Natural Product Helps Insects “Bite the Dust”

By Linda McGraw
December 22, 1999

Remnants from one of the oldest things on earth--diatomaceous earth (DE)--can help solve one of today’s most pressing problems: finding safe alternatives to insecticides to control insects in homes and food processing facilities, according to Agricultural Research Service scientists.

DE is dust made from the fossilized skeletons of microscopic aquatic plants. ARS researchers are testing new commercial DE products in laboratory studies. DE is non-toxic to humans, but it kills red flour beetles and confused flour beetles, two of the food processing industry’s worst insect pests. DE disrupts the insects’ exoskeleton or skin, causing the insects to die from rapid water loss.

According to ARS entomologist Frank H. Arthur, DE could be an alternative to methyl bromide, an ozone-depleting fumigant scheduled to be phased out by 2005.

Fluctuations in temperature and relative humidity can affect the performance of DE products used to control insects. Adult insects were exposed to DE at various temperatures (70, 80, and 90 degrees F) and relative humidities (40, 57, and 75 percent). Exposure to DE at 80 degrees F. and 57 percent relative humidity for two days killed all red flour beetles, but three days were required to kill 100 percent of the confused flour beetles. DE kills insects quicker at higher temperatures and at lower humidities.

Arthur is based at ARS’ Grain Marketing and Production Research Center in Manhattan, Kan. His research also focuses on alternatives to insecticides used in raw grain storage. While DE is a good alternative to chemical insecticides, Arthur stresses the importance of combining a product like this with good sanitation.

ARS is the chief research agency for the USDA.

Scientific contact: Frank H. Arthur, ARS Grain Marketing and Production Research Center, Manhattan, Kan., phone (785) 776-2783, fax (785) 776-2792, arthur@usgmrl.ksu.edu.