Insecticide Netting Could Keep Beetles Out of Your Breakfast Cereal
By Meredith Swett Walker
Most of us take it for granted that we can eat our morning bowl of granola without inspecting every spoonful for bits of flour beetle or grain borer grubs. That nonchalance is pretty astounding when you consider the long journey that foods like wheat, corn, and soybeans make from field to dining table and the dozens of species of insects that are eager to snack on them along the way.
Having a pantry stocked with insect-free food is only possible because of sustained integrated pest management efforts that begin when food is harvested and don’t end until we eat it.
Controlling pests in our stored food is a big deal. “Stored commodities”—things like wheat, corn, and soybeans, as opposed to fresh produce—are not only necessary to feed human populations but also worth a lot of money. In the United States, the value of the 2017 corn crop alone was about $47.5 billion dollars. But damage due to insect pests causes an estimated 10-30 percent loss in value for these commodities. In developing nations, with fewer pest management resources, the losses can be up to 70 percent.
Pest managers in stored commodities facilities need effective and safe tools. In a study published this month in the Journal of Economic Entomology, Rob Morrison, Ph.D., and colleagues at the U.S. Department of Agriculture-Agricultural Research Service’s Center for Grain and Animal Health Research and Kansas State University examine the effectiveness of long-lasting insecticide netting in controlling two major stored commodities insect pests.
Long lasting insect netting (LLIN) is netting that has insecticide incorporated into its fibers and can be effective for a year or more. It has long been used as mosquito netting to protect people against malaria and other diseases, but entomologists have only recently begun looking at using LLINs for other purposes. For instance, in 2017 researchers at Virginia Tech examined how LLIN might aid in control of the brown marmorated stink bug (Halyomorpha halys), an invasive urban and agricultural pest.
Currently, facilities that store grain and other commodities primarily control insect pests via careful sanitation (spilled grain can provide places for pests to breed) and fumigation if pests are detected. But many pest species are developing resistance to the fumigant (phosphine), and many consumers prefer food with minimal exposure to pesticides.
To determine if LLIN could be an alternative or complementary pest control tool, Morrison and colleagues conducted experiments with two major stored product pests, the red flour beetle (Tribolium castaneum), and the lesser grain borer (Rhyzopertha dominica). The researchers evaluated both lethal and sublethal effects on the beetles, because sublethal effects, like reduced locomotion, can reduce a pest’s dispersal ability—another goal of pest management. In a series of experiments, adult beetles were exposed to LLIN (with 0.4 percent deltamethrin) or control netting (no insecticide) for short periods of time (1-, 5- or 10-minute intervals), and the beetles’ movement, mortality, and dispersal were measured.
Their results suggest that LLIN could indeed be useful for pest control at stored product facilities. Beetles exposed to LLIN moved significantly shorter distances and had more erratic movements than did beetles exposed to control netting. Exposure to LLIN also significantly reduced both species ability to disperse to new food sources. These sublethal effects suggest that LLIN could help reduce spread of the beetles, even if contact with the netting does not kill them all of them. Finally, exposure to LLIN did significantly increase mortality in both beetle species, especially the lesser grain borer, in which only 3.7 percent of adult beetles survived exposure to LLIN.
Morrison says one advantage of LLIN is that it need not be in contact with the food products. “I believe these LLINs could successfully help prevent the movement of insects into a food facility by using them to seal vents, awnings, openings, and windows around a facility,” he says. In addition, LLINs could be a component of an “attract and kill” device like those used on brown marmorated stink bugs, says Morrison. These devices lure pests in using pheromones or food and then kill them, for instance with LLIN.
Pests—and the entomologists working to control them—are everywhere. “Whether folks are aware or not, pest management occurs at big box stores to protect finished products before they are bought—it occurs on container ships, warehouses, trains, semi trucks, retailers, and maybe even right in your own kitchen,” says Morrison. Without effective pest management tools, which may soon include LLIN, our food would be a lot less appetizing and we’d have a lot less of it.
Journal of Economic Entomology
Meredith Swett Walker is a former avian endocrinologist and wannabe entomologist. She now studies the development and behavior of two juvenile humans in the high desert of western Colorado. When she is not handling her research subjects, she writes about science and nature. Find a sampling of her work at www.magpiescicomm.com.