How to Spread Diatomaceous Earth in Your Garden: A Definitive Guide
Diatomaceous earth (DE) is an incredibly versatile and naturally derived insect control solution. Applying it effectively in your garden involves choosing the right type, understanding optimal spreading techniques, and knowing when and where to use it for the best results against pests.
Understanding Diatomaceous Earth for Garden Use
What is Diatomaceous Earth?
Diatomaceous earth (DE) is a naturally occurring sedimentary rock composed of fossilized remains of diatoms, a type of hard-shelled algae. When crushed into a fine powder, this material becomes a potent yet non-toxic insecticide and soil amendment. Crucially, for garden use, you need to use food-grade diatomaceous earth only.
The Different Types of Diatomaceous Earth
There are two primary types of diatomaceous earth: food-grade and filter-grade. Filter-grade DE, often used in swimming pool filters, is highly toxic and should never be used in gardens or around animals and humans. It undergoes a process called calcination that changes its chemical structure and renders it dangerous. Food-grade DE, on the other hand, is safe for use around humans and animals and is the only type suitable for gardening. It works by dehydrating insects, causing them to die.
Preparing to Spread Diatomaceous Earth
Gathering Your Supplies
Before you begin, gather the necessary supplies. This includes:
- Food-grade diatomaceous earth: Purchase a sufficient quantity for your garden size.
- A duster or applicator: Options include a bulb duster, a shaker, or even a simple sieve.
- Protective gear: Wear a dust mask and gloves to avoid inhaling the fine particles and to protect your skin.
- Water (optional): For creating a wet slurry application.
Identifying Pest Infestations
Before spreading DE, take the time to identify the pests you’re targeting. Diatomaceous earth is effective against a wide range of insects, including:
- Aphids
- Slugs and snails
- Ants
- Flea beetles
- Cabbage worms
- Earwigs
Identifying the specific pest will help you target the application for maximum effectiveness.
Methods for Spreading Diatomaceous Earth
Dry Application
Dry application is the most common method for spreading DE. It is best performed in dry weather, as moisture will reduce its effectiveness until it dries again.
- Using a Duster or Shaker: Fill your duster or shaker with food-grade DE.
- Apply a Light Coating: Apply a thin, even layer of DE to the affected plants, focusing on areas where pests are present. Dust the undersides of leaves, stems, and surrounding soil.
- Repeat as Needed: Reapply after rain or watering.
Wet Application
Wet application involves mixing DE with water to create a slurry that can be sprayed or painted onto plants.
- Mix DE with Water: Mix DE with water at a ratio of approximately 4 tablespoons per gallon of water.
- Stir Thoroughly: Ensure the DE is well-dispersed in the water to prevent clumping.
- Apply with a Sprayer or Brush: Use a garden sprayer or a paintbrush to apply the mixture to plants.
- Allow to Dry: The water will evaporate, leaving a coating of DE on the plant surfaces. Note that the DE is only effective once it is dry, so this method provides initial protection.
Soil Incorporation
Diatomaceous earth can also be incorporated directly into the soil to control soil-dwelling pests and improve soil structure.
- Sprinkle DE on the Soil Surface: Sprinkle DE evenly over the soil surface.
- Incorporate into the Soil: Use a rake or garden fork to gently mix the DE into the top few inches of soil.
- Water Lightly: Water the soil to help settle the DE.
Best Practices for Effective Diatomaceous Earth Use
Timing is Key
Apply DE in the early morning or late evening when beneficial insects are less active. Avoid applying during windy conditions to prevent the DE from being blown away.
Targeting Problem Areas
Focus your application on areas where you have observed pest activity. Pay particular attention to the undersides of leaves, where many insects like to hide.
Reapplication After Rain
Diatomaceous earth is most effective when dry. Reapply after rain or watering to maintain its pest-control properties.
Using DE as a Preventative Measure
Applying DE regularly as a preventative measure can help control pest populations before they become a problem.
Maintaining a Healthy Garden
While DE is effective, remember that it’s just one tool in your gardening arsenal. Maintaining healthy soil, providing adequate watering, and choosing disease-resistant plant varieties are essential for long-term pest control.
Frequently Asked Questions (FAQs)
1. Is Diatomaceous Earth Safe for Pets and Humans?
Yes, food-grade diatomaceous earth is generally considered safe for pets and humans when used as directed. However, it can be irritating to the eyes, nose, and throat if inhaled. Always wear a dust mask and gloves when applying DE.
2. How Often Should I Apply Diatomaceous Earth?
Reapply after rain or watering. For persistent pest problems, apply every 7-10 days until the infestation is under control. For preventative measures, apply every 2-4 weeks.
3. Can I Use Diatomaceous Earth in My Vegetable Garden?
Yes, food-grade diatomaceous earth is safe to use in vegetable gardens. It is an excellent option for controlling pests without using harsh chemicals. Remember to wash your vegetables thoroughly before eating them.
4. Will Diatomaceous Earth Harm Beneficial Insects?
While DE is effective against many insects, it can also harm beneficial insects if they come into contact with it. Minimize the risk by applying DE in the early morning or late evening when beneficial insects are less active and avoid directly dusting flowers where pollinators frequent. Consider using targeted application methods to minimize non-target effects.
5. Can Diatomaceous Earth Be Used to Control Fleas?
Yes, food-grade diatomaceous earth can be used to control fleas in your yard. Sprinkle it lightly on grass, under bushes, and in other areas where fleas may be present.
6. How Long Does Diatomaceous Earth Take to Kill Insects?
Diatomaceous earth typically kills insects within a few hours to a few days, depending on the insect and the level of exposure.
7. Can Diatomaceous Earth Improve Soil Drainage?
Yes, diatomaceous earth can improve soil drainage. Its porous structure helps to aerate the soil and improve water infiltration.
8. What is the Best Way to Store Diatomaceous Earth?
Store diatomaceous earth in a dry, airtight container. This will prevent it from absorbing moisture and clumping.
9. Can Diatomaceous Earth Be Used on Indoor Plants?
Yes, food-grade diatomaceous earth can be used on indoor plants to control pests. Apply it sparingly to the soil surface and leaves.
10. Is Diatomaceous Earth Effective Against Root Knot Nematodes?
While DE won’t eliminate established root knot nematodes, incorporating it into the soil can help to disrupt their lifecycle and reduce their population. Soil solarization and crop rotation are also effective strategies.
11. Can I Use Diatomaceous Earth in Hydroponic Systems?
Generally, no. Diatomaceous earth is not typically used in hydroponic systems as it can clog the system and is not easily dissolved. However, you can sprinkle it around the base of hydroponic plants to prevent pests from climbing onto them.
12. How Do I Know if I’m Using Food-Grade Diatomaceous Earth?
Always check the label. Food-grade diatomaceous earth will be clearly labeled as such. If the label does not specify food-grade, do not use it in your garden. Be especially wary of cheaper, unmarked products, as they may contain harmful filter-grade DE.