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Insecticide Netting Could Keep Beetles Out of Your Breakfast Cereal

red flour beetle on long-lasting insecticide netting

In this close-up view, a red flour beetle (Tribolium castaneum) lies dead in long-lasting insecticide netting. A new study shows that such netting could have promising applications in stored-product facilities to protect foods like wheat, corn, and soybeans from pests. (Photo credit: Rob Morrison, Ph.D.)

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.

Meredith Swett Walker

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.

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.

8 Comments »

  1. For decades we’ve been hearing about “new less toxic” stored product beetle and moth pest control technologies, e.g. insect growth regulators, pheromones, diatomaceous earth, etc., but they havn’t widely embraced by the food processing and warehousing industries because they havn’t been acceptably effective in real world settings.

    • Yes, and mating disruption has proved so effective now for indianmeal moth that it has been adopted by over 1,500 store locations of a big box retailer. Pheromone-based monitoring traps are regularly used by the industry, and other tactics have been incorporated besides just fumigating with methyl bromide (now banned in the US) or phosphine. If that is not progress, then I don’t know what is. I’ve only been working in stored products for less than two years, so I can’t really vouch for prior endeavors, but give me time, and I am sure you’re going to see even more good things come. You don’t know if something is going to work unless you put in the effort and do the research and try to take it to stakeholders. Cynicism won’t get anyone far in any research field.

  2. Ah yes, we had red flour beetles infest our larder once. Just made sure to sieve our flour and mom used to joke how if we ate a few it would be a good source of protein! But I can see how they’d be a terrible problem commercially and it’s good to see new ways of combatting them.

  3. I am disturbed by this netting situation, because it sounds indiscriminate; bees and other beneficials would get caught by it as well. What is being done, do you know, in the area of avoidance controls for insects rather than new ways of killing them? After all, the issue is to keep them out of certain areas, which seems like it could be done more economically, more specifically and less destructively utilizing biological controls. I’d like to know what is happening along those lines. Paul C. there has a good point.

    • Pollinators have no interest in stored grain silos or facilities, which is the only place that this net would be used. You most often find pollinators on or near flowers, and since areas around food facilities or mowed or otherwise well-manicured, it is highly improbable a pollinator will ever contact this netting. The use of nets is far less indiscriminate than fumigating a whole food facility. Using long-lasting insecticide nets focuses use of insecticide to the net and away from the commodity, which is what people are going to be consuming. Given the choice between reduced chemical input or chemical free commodities/foodstuffs plus insecticide nets compared to the use of fumigants with high mammalian toxicities, dangers to workers, and environmental hazards, I’d probably choose the former.

      In terms of biological controls, I agree that its always best to rely on natural enemies for long-term suppression of pests. But, the US has strict regulations on the number of insect fragments per weight of a specific commodity. Having natural enemies get into grain contributes to this limit, and could result in the rejection of miller’s and other processor’s products. So, unfortunately, in a system with such low tolerances for insects, this doesn’t seem to be a viable option. However, we are researching methods of manipulating the behavior of pest populations using pheromones, food cues, and repellents in my lab with the long-term goal being behaviorally-based management that will result in further reductions in fumigant and chemical use.

  4. Insect pests of stored grains can be a source of protein. Entomophagy is a vital altenate source of protein in developing Nations and is currently being promoted in Developed Nations. Yes, we MUST reduce the anount of grains we lose through insect pest damage. The level of acceptable yeild reduction MUST be examined from a cultura, sociological and nutrition point of view.

    • I agree with your points. Some of the other research in the unit at my facility involves looking at rearing insects as a source of protein for various products. There is nothing inherently wrong with eating insects, and it may even be a source of sustainable protein, but this is something that the US must reckon with as a society, and if people feel strongly about it, there should be concerted to change the rules. However, regardless, insects are our main competitors for food on the planet, and the post-harvest food supply chain presents an enormously tasty opportunity to hundreds of species of insects who would love to get their little tarsi on our food before we can use it. Given the rapidly growing world population, the constraints of global climate change, and diminishing energy reserves, I am in favor of using any tool that helps us meets the goal of living in a more sustainable society, whether that includes entomophagy or innovative solutions to our most pressing pest problems.

      • I am glad to hear that your lab also promotes entomophagy. I am of the opinion that the latter source of food (protein) will dominate human source of protein in the future. IT TAKES LESS FOLIAGE AND ENERGY TO PRODUCE THE SAME AMOUNT OF PROTEIN , COMPARED TO CURRENT MEAT AND BEAN PRODUCTION METHODS.

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