Nov. 11, 1997 ITHACA, N.Y. -- Scratching the surface of wild tomatoes that bugs don't bother, Cornell University scientists discovered the plants' chemical secret for repelling insect pests: a complex, waxy substance that commercially grown tomatoes have "forgotten" how to make.
A simplified formulation of the wild tomatoes' chemical has been granted a U.S. patent on "Non-cyclic Esters for Pest Control" and could become the next-generation nontoxic insect repellent for a long list of crops on hungry bugs' menu.
The newly patented compounds may work, in part, because they create sticky surfaces that insects don't like, and also because the compounds break down to release short-chain fatty acids, which are known to repel insects.
"We've made smaller versions of natural fats that are easily biodegraded to fatty acids," said Bruce Ganem, a Cornell chemist and co-inventor, along with Martha A. Mutschler, professor of plant breeding. "These are similar in structure to the natural triglycerides in our bodies, only with shorter fatty acids, and the amounts that will be on crops seem unlikely to pose a health hazard to humans." Ganem is the Franz and Elisabeth Roessler Professor of Chemistry in Cornell's College of Arts and Sciences.
Two insect larval pests, the tomato fruitworm (Helicoverpa zea) and the beet army worm (Spodoptera exigua), cause an estimated $30 million a year in damage to the processing-tomato crop inin California. The grubs bore holes in tomato fruits, allowing decay organisms to enter the skin and spoil the fruit. But when the Cornell pest-control chemical is sprayed on tomatoes, damage from tomato fruitworm and beet army worm is greatly reduced or eliminated altogether.
In addition to tomatoes, the patented chemical agents are expected to protect a wide range of crop plants and ornamental plants against more than 30 kinds of mites, beetles, leafminer flies and whiteflies, aphids, leafhoppers, mealy bugs, worms and thrips, the Cornell inventors said. And the same insect species that are repelled from eating the plants also are less likely to oviposit (lay eggs), thus breaking a cycle of plant destruction, the scientists added.
The Cornell scientists began their discovery process by selecting wild tomatoes (Lycopersicon pnennellii, the relative of a commonly cultivated tomato, L. esculentum) with few insect blemishes, then washing the fruit to obtain the natural compounds for chemical analysis. The exact mixture of glucose esters and other compounds would have been too complicated to duplicate, Ganem said, so they narrowed their formulation to some simple analogs with common structural and physical properties.
"Now the chemistry is easy," Ganem said, noting that the patent covers several similar formulations of the pest repellent. The "non-cyclic" term means each compound's carbon atoms are arranged in chains, rather than in rings.
Mutschler and Ganem hope to take their invention to the next stage -- a marketable product with all the emulsifiers and stabilizers that are expected by consumers -- through a Technology Development Fund Grant from Cornell's Office of Economic Development.
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