New compound promising for termite, mosquito control

LSU AgCenter researchers have developed a new compound that holds promise for controlling termites and repelling insects — particularly mosquitoes.

The chemical, tetrahydranootkatone, is a derivative of nootkatone, a substance the researchers earlier discovered both repels and is toxic to subterranean termites.

The LSU AgCenter filed a patent application earlier on nootkatone, a compound initially extracted from the oils of vetiver grass. Now the AgCenter recently filed a patent application on tetrahydranootkatone, which appears to be even more potent than the original compound.

The new compound was developed by Dr. Gregg Henderson of the LSU AgCenter's Department of Entomology, Dr. Roger Laine of the AgCenter's Department of Biochemistry and research associate Betty Zhu.

“We started looking at derivatives of nootkatone and found tetrahydronootkatone,” Henderson said. “We looked at slight changes in the structure of nootkatone. You never know if you'll find something better.”

Tetrahydranootkatone is up to 10 times more potent than nootkatone, he added.

In addition to termites, the researchers looked at the chemical's effect on other insects and tested tetrahydronootkatone on mosquitoes.

Henderson and Dr. Mike Perich, an LSU AgCenter entomologist, tested a 5 percent solution of tetrahydranootkatone over a three-hour period. Each applied the chemical to one arm and then put their arms in a cage of mosquitoes for three minutes at a time.

“The three-minute control versus the treatment showed significantly less effect,” Henderson said. “Most natural products like citronella usually give about 15 minutes of control. But the tetrahydranootkatone lasted three hours.”

Henderson said tetrahydranootkatone appears to prevent transmissions of nerve impulses from one nerve cell to another or to a muscle and, in effect, anesthetizes the insect.

In laboratory tests on ticks, which transmit Lyme disease as well as other maladies, the chemical has been more effective and longer lasting than DEET — the most common insect repellent currently in use.

“Tetrahydranootkatone could be an additive to other repellents to enhance them or incorporated into creams or lotions,” Henderson said. “But people can't go out and buy it today,” he added, noting a commercial company would have to license the compound and develop it for market.

LSU AgCenter researchers have continued working with nootkatone as a wood and soil treatment to inhibit or kill subterranean termites.

“It's a natural product,” Henderson said, adding it could create an effective barrier in the soil with regular applications at low concentrations.

“We also know nootkatone will kill termites in its gaseous state, and it has low volatility like mothballs,” Henderson said. “It also may be usable against other household pests such as moths and carpet beetles.”

LSU chemists are exploring ways to synthesize nootkatone to make it less costly to use as a wood treatment to control termites.

More research must be done before the product can be brought to market, the inventors said.

“This has potential, but it needs to be tested,” Henderson said, stressing, “No one product will solve the termite problem. We need an integrated pest management approach,” he added.

Funding for the research with nootkatone and its derivatives has come from grants from the U.S. Department of Agriculture and from the state of Louisiana.

Rick Bogren writes for the LSU AgCenter.

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