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Silicon dioxide (diatomaceous earth)

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Silicon dioxide may be used to control earwigs
Photo: René Limoges

Caution
The information below is intended only as a guide. Always read product labels carefully.

Product description

Silicon dioxide (diatomaceous earth) is a powder consisting of many tiny abrasive crystals, obtained by grinding up the fossilized remains of diatoms, microscopic algae.

Pesticides with silicon dioxide as the active ingredient are used as insecticides and molluscicides. Manufacturers or users may add bait, like powdered sugar, to attract target pests.

Target pests 

Pesticides with silicon dioxide as the active ingredient may be used to control a variety of pests, including:

NB: The product label lists the plants on which the pesticide may be used, along with the target organisms. 

How it works

Silicon dioxide causes small abrasions on the body of any pest that comes into contact with the powder. The pest gradually loses its body fluids, dehydrates and dies.

When bait is added, pests tend to eat the product. The crystals then abrade their digestive systems and kill them.

It may take a few days to eliminate pests after the pesticide is applied.

Application

The product should be applied to pests or to spots that they frequent. It may be sprinkled directly on the leaves of affected plants, avoiding flowers so as not to harm pollinating insects. It may also be applied to the soil (without working it in) around the base of plants to be protected.

It is best to apply it during dry weather, because silicon dioxide loses its effectiveness when wet.

Precautions

The product may irritate the respiratory tract if inhaled, so it is best to wear a mask when applying it. In addition, because it may irritate the eyes, it is best to wear goggles. It should be applied on calm days, to keep it from drifting.

Pesticides with silicon dioxide as the active ingredient are not selective and may harm beneficial garden organisms such as earthworms. This means that they should be used only as a last resort and for spot treatment only.

Do not use near any body of water or wetland, or dump any pesticide or rinse your equipment there, as this will contaminate the water. Never dump pesticides down sewers.

Keep out of reach of children. 

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