Liquid sprays don’t control large subterranean termite colonies as well as baits, giving more credence to the benefits of baits as a way to minimize the bugs’ damage to structures, a new University of Florida study shows.
Formosan and Asian subterranean termites are responsible for most of the $32 billion in economic damage to structures worldwide, UF Institute of Food and Agricultural Sciences researchers say.
Through the years, there has been some debate as to whether exterminators should use CSI baits or liquid termiticides – the sprays used to control subterranean termites, said Thomas Chouvenc, a UF/IFAS assistant professor of entomology. Scientists call termite baits “chitin synthesis inhibitors” (CSI) because of their chemical makeup.
“The problem with Formosan and Asian subterranean termites is their large colony size and underground foraging abilities. With liquid termiticide treatments, only a small fraction of the colony is actually affected, and more critically, termites can sometimes find their way around the chemical barrier,” said Chouvenc, a faculty member at the UF/IFAS Fort Lauderdale Research and Education Center. “Therefore, if the colony is not eliminated, the potential for damage is still there, because the treatment may just kick the can down the road.”
Unlike liquid termiticides, CSI baits can eliminate colonies, no matter how far the colony nest is from the treatment, the new research shows.
Scientists thought termites could not detect non-repellent liquid termiticides. If termites pass through non-repellents, they are killed by contact with the chemical. However, the UF/IFAS study shows that termites die so fast that only the termites near the treatment are killed. With the accumulation of dead termites near the treatment, the rest of the colony avoids the treated area and survives.
Previous laboratory studies showed benefits of both treatments, however they only used small groups of termites and unrealistically short distances, Chouvenc said. Therefore, he wanted to test the efficacy of non-repellent termiticides versus CSI baits on whole colonies and long distances.
For the study, Chouvenc used about 780,000 termites from 12 colonies, each about 12 meters away from a simulated house. Non-repellent termiticides and baits were each placed about 6 meters from the “house.”
Chouvenc evaluated the effect of liquid termiticides and CSI baits for three months, and determined their impact on whole colony survival and the termites feeding activity at the house.
To simulate ways a termite could get into a building and how they find their way around the treatment, Chouvenc gave termites different access points to the house through a complex network of arenas. If termites found their way around liquid termiticides, the damage continued. With baits, even if they found a way around, they all died, and the damage stopped.
When Chouvenc simulated field conditions and used liquid treatments on the termites, only the exposed part of the colony was harmed by the pesticide, while the rest of the termites survived, said Chouvenc. Therefore, liquid termiticides may only temporarily limit the access to the structure for termite colonies. They may not eliminate them, he said.
“With CSI baits, if a part of the colony feeds on the baits, then the whole colony is doomed,” Chouvenc said. “In addition, by maintaining the baits around a structure over time, especially in areas with high termite activity, all new termite colonies foraging around the structure will be exposed and eliminated even before damaging the structure.”
The new study is published in the Journal of Economic Entomology.