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COLUMBUS, Ohio - A naturally occurring fungus used as a biopesticide may have some application in controlling tick populations.
Ohio State University graduate student Ken Cradock is studying American dog ticks, collected in natural parks around the state, to determine whether the arachnids harbor Beauveria bassiana. Cradock is hoping the ticks contain a strain of the fungus that is pre-adapted to killing ticks. Strains of the fungus currently exist as an active ingredient in greenhouse and outdoor pesticide products that target specific adult and larva insects, such as mosquitoes and flies, and eggs of lepidopteran pests, such as moths.
"Studies done around the world have shown that strains will kill certain insects, so it's possible that a strain exists that is lethal to ticks," said Cradock. "If we find that strain, then it will add a further component for IPM of ticks." Beauveria bassiana strains control an insect by growing on it, secreting enzymes that break down the insect's cuticle, or outer coat, then enter the insect and continue to grow until they kill it. "It doesn't have the knock-down effect of chemicals. It takes some time for it to work," said Cradock. "But the fungus is a much safer pesticide to use than chemicals and is much more environmentally friendly." The Environmental Protection Agency (EPA) recognizes strains of Beauveria bassiana as safe and effective biopesticides. The organization has approved their use on ornamental plants, turfgrass, and food and other crops grown outdoors or in greenhouses. There are no health risks to humans who apply the biopesticide to crops or eat foods sprayed with the product, and it is not toxic to mammals, birds or plants.
Cradock, with the help of OSU acarologist Glen Needham will be collecting ticks throughout the season until the first frost. They will be observing whether the ticks show signs of infection. "On a high estimate, we expect to find three percent of ticks infected with the fungus, and then we have to determine if the strain is what killed the tick, or if another factor was involved," said Cradock. Depending on the success rate, Cradock expects to spend the next three years searching for the strain, collecting about 1,000 ticks a year.
Needham said that he and other OSU researchers are studying additional methods of tick control, including a tick's diapause, or period of inactivity during the season. "Tick season usually runs from mid-April through July, after which the ticks go into some kind of hibernation and are no longer actively feeding," said Needham. "We want to see if the tick has a diapause gene or not." Studies have also shown that ticks tend to migrate to grassy areas along roadways late in the season. Needham speculates the ticks are attracted to the large vibrations made by passing cars, thinking it's a big meal. "If we can determine that's what they are actually doing, then spraying along roads might also be a good method of control."