similar. For the simple eyeball test and ID, once the alates of both ants and termites mate, they will drop their wings. Knowing the difference between the two types of wings, termite wings are of similar size and venation (vein structure) whereas ant alates’ wings are of two very different sizes and structures, which can make the identification process easier.

Subterranean termites often begin their reproductive flight or “swarm” when temperatures begin to warm, and the humidity begins to increase with the spring showers. Warmth is the first condition that stimulates an elevated level of activity within the nest. Whether it is the warmth of the ground created by direct exposure to the sun, or the indirect warming of the southern sides of structures resulting from the solar track of the sun. This activity pattern differs from that of Drywood termites may forage year-round, subterranean termites are affected by temperature.

For subterranean termites, the alate or swarmer activity in the Mid-Atlantic region can begin as early as late February and extend into the Memorial Day weekend in May. With temperatures influencing termite activity, the following is a general rule of thumb of how seasonality affects activity.

• Foraging and Exploring - 70-90F (degrees)
• Nest Building and Expansion - 65-85F (degrees)
• Swarming Flights - 55-75F (degrees)
• Metabolism Shuts Down (diapause) - Below 50F (degrees)

While Spring weather does ramp up termite activity in the Mid-Atlantic, the key activity driver year-round is moisture. For termite populations to grow and thrive, high humidity levels are essential. This is why the mud shelter tubes and enclosed passage to and from the colony are essential. Low levels of humidity will rob their bodies of the essential moisture, they will desiccate and die. While they are destructive and hearty eaters, they are a fragile organism that is extremely moisture-dependent. Additionally, excessive wood moisture content can increase the nutrient levels in the wood (nitrogen) making the wood more palatable for the WDI.

Don’t sleep on STT elevated activity in the summer. This elevation in activity can occur in irrigated yards or other areas that are providing the moisture that may be missing in the July-August heat. Pay particular attention to moisture-heavy areas caused by malfunctioning or leaking irrigation or downspouts that cause moisture to pool near or around a structure.