Diatomaceous earth (DE) is often suggested as a natural method for managing pests, including chiggers, which are tiny, irritating mites. DE can be an effective control method when applied correctly to the environment where these pests live. Its success is due to the physical way the powder interacts with the chigger’s microscopic body structure. This article explores the nature of chiggers, the science behind DE’s action on pests, and the practical steps for using it safely to reclaim outdoor spaces.
Identifying Chiggers and Their Behavior
Chiggers, also known as harvest mites or red bugs, are not insects but are the larvae of mites in the family Trombiculidae, making them tiny arachnids. The life stage that affects humans and pets is the six-legged larva, which is extremely small, typically measuring only 1/120 to 1/150 of an inch, making them nearly invisible to the naked eye. These parasitic larvae hatch from eggs laid in damp soil during warm weather. They climb onto vegetation like tall grass, weeds, or brush, waiting for a host to pass by.
Contrary to common belief, chiggers do not burrow into the skin or suck blood. Once attached, they use blade-like mouthparts to cut the skin and inject a digestive enzyme. This enzyme breaks down skin cells, which the chigger then consumes as a liquid, often remaining attached for several hours or days. The intense itching and red welts are a reaction to the injected enzyme and the hardened skin cells, which form a feeding tube called a stylostome.
Chiggers prefer areas where clothing fits tightly, such as around the ankles, waist, or behind the knees. They are most active from early spring through late fall when ground temperatures are warm. The adult and nymph stages do not feed on humans; instead, they are beneficial predators of small soil-dwelling insects. Understanding this larval behavior and habitat preference—low on vegetation in brushy, grassy, or overgrown areas—is important for effective treatment.
How Diatomaceous Earth Works on Pests
Diatomaceous Earth (DE) is a natural, fine powder made from the fossilized remains of diatoms, which are microscopic, single-celled aquatic organisms. These fossils are composed primarily of silica. When crushed, their skeletons yield a powder with microscopic, razor-sharp edges, which is the source of its effectiveness against pests like chiggers.
The mechanism of action is mechanical, not chemical, which prevents pests from developing resistance. When a chigger or other small arthropod crawls across the powder, the sharp particles scratch and cut through the protective waxy outer layer of its cuticle. This damage allows the chigger’s vital body fluids to escape, while the highly absorbent silica simultaneously absorbs the oils and moisture from its body.
This dual action leads to rapid desiccation of the pest. Use only Food Grade Diatomaceous Earth for pest control, as this form is purified and safe for use around humans and animals. Filter Grade DE is heat-treated, contains a different type of silica, and is unsafe for general pest control applications.
Practical Application and Safety Measures for Chigger Treatment
To use Diatomaceous Earth for chigger control, apply it directly to areas where the larvae are active, focusing on hot spots like the yard perimeter, tall grass, and garden borders. Since the powder works by physical contact, a thin, even layer is sufficient to cover the ground and low vegetation. Application should occur when the area is dry, as moisture can cause the fine powder to clump, which temporarily reduces its abrasive and desiccating effectiveness.
Application Methods
For broad outdoor coverage, DE can be applied using a hand duster or a broadcast spreader. It can also be mixed with water to create a slurry. A common mixture is approximately four tablespoons of DE per gallon of water, which can be sprayed onto hard-to-reach areas. Once the water evaporates, the fine DE powder remains as a residue on the surface, ready to contact the chiggers. Reapplication is necessary after heavy rain or irrigation.
Safety Precautions
The primary safety measure when applying DE is to avoid inhaling the fine dust, which can irritate the respiratory system, especially for those with existing conditions. Wearing a dust mask or respirator, along with protective goggles and gloves, is recommended during application. While Food Grade DE is considered non-toxic and generally safe for children and pets once the dust has settled, keep them out of the treated area until the powder settles onto the surface. DE is an environmental control and is not meant to be used on the skin to treat existing chigger bites.