NC State Scientist Discovers Mosquito Repellent in Tomatoes

A substance produced by tomatoes repels mosquitoes and other insects more effectively and is safer than DEET, the chemical most commonly used in insect repellents, a North Carolina State University scientist has discovered.

Indeed, work by Dr. Michael Roe, William Neal Reynolds Distinguished Professor of Entomology at NC State, showed that the natural compound found in tomatoes is so effective at repelling insects that the university patented the substance. The patent describes how the substance may be used to repel insects.

The university has since licensed the right to produce the substance as an insect repellent to Insect Biotechnology Inc., a Durham company that specializes in developing and marketing biochemical insecticides. Funding for the research was provided in part by the National Science Foundation (NSF), the N.C. Biotechnology Center, the N.C. Agricultural Research Service, and Insect Biotechnology. Roe’s research was also supported by university overhead receipts.

Roe and Insect Biotechnology Inc. officials believe the substance, which Insect Biotechnology is calling IBI-246, has the potential to replace DEET as the active ingredient in most insect repellents.

“People have been looking for a competitive product to DEET for 20 years,” said Dr. John Bennett, chairman and CEO of Insect Biotechnology. “I think this is it.”

DEET (short for N, N-diethyl-meta-toluamide) is a widely used chemical. The U.S. Department of Agriculture developed DEET for the Army in 1946. The federal Environmental Protection Agency has registered approximately 230 products containing DEET, and EPA estimates that one -third of the U.S. population uses DEET each year.

While the EPA has found that the normal use of DEET does not present a health concern to the general population, the use of products containing DEET has been associated with rashes, swelling and itching, eye irritation and, less frequently, slurred speech, confusion and seizures. Products with high concentrations of DEET are considered hazardous to children particularly, and the EPA no longer allows claims on labels of products containing DEET that the product is safe for children.

Recent research at Duke University with rats showed that frequent and prolonged use of DEET caused brain-cell death and behavioral changes in the animals.

Roe said that like DEET, IBI-246 repels insects effectively and, on the scale used by the EPA to gauge toxicity, is considered slightly safer. He said he discovered the repellent capacity of IBI-246 by accident.

“I was listening to a scientific presentation about protein mimics as a diet pill for the control of mosquito larvae,” Roe said. He realized that the compounds being discussed were similar to a compound found in wild tomatoes that Roe and another NC State entomologist, Dr. George Kennedy, also a William Neal Reynolds Distinguished Professor, had studied a number of years earlier.

Roe and Kennedy had studied the compound, which apparently is part of the tomato’s natural defenses against insects, to see if it might be used to control worms that eat tomatoes.

Roe revisited the compound and tested it as a mosquito repellent.

He found that it not only repelled mosquitoes, but ticks as well. Bennett said subsequent testing has shown that the substance also repels fleas, cockroaches, ants and biting flies, as well as insects that are agricultural pests such as aphids and thrips.

Roe said the compound is already used to make cosmetics, so its toxicity has already been studied.

“What this means is that the toxicology has been done, which is a big step toward commercialization,” Roe said. “It’s found in tomatoes, it’s natural, it can be obtained organically, it’s safe and it’s at least as effective as DEET, all features that the public would want for a new-generation insect repellent.”

Roe added, “With the concern about West Nile virus and Lyme disease – spread by mosquitoes and ticks, respectively – in the U.S. and with the threat of other diseases like malaria outside the United States, people need the personal protection of insect repellents. And what about the nuisance factor of mosquitoes, ticks and flies?”

Bennett added that the cost of producing IBI-246 is expected to be competitive to the production cost of DEET.

Bennett said Insect Biotechnology has applied to the EPA for approval to use IBI-246 as an insect repellent in several products. While it is impossible to tell how long the approval process will take, Bennett said he is hopeful IBI-246 will win EPA approval by the end of the year.