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Near- Infrared Means “Lights Out” for Stored-Grain Insects

By Linda McGraw
December 15, 1997

Scanning individual wheat kernels with the energy of near-infrared (NIR) light waves--a zone of the spectrum invisible to the human eye--can reveal hidden insect infestations that lower wheat quality. NIR can also identify and kill the pests, according to scientists reporting findings today in Nashville, Tenn.

In studies last June, exposing wheat kernels to NIR killed 100 percent of the rice weevil larvae infesting them. Scientists with the Agricultural Research Service ran the tests. The ARS scientists are the first to combine NIR with an automated grain handling system to rapidly detect hidden insects in wheat kernels. They envision using the technology with grain samples or with grain on conveyor belts at storage and food-processing facilities.

Damage from larvae of the lesser grain borer, rice weevil and maize weevil costs the U.S. wheat industry about $500 million annually. Detecting the infestations has been a serious problem. Grain storage operators can save on fumigation costs if they know which pest is the main culprit in their grain bins. But while a rice weevil looks like a granary weevil, NIR technology quickly reveals which is which.

Each insect species has a unique light signature based on its body content of carbon, hydrogen and nitrogen. This body chemistry determines how much light is absorbed. In response, the NIR instrument produces a graph--much like a cardiogram--with the telltale peaks and valleys unique to a particular insect species.

The NIR instrument includes two pieces of equipment known as a diode array spectrometer and a wheat singulator. The instrument was developed by Perten Instruments, Springfield, Ill., and engineers at ARS’ Grain Marketing and Production Research Center, Manhattan, Kan.

Today, entomologist James E. Throne reports on the NIR studies in Nashville at the annual meeting of the Entomological Society of America. Throne works at ARS’ Manhattan center.

Scientific contact: James E. Throne, ARS Grain Marketing and Production Research Center, Manhattan, Kan, phone (785) 776-2796, fax (785) 776-2792,