For frustrated gardeners, sometimes the best way to fight the horror of slugs present is with the ghosts of critters past. The use of pulverized tiny sea creatures called diatoms can actually keep slugs, snails and other pests from munching on your veggies and ornamentals. This nontoxic material, known as diatomaceous earth (DE), is a desiccant; it kills slugs and other pests by destroying their waxy, protective outer layers, causing them to dry out and die.
Purchase bagged DE in 1- or 2-pound bags from a hardware or garden supply store. You may even find it at a feed store, as farmers often give it to cattle to kill internal parasites.
Examine your garden’s problem areas. Learn to identify pests and the damage they inflict by sight. Knowing not just what’s getting eaten but who’s doing the eating will help determine how and where to apply the DE.
Put on gloves, goggles and a dust mask. While nontoxic, DE’s sharp, tiny particles can irritate eyes, lungs and skin.
Following the directions that came with the tools, prepare your duster and/or garden syringe. The garden syringe needs to be filled with a mixture of water and DE; the package instructions should give you a precise measurement. The duster can be loaded with the dried DE or with a water-DE slurry.
Inspect trees and shrubs for borer damage. Tiny holes in the bark will often be weeping sap or a kind of sawdust known as frass.
Fill any borer holes by injecting them with the water-DE mixture in your garden syringe. Seal the holes with putty or some of the frass.
Slither on over to your slug-damaged plants. Working in small “puffs,” use the duster to make a border of DE directly on the ground to deter these crawling pests. Apply a thin circle around the base of individual plants or entire patches, depending on how widespread the problem is.
Finally, hover over any plants being attacked by flying creatures, especially aphids, thrips and mites. Dust DE directly onto the leaves, both the tops and undersides, if possible. Avoid flowers or blossoms.
Things You Will Need
- Diatomaceous earth
- Portable dusting tool
- Garden syringe (optional)
- Dust mask
- Always apply diatomaceous earth in dry, windless conditions. DE loses effectiveness on damp foliage and wet ground. Reapply after each rain shower and once a week during humid weather.
- Diatomaceous earth doesn't distinguish being the "bad guys" and the "good guys" in your garden, so be selective about where you apply it. If large holes appear in your lettuce, for example, then focus on the lettuce patch---not the entire surrounding vegetable garden. Desiccants like DE can destroy electric engines, so make sure to use it sparingly where you'll be using a leaf blower or similar tool. Do not buy the type of diatomaceous earth used for pool cleaning. The two products are prepared differently, and pool-grade DE contains chemical additives.