Can You Use Diatomaceous Earth Outside? A Comprehensive Guide
Yes, diatomaceous earth (DE) can be used outside, and in many cases, it’s highly effective. However, its effectiveness and longevity are significantly affected by environmental factors, particularly moisture. Understanding the type of DE and proper application methods are crucial for successful outdoor use.
Understanding Diatomaceous Earth
What is Diatomaceous Earth?
Diatomaceous earth is a naturally occurring, sedimentary rock composed of the fossilized remains of diatoms, a type of hard-shelled algae. Mined from ancient lakebeds and marine deposits, DE is widely used for its insecticidal, absorbent, and filtering properties. The sharp edges of the diatom skeletons are what make it effective against insects. There are two main types: food-grade diatomaceous earth and filter-grade diatomaceous earth. Only food-grade DE is safe for use around humans, pets, and food sources. Filter-grade DE is primarily used in industrial applications, such as swimming pool filters, and should never be ingested or inhaled.
How Does Diatomaceous Earth Work?
DE works primarily through desiccation. The microscopic, sharp edges of the diatom skeletons abrade the waxy outer coating (cuticle) of insects, causing them to lose moisture and eventually dehydrate. This makes it a potent, yet non-toxic (in food-grade form), insecticide. It’s also effective as an absorbent material, soaking up liquids and oils.
Types of Diatomaceous Earth
As mentioned, the two primary types of DE are food-grade and filter-grade. Food-grade DE has been processed to be safe for consumption by animals and humans (though ingestion is typically for specific purposes like parasite control in animals). Filter-grade DE is calcined (heat-treated) to alter its structure, making it a better filter. This process also makes it significantly more hazardous to inhale. Always use food-grade DE for any application where human or animal exposure is possible.
Outdoor Applications of Diatomaceous Earth
DE can be a valuable tool in outdoor pest control and soil amendment, but its limitations must be considered.
Pest Control
Diatomaceous earth is effective against a range of outdoor pests, including ants, aphids, slugs, snails, and certain types of caterpillars. It works best when applied directly to the insects or to areas where they are likely to travel. It’s particularly effective in drier climates or during periods of low humidity.
Garden Use
DE can be used in gardens as a soil amendment, improving drainage and aeration. It also helps to retain moisture in sandy soils. Additionally, its insecticidal properties help to protect plants from pest infestations. Sprinkle it around the base of plants, avoiding the foliage as much as possible, to create a barrier against crawling insects.
Livestock Areas
DE can be used in livestock areas to control flies and other insect pests. It can be sprinkled in bedding, around feeders, and in areas where animals congregate. It’s also sometimes added to animal feed as a natural dewormer (consult with a veterinarian before doing so).
Challenges and Considerations for Outdoor Use
While DE offers several benefits, its effectiveness outdoors is contingent on several factors.
Impact of Moisture
Moisture is the biggest enemy of DE’s effectiveness. When wet, the diatom skeletons clump together, losing their ability to abrade insects. Rain, dew, and even high humidity can render DE temporarily ineffective. Reapplication is often necessary after rain or heavy dew.
Application Techniques
Proper application is key to maximizing DE’s effectiveness outdoors. Use a duster or puffer bottle to apply a thin, even layer of DE to affected areas. Avoid applying too much, as this can create a dusty mess and be less effective than a thin, consistent coating. Reapply after rain or if you notice a decrease in effectiveness.
Safety Precautions
While food-grade DE is considered safe, it’s still important to take precautions when using it. Avoid inhaling the dust, as it can irritate the lungs. Wear a dust mask during application, especially when applying large amounts. Keep DE out of the reach of children and pets.
Frequently Asked Questions (FAQs) About Using Diatomaceous Earth Outside
1. How long does diatomaceous earth last outside?
The longevity of DE outside depends on environmental conditions. In dry conditions, it can remain effective for several weeks or even months. However, rain and humidity significantly reduce its lifespan, requiring frequent reapplication, sometimes as often as after each rainfall.
2. Is diatomaceous earth harmful to beneficial insects?
Yes, DE can harm beneficial insects like bees and ladybugs if they come into direct contact with it. It’s best to apply DE in the early morning or late evening when beneficial insects are less active. Avoid applying it directly to flowers or areas where bees are foraging.
3. Can I use diatomaceous earth to control slugs and snails in my garden?
Yes, DE can be effective against slugs and snails. Create a barrier of DE around vulnerable plants. However, remember that moisture will reduce its effectiveness, so reapplication is often necessary, especially after rain or heavy dew.
4. Will diatomaceous earth kill grass?
No, DE will not kill grass. In fact, it can improve soil drainage and aeration, potentially benefiting grass growth.
5. How often should I reapply diatomaceous earth after rain?
Generally, you should reapply DE after any significant rainfall. Even heavy dew can diminish its effectiveness, so consider reapplication if you notice a decrease in pest control.
6. Can diatomaceous earth be used on vegetable plants?
Yes, food-grade DE is safe to use on vegetable plants. Wash vegetables thoroughly before eating to remove any DE residue. Focus application on areas where pests are present, avoiding excessive dusting of edible parts.
7. Is diatomaceous earth safe for pets who spend time outdoors?
Food-grade DE is generally considered safe for pets, but avoid letting pets inhale the dust during application. If your pet ingests a large amount of DE, it could cause digestive upset. Always consult with a veterinarian if you have concerns.
8. Can I mix diatomaceous earth with water to spray it?
While you can technically mix DE with water to create a slurry, it becomes ineffective as an insecticide when wet. The abrasive properties that kill insects require the DE to be dry. Therefore, spraying DE with water defeats its primary purpose.
9. How much diatomaceous earth should I use on my garden?
A little goes a long way. Apply a thin, even layer of DE to affected areas. Avoid creating thick piles, as this is wasteful and less effective. Use a duster or puffer bottle for best results.
10. Does diatomaceous earth expire?
DE does not technically expire. However, it can absorb moisture from the air over time, which may reduce its effectiveness. Store DE in a dry, airtight container to maintain its potency.
11. Can I use diatomaceous earth to control fleas in my yard?
Yes, DE can help control fleas in your yard. Focus on areas where pets spend time, such as dog houses, patios, and grassy areas. Reapplication is crucial, especially after rain or watering. Combine DE with other flea control measures for best results.
12. Where can I buy food-grade diatomaceous earth?
Food-grade DE is readily available at garden centers, hardware stores, feed stores, and online retailers. Make sure to specifically look for “food-grade” DE to ensure it is safe for your intended use.