University of Arkansas Division of Agriculture scientists are studying methods of eliminating insect pests from stored rice without using pesticides.

Dr. Terry Siebenmorgen, professor of food science, and Derek Schluterman, a recent graduate in biological engineering, worked with Dr. Frank Arthur of the USDA Agricultural Research Service in Manhattan, Kan., to investigate a means of killing insects in rice by heating it with infrared energy.

“The rice industry has requested that we look at ways of controlling insects without using chemical pesticides,” Siebenmorgen said. “It’s also likely that consumers will increasingly demand foods on which no pesticides are used.”

Arthur, an entomologist, said insects such as rice weevils, lesser grain borers and Angumois grain moths are of particular concern to rice producers and processors because they feed from the inside of rice kernels. Rice weevils were used in the tests.

Biological engineering student Derek Schluterman places rice samples in an infrared unit for a research project to see if infrared treatment is an effective means of reducing insect pests in stored rough rice.

Infrared energy heats the rice to a temperature the insects cannot survive, Siebenmorgen said. Using an infrared rice drying unit provided by Catalytic Drying Technologies of Manhattan, Kan., and funding from the Arkansas Rice Research and Promotion Board, Siebenmorgen, Schluterman and Arthur set out to determine the minimum temperature necessary to kill the insects and the necessary infrared intensity and exposure duration to achieve those temperatures within the rice kernels.
 
Schluterman sent rice samples to Arthur, who infested them with rice weevils. Schluterman then treated the samples with infrared to temperatures of 50 degrees, 60 degrees and 70 degrees Celsius (122 degrees, 140 degrees and 158 degrees Fahrenheit).

To determine the effectiveness of the IR treatments in killing the insects at various life stages, Schluterman incubated the treated samples for six to seven weeks to see if insects would hatch out of the rice. Some samples were incubated without infrared treatment as a control.

“We killed most of the insects at 60 degrees,” he said. “We got them all at 70 degrees.”

Dr. Jean-Francois Meullenet, UA food scientist, said the infrared treatment has little affect on food quality or sensory characterstics.

“Infrared treatment can be an effective alternative pest control method for organic rice industries and can also reduce the number and cost of pesticide treatments,” Arthur said.