Originally Published In The Deseret News -- Wednesday, January 6, 1993
Fumigating With Dry Ice, Cautious Use Of Sprays Add Life To Grains And Groceries.
This week's column covers an unmentionable subject, or at least one never mentioned in polite company. Insects in your food are unappetizing and unappealing but occur frequently because our lifestyle encourages them. Estimates show Utah families have over $50 million worth of food stored in addition to that stored in warehouses and grocery stores. Stored food becomes a breeding ground for insects unless special steps are taken to keep them out.
The first step is always prevention. Buy clean, insect-free grain products with a moisture content of 10-12 percent from a reputable source. Store food in metal or food-grade plastic cans with tight-fitting lids. If cans do not seal tightly, use duct tape to prevent insects from entering. A five-gallon can stores approximately 35 pounds of wheat. Store the containers in clean, cool, dry places, off of the floor and away from damp areas. Do not store any products in open containers, paper or burlap sacks. Most plastic bags are also not insect proof. Rotate the food so that older stock is consumed first.
Cleanliness is important when controlling insects. For long-term storage, buy commercially treated grain products or fumigate with dry ice. Dry ice is not the most effective fumigant for controlling pests, but it is safe to use in the home. Fumigate home-stored grains by putting 2 ounces of crushed dry ice (about the size of a golf ball) on three or four inches of grain in the bottom of a five-gallon container, then add the remaining grain. When fumigating larger quantities, use one pound of dry ice per 100 pounds of grain. Dry ice gives off carbon dioxide, a gas that displaces oxygen in the cans. Carbon dioxide is trapped in the container and insects will not survive. This treatment destroys larvae and adults, but may not destroy eggs and pupae. Fortunately, the lack of oxygen should keep those pests from developing if the container is not opened after storage. Containers should not be sealed until the ice has been allowed to sit for approximately 30 minutes. Small quantities of grain (one to 10 pounds) can be put in heavy plastic bags and placed in a freezer for a week to kill any living insects.
There are many different insects that feed on stored products. Grain beetles, weevils, moth larvae and other insects all contaminate home-stored grains. In Utah, this amounts to an estimated annual loss of $1 million. Homeowners usually notice small black or brown beetles or their larvae in the food or small moths or worms crawling on walls.
If you discover any signs of insects, locate the contaminated food and decide whether it should be discarded or salvaged. Most food should not be saved if it is badly infested with insects. If you desire to save infested foods, use the fumigation method or freezing method described previously. Clean up any spilled food and place the food in an insect-proof container. Sprays may be needed to control pests in severe cases.
Locating the contaminated foods is often the hardest part of a control program. One major source of food for pests is crumbs in and around cracks of kitchen cupboards or in carpets and other areas where food is consumed. Clean and vacuum storage areas, including cracks and backs of shelves. Wash with a good detergent or disinfectant.
Spraying is not highly effective against these pests unless used with a good sanitation and prevention program. Crack and crevice sprays of household aerosol or pump insecticides containing pyrethrins, .5 percent diazinon, .5 percent Dursban (cholorpyrifos), .5 percent Baygon (propoxur) or Malathion may be used. Do not contaminate food, food stuffs or dishes. Read and follow all pesticide label directions and do not apply any materials to sites that are not listed on the labels. Apply only to the cracks and crevices and do not treat the entire area. Allow sprays to dry before replacing food. If your cupboards have shelf liners, discard and replace them. If insects persist, it means that food sources still remain and the process will have to be repeated until all infestations are eliminated.
Total-release aerosols or insect foggers can also be used in some locations. Most of these require leaving your home for a period of time after releasing the aerosol. They are only effective against larvae and adults, so will need to be repeated weekly for one- to two-week intervals for at least three successive treatments.
Bay leaves, chewing gum, iron nails, diatomaceous earth, ultrasonic pest repellers and other products have often been sold as insect preventers. Unfortunately, none of these have been shown by research to prevent insects from infesting your food. While stored-food pests may not cause serious economic damage, they are a great nuisance and are unappealing aesthetically. Select and store food carefully and prevent insect infestations to enjoy a safe, clean and appetizing food supply.
Larry A. Sagers is a horticulturist with the Utah State University Extension Service.
© 1998 Deseret News Publishing Co.