How Often to Apply Diatomaceous Earth? A Definitive Guide
The frequency of diatomaceous earth (DE) application varies drastically depending on the intended use – pest control, animal feed supplementation, or garden enrichment – and the environmental conditions. Generally, for pest control, reapplication is necessary after rain or heavy dew, while for animal feed, daily mixing with feed is standard practice.
Understanding Diatomaceous Earth
Diatomaceous earth (DE) is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It is composed of the fossilized remains of diatoms, a type of hard-shelled algae. Two primary types exist: food grade and filter grade. Only food grade DE should be used for applications involving consumption by humans or animals, or in areas where human or animal contact is likely. Filter grade is used in swimming pool filters and other industrial applications and is not safe for consumption or direct contact due to processing methods.
Food Grade vs. Filter Grade DE
The crucial distinction between food grade and filter grade DE lies in its processing. Food grade DE undergoes minimal processing, retaining its structure and purity. Filter grade DE, on the other hand, is calcined (heated to high temperatures) to alter its structure and improve its filtering capabilities. This process also renders it unsafe for ingestion or direct contact, potentially causing respiratory irritation. Always ensure you are using food grade DE for intended purposes involving consumption or proximity.
The Mechanism of Action
DE works primarily through physical desiccation. The microscopic, razor-sharp edges of the diatom fossils abrade the waxy outer coating of insects, causing them to lose moisture and eventually dehydrate and die. This mechanism is most effective in dry conditions. While effective against many insects, DE poses no threat to mammals and is generally considered safe when used as directed.
Application Frequency: Pest Control
For pest control, the key factor dictating the frequency of application is the persistence of the DE in its effective state. Water renders DE ineffective as it clumps the particles together, eliminating their abrasive action.
Indoor Applications
Indoor applications of DE for pest control, such as for fleas, ants, or bed bugs, require less frequent reapplication. Once the area is treated, the DE can remain effective for several months, provided it stays dry. Reapply only if:
- The DE has been disturbed or vacuumed.
- New pest activity is observed.
- The DE has become damp.
A light dusting is often sufficient; avoid creating visible clouds of dust.
Outdoor Applications
Outdoor applications are significantly more challenging due to the elements. Rain, heavy dew, and even strong winds can diminish the effectiveness of DE.
- General Garden Pest Control: Reapply after each rainfall or heavy watering. Consider applying in the early morning when dew is present to help the DE adhere to plants, but be aware that this reduces its immediate effectiveness. Aim for application every 7-10 days in dry weather.
- Specific Infestations: For focused infestations, reapply more frequently, especially if the affected area is exposed to the elements. Consider creating barriers of DE around vulnerable plants to prevent pests from reaching them.
- Soil Amendment: If using DE as a soil amendment to deter soil-dwelling pests, incorporate it into the soil at planting. Reapply every few months or annually, depending on the soil type and pest pressure.
Application Frequency: Animal Feed Supplementation
Food grade DE is sometimes added to animal feed as a supplement, primarily to control internal parasites and improve overall health. The recommended application frequency is daily.
Mixing with Feed
Mix the DE thoroughly with the animal’s feed according to the manufacturer’s recommendations. The dosage varies depending on the animal species and size. Consult with a veterinarian or animal nutritionist for specific guidance.
Continuous Use
DE is often used continuously as a preventative measure. While generally considered safe for long-term use, it’s essential to monitor the animal’s health and consult with a veterinarian if any adverse reactions occur. Some studies suggest that continuous use can lead to mineral depletion, so supplementing with a high-quality mineral supplement may be beneficial.
Application Frequency: Other Uses
Beyond pest control and animal feed, DE has other potential uses.
Filtration
Filter grade DE is used in swimming pool filters and other filtration systems. The frequency of backwashing or filter replacement depends on the system and the amount of debris being filtered. Follow the manufacturer’s instructions.
Desiccant
DE can be used as a desiccant to absorb moisture and prevent mold growth. The frequency of reapplication depends on the humidity levels and the effectiveness of the DE in absorbing moisture. Replace the DE when it becomes saturated.
FAQs about Diatomaceous Earth Application
Here are some frequently asked questions about applying diatomaceous earth:
1. How long does diatomaceous earth take to kill insects?
Typically, DE can kill insects within 24-72 hours of contact. However, the speed depends on the insect species, size, and the extent of contact with the DE. Smaller insects dehydrate faster than larger ones.
2. Is it better to apply diatomaceous earth wet or dry?
DE is most effective when applied dry. Wetting it temporarily reduces its abrasive action, delaying its efficacy. While a light mist of water can help the DE adhere to surfaces, it’s crucial to allow it to dry thoroughly for optimal results.
3. Can I use diatomaceous earth on my pets?
Yes, food grade DE can be used on pets to control fleas and ticks. Lightly dust the pet’s fur, avoiding the eyes and nose. Always use food grade DE and observe your pet for any adverse reactions. Topical treatments are generally considered more effective.
4. How much diatomaceous earth should I use in my garden?
Use a light dusting of DE on plants, focusing on areas where pests are prevalent. Avoid over-application, as it can smother beneficial insects. For soil amendment, incorporate 1-2 cups of DE per 10 square feet.
5. Is diatomaceous earth harmful to humans?
Food grade DE is generally considered safe for humans when used as directed. However, inhaling DE dust can irritate the lungs and respiratory tract. Wear a mask when applying DE, especially in enclosed spaces. Avoid contact with eyes.
6. Can diatomaceous earth kill bed bugs?
Yes, DE can be effective against bed bugs. Thoroughly dust cracks, crevices, and other areas where bed bugs hide. Reapply every few days until the infestation is controlled. Remember, thoroughness is key.
7. Does diatomaceous earth kill ants?
Yes, DE can kill ants by disrupting their exoskeleton and causing dehydration. Dust ant trails and entry points to control ant infestations.
8. How long does diatomaceous earth last in storage?
DE has a very long shelf life if stored in a dry, airtight container. It can last for several years without losing its effectiveness.
9. Can I mix diatomaceous earth with water and spray it?
While you can mix DE with water for spraying, it’s not the most effective method. The abrasive action of the DE is reduced when wet. If spraying, use a fine mist and allow the DE to dry thoroughly. Ensure constant agitation to prevent settling.
10. Is diatomaceous earth safe for bees?
DE can be harmful to bees, as it can damage their exoskeletons. Avoid applying DE directly on flowers or in areas where bees are actively foraging. Apply with extreme caution and only when necessary. Consider alternative pest control methods that are less harmful to pollinators.
11. Can diatomaceous earth be used in aquariums?
While some advocate for using food grade DE in aquariums to filter water or control algae, this is generally not recommended. DE can alter the water chemistry and potentially harm aquatic life. There are safer and more effective filtration methods available for aquariums.
12. Where can I buy diatomaceous earth?
Food grade DE is widely available at garden centers, hardware stores, online retailers, and feed stores. Ensure you are purchasing food grade DE specifically for your intended use. Read product labels carefully.