Treating Dried Foods For Insects
The single most effective recommendation for long-term wheat storage is to start with clean, pest-free wheat placed in clean containers.
Dry Ice (recommended)
Dry ice is frozen CO2. Treatment with dry ice may improve storage life of the grain, but it is not the most effective fumigant for controlling pests in stored grain. A single treatment with dry ice is sufficient for long-term storage. Annual dry ice treatments are not necessary unless an infestation is recognized in the stored grain.
Oxygen absorbers or vacuum sealing (recommended)
Insects require oxygen to survive, so removing that oxygen is an effective insect prevention measure. The nature of the equipment and plastic or mylar bags makes this practical for only smaller quantities of grains (1-2 lbs) per bag. Oxygen absorbers will work to kill pests in 5 gallon plastic buckets, but these buckets will slowly allow oxygen back inside. (Personal communication LDS Food Storage Research)
To control insects by freezing, 1-15 pounds of grain should be placed in a medium to heavy plastic bag or double bagged and stored in a freezer for 2-3 days. Eggs of insect pests, if present, will not be affected by freezing. Warm grain for 24 hours to allow some eggs to hatch. Repeat freezing cycle. Multiple freeze-thaw cycles may be required.
Diatomaceous Earth (DE) (not recommended)
The use of diatomaceous earth (DE) as an insecticide is a "commercial" alternative to traditional chemical insecticides. DE is of natural origin, leaves minimal residues on the product and has low mammalian toxicity. DE “inactivates” the waterproof lipids of insects’ causing them to die through desiccation. While overall, DE’s work well as an insecticide, specific DE formulations must be tested for activity in each product and against each insect species. In addition, while DE is not a chemical hazard it is an inhalation hazard. Thus, the nature of the silica powder in DE determines the risk. This makes home insecticidal use impractical and potentially harmful. (See references 1 & 2).
Bay leaves, chewing gum (mint flavored or otherwise), 10-penny nails, or salt (not recommended)
These treatments are considered old wives tales and there is no research-based evidence that they work.Scientific References:
- C.G. Athanassioua, N.G. Kavallieratosb and C.M. Meletsisc. Insecticidal effect of three diatomaceous earth formulations, applied alone or in combination, against three stored-product beetle species on wheat and maize. Journal of Stored Products Research. Volume 43, Issue 4, 2007, Pages 330-334.
- Subramanyam, Bh. and R. Roesli. 2000. Inert dusts, pp. 321 - 380. In Subramanyam, Bh. and D. W. Hagstrum. (eds.), Alternatives to pesticides in stored-product IPM. Kluwer Academic Publishers, Boston, Massachusetts.