Diatomaceous Earth (DE) is a naturally occurring, soft, silica-based sedimentary rock that crumbles into a fine powder. This powder is composed of the fossilized remains of diatoms, which are microscopic, single-celled aquatic organisms. When used in the lawn and garden, DE acts as a mechanical insecticide, controlling pests like ants, fleas, and mites by causing desiccation. The fine, sharp edges of the silica particles scratch the insect’s protective outer layer, leading to moisture loss and eventual dehydration.
Selecting the Proper DE and Safety Gear
The product you choose must be Food Grade diatomaceous earth, which is composed primarily of amorphous silica. This type is untreated and contains less than 1% crystalline silica, making it suitable for pest control around homes and gardens. You must avoid using Filter Grade or Pool Grade DE, as this material has been heat-treated, a process called calcination, which significantly increases its crystalline silica content. Crystalline silica is a respiratory hazard and should only be used for industrial filtration, not for pest control applications.
While Food Grade DE is not poisonous, the fine powder can irritate the eyes, skin, and respiratory system if inhaled. Wearing a dust mask or respirator is necessary to protect your lungs from the microscopic silica particles. You should also wear protective eyewear and garden gloves to prevent eye irritation and excessive skin drying.
Step-by-Step Dry Application Methods
The effectiveness of DE depends entirely on it remaining dry, so you must select a day with no wind and no rain forecasted for at least 24 to 48 hours. For optimal results, the lawn itself should be dry before you begin the application process. Mowing the grass to a slightly shorter height beforehand will help the DE reach the soil surface, where many lawn pests reside.
For applying the powder to large areas, a broadcast spreader can be used, though you must first adjust the setting to ensure a light, even distribution. For smaller or more targeted areas, a handheld duster or a specialized crank duster works well to puff the powder directly onto the grass. Alternatively, a flour sifter or fine-mesh shaker can provide an adequate light coating for spot treatments.
The goal is to apply a very fine, nearly invisible layer of powder across the affected area. Thick piles of DE can actually deter pests from crossing the barrier, reducing the treatment’s impact. Focus the application low to the ground to ensure the DE reaches the base of the turf and the top layer of the soil. This placement is crucial because it targets crawling insects as they travel across the surface.
Maintaining Effectiveness and Reapplication Schedule
Because DE works by physical contact and desiccation, it must remain a fine powder to be fully effective. Any moisture, such as rain, heavy dew, or irrigation, will cause the powder to clump and lose its sharp, abrasive properties. Although the DE will regain some of its efficacy once it dries out completely, the original distribution may be compromised.
For this reason, reapplication is necessary anytime the treated area becomes substantially wet. If there is heavy rainfall or you use a sprinkler system, you should reapply the powder once the lawn has dried. In the absence of precipitation, a general reapplication every one to two weeks is often recommended until the pest issue is under control.
After applying the DE, you should avoid watering the lawn for at least 24 to 48 hours to allow the powder to settle and begin working. Maintaining this dry period maximizes the contact time between the pests and the silica particles.