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Synthetics Mimic Natural Brain Chemicals

Changing an insect's behavior by "messing with its brain" may be the way to stop pests in the future. Agricultural Research Service scientists have developed artificial brain chemicals designed to mimic natural chemical messengers that control molting and other life functions.

"Commercial products containing artificial neuropeptides that can be sprayed onto corn earworms, for example, could be developed in about 5 years," says Ronald J. Nachman. He is a chemist in the ARS Veterinary Entomology Research Unit at College Station, Texas.

Nachman and ARS entomologist G. Mark Holman began studying neuropeptides--chemical messengers sent out in insect brains to stimulate life-sustaining functions--in 1987. These messengers are made up of strings of amino acids, the building blocks of protein, and control an array of behaviors. They can halt molting (shedding of outer covering), upset mating, alter digestion, or disturb water balance.

By 1996, Nachman and Holman had built the first of eight analogs--artificial versions that mimic natural brain chemicals.

The artificial versions don't work quite like the real thing.

The biggest problem in delivering the mimics was getting them to penetrate the pest insects' tough skin, or cuticle. Nachman overcame this obstacle in the laboratory by using a combination of boron, carbon, and other chemicals, replacing one part of a string of amino acids with this combination. The result: The molecule became greasy. The greasy quality of the molecule matched the physical characteristic of the insects' cuticle, making absorption into the insect possible.

Nachman sent his greasy analog to ARS insect physiologist Peter E. A. Teal in Gainesville, Florida, for further testing.

To stimulate the production of sex pheromones, Teal applied the analog to the skin of tobacco budworms and cotton bollworms. Both of these major cotton pests have adapted to commonly used chemical insecticides, making them less effective, notes Teal.

Normally, these insects produce pheromones--in this case, female sex odors released to attract males for mating--for 3 hours. Teal demonstrated that some of the analogs caused both species to produce pheromones nonstop for 20 hours.

"This strategy could cause the insect to run out of pheromone-producing chemicals and make it impossible for the insect to attract mates," says Teal.

This work represents a significant milestone in developing environmentally friendly pest insect management strategies. Nachman, Teal, and Holman are pursuing patents on all the compounds.--By Linda Cooke McGraw, Agricultural Research Service Information Staff, 1815 North University Street, Peoria, IL 61604, phone (309) 681-6530.

Ronald J. Nachman and G. Mark Holman are in the USDA-ARS Veterinary Entomology Research Unit, 2881 F&B Rd., College Station, TX 77845; phone (409) 260-9315, fax (409) 260-9377.

Peter E. A. Teal is in the USDA-ARS Chemistry Research Unit,Center for Medical, Agricultural, and Veterinary Entomology, 1700 SW 23rd Dr., Gainesville, FL 32604; phone (352) 374-5788, fax (352) 374-5707, e-mail

"Synthetics Mimic Natural Brain Chemicals " was published in the May 1998 issue of Agricultural Research magazine. Click here to see this issue's table of contents.