FORT COLLINS-- A Colorado State University scientist's discovery may lead to a safer and cheaper way to prevent termites from infesting homes, where they cause an estimated $750 million in damage in the United States annually.
Entomologist Louis Bjostad found that termites' natural reliance on carbon dioxide to find food and shelter can also be used against the insects as a non-toxic alternative to current forms of pest control.
"When we first initiated the experiments, we wondered if the concept would be too simple to work," Bjostad said. "Our findings show that carbon dioxide undoubtedly attracts termites, which opens up a whole range of possibilities for controlling these pests."
Bjostad, with researchers Elisa Bernklau and Erich Fromm, made the discovery by placing two species of termites--Reticulitermes tibialis, a species common to Colorado, and R. flavipes, a frequent pest in the Great Lakes--at one end of a T-shaped tube. In one arm, researchers pumped in normal air, and in the other, CO2 in concentrations higher than those in normal soil.
"When a termite came to the point of choosing an arm, it moved its antennae to one side of the tube, then the other," Bjostad said of the experiments. "Most of them chose the side containing the carbon dioxide."
Bjostad and his colleagues believe termites are naturally attracted to carbon dioxide for two reasons. Rotting wood--the termites' main source of food--releases CO2, a process that likely guides the insects to food. Concentrations of the gas inside termite colonies is higher than ambient air, suggesting termites also use CO2 to find home.
Now Bjostad and his colleagues are using the discovery to create a substance that slowly releases CO2 underground to lure termites away from houses and other structures where they cause damage. Because it occurs in abundance naturally, CO2 offers an inexpensive, non-toxic alternative to current methods of pest control, Bjostad said. Environmentally-friendly insectides now in use are designed to pass from one termite to the other, but don't always do the job. As a result, pest controllers often resort to other toxic chemicals to eradicate termites.
Chemical companies have expressed interest in the finding, Bjostad said, in part because of the high costs to register new insecticides and chemicals. In-depth efficacy and public health studies and other research--costing an average of $50 million--must be submitted to federal agencies before a chemical company can manufacture and sell a product. Because CO2 is a natural gas, those costly studies would not be necessary, Bjostad points out.
Bjostad believes the CO2 discovery opens the door for a number of uses, such as luring termites to monitoring traps or to sources of insecticides. Slow releases of CO2 could also be used to confuse termite behavior to the point where a colony cannot sustain itself. The breakthrough even may have applications in new home construction.
Bjostad's lab plans to conduct experiments with other termite species common to the United States to determine what range of COs is effective on all species. Because the basic biology of other termite species is very similar, the Colorado State researchers expect little difference in their reactions. The initial termite studies were funded by the Colorado Agricultural Experiment Station.
This latest breakthrough was prompted by other research under way in Bjostad's lab. Last year, the Colorado State team showed that western corn rootworm--a pest that causes $1 billion in crop damage each year--solely uses CO2 to find young corn roots. Larvae must locate roots within three days after hatching or die of starvation. Bjostad developed several pellets containing natural ingredients that slowly release the gas. The pellets, buried at corn planting time, steer rootworm larvae off-course.
Bjostad's recent discoveries with termites and rootworm points to the possibility that many soil-borne insects also rely on CO2 to locate food and shelter. If so, the gas could be used to steer other agricultural and household pests away from places they do harm.
"Manmade insecticides assume the pests will come into contact with the chemical and die," Bjostad said. "This is a case where we're using the pests' own genetic predispositions to elements that already exist in nature to change their behavior or lure them to their deaths."