The porous property of Diatomaceous Earth has earned a perfect spot in many industrial applications. Its suitable use as filter purifies wines, beer, fruit juices, pharmaceutical products, solvents, food additives, etc. Besides this, DE is highly effective as a vanguard for pests. Ancient civilizations already exploit the benefits of this mineral. Ancient China had been using DE 4000 years ago. The Aztecs in Mexico have been protecting their grains from pests using the same mineral. Insects slowly die when they brush with the DE material as its extremely dry property absorbs the waxy layer of insect cuticle, which result to extreme dehydration of the insect.
Diatomaceous Earth is almost harmless to mammals. It is safe to mix with food. This siliceous mineral in a fine powder form is commercially available worldwide to be used as stored grain protectant. Countries like USA, Canada, Germany, UAE, Saudi Arabia, Australia, Brazil, China, Japan, Indonesia, Philippines, and many more have all been commercially distributing DE products to kill or deter pests that attack grains.
Insects vary on how long they can last to DE, but the most vulnerable are insects with flat bodies, with body hair, thin cuticle, low-melting bodily grease, and those thriving on dry grain. Insects that are most vulnerable belong to the genus Cryptolestes (Flat grain beetles). Less vulnerable are the Sitophilus spp. (i.e. Rice Weevil, S. Oryzae), then by genus Oryzaephilus (i.e. Sawtoothed grain beetle, O. Surinamensis). Going further to the lesser sensitive insect are the Rhyzopertha (i.e. Lesser Grain Borer, R. Dominica). The most tolerant belong to Tribolium spp. (T. Confusum, the confused flour beetle).
Some places in Africa, traditional farmers mix sand or ash on stored grains to ward off insects attracted to grains. The principle behind is to use the abrasive properties of the sand/ash material to brush against the cuticle of insects as they crawl on sand or ash-filled grains. In the same sense, DE dust is mixed with stored grains to ward off insects. But there are factors to consider that will influence effectiveness. One is climate condition and the other is the cohesion of DE material to the commodity. Reports showed that DE did not stick as much to maize product as did to wheat or sorghum.
In Tanzania, Africa, the most destructive insect that swarm on stored grains is Larger grain borer (Prostephanus truncates). It is responsible for 40 percent of grain losses. This insect is not endemic in the said region, but is believed to have originated in Central America arriving in Africa in food shipments during 1980s. This insect has spread to East, West, and Southern Africa.
Application of DE on Stored Grains
Diatomaceous Earth is best applied and recommended on newly harvested, dry, and non-infested grains. Winnowing should precede prior to DE mixture with the grains. Ideal condition for best DE protection is a low relative humidity of 50 percent rh. Relative humidity influences how fast insects losses bodily fluid.
Choose a storage place away from winds with smooth and even floor. Clean the floor from any existing debris. Mixing of Diatomaceous Earth with the grains may be done on the clean floor. Make certain that you wear a mask to protect yourself from inhaling the dangerous DE dust. Be sure that proper or suitable mask is used to serve as long-term protection when regularly applying DE dust on stored commodities.
- Put 50 kg of grain on the cleared floor.
- Sprinkle the correct amount of DE (refer to product specification) on the heap of grain on the floor.
- Using a clean shovel, slowly scoop the grains upward covering the applied DE.
- Gently mix together the grain and DE dust by shovelling onto one side to form a new mound of mixed grain and DE. This is the 1st mixing.
- Shovel again the new mound of grain. This is the 2nd mixing.
- Shovel back again onto one side. This is the 3rd mixing.
- Place the treated grains inside a bag, then sewn up ready for storage.
- The treated grains can now be piled inside the storage facility.
There are many advantages of using DE in treating stored grains. The major advantage is that it is non-aggressive to health and environment. The extremely low toxicity of DE is categorized by the EPA as “Generally Regarded as Safe.” When mixed at 0.1% w/w, DE is effective on most insects. DE is also easily removed during processing, about 98%. Diatomaceous Earth has the tendency to reduce the flow effect of grains. Therefore, it is applied only to the top and bottom layers of the stored grains.