San José, Costa Rica, since 1956
Home Gardening

Diatoms: a pest-control ally from prehistoric times

Here’s a term that will soon become a household word: I’m talking about diatoms.

Many gardeners are familiar with D.E., or diatomaceous earth, because it can be used to control insects in the garden and around the home. I’ve evaded writing about D.E. for the simple reason that it was difficult to find in Costa Rica, but recently a gardener tipped me off to a new source in the country, and I’d like to pass on the good news.

Diatoms are minuet micro-algae that are found in both fresh water and ocean habitats. Their structural geometric designs are truly amazing creations of Nature. Some look like futuristic sci-fi space colonies; could it be that diatoms inspired the designs we see in modern architecture and  media?

Diatoms have unique geometric structures made from silica, which they extract from the water, like corals that build their homes from calcium in the ocean. They are also one of the most important primary producers of the phytoplankton species, providing an estimated 40% of the food for the ocean’s secondary feeders.

As these diatoms bloom and die in lakes and oceans, they form layers of deposits along with silt. All around the world there are ancient deposits of these diatoms which date back as far as 50 million years ago, although most commercial D.E. is from deposits that date back to 13 million years. It was first discovered in 1837 by a peasant in Germany, and was soon found to be an ideal abrasive for polishing metals and jewelry. Later, it was recognized for its ability to be used as a filter, particularly for water purification.

Today it is used widely for many types of filters including industrial uses and filters for swimming pools. It’s even found in some processed foods. Gardeners and farmers also have used it for centuries to control insect pests. It has a unique mode of attack on insects: The tiny diatoms have sharp, pointed surfaces which damage the insect’s exoskeleton and joints, causing dehydration and suffocation.

It is usually applied as a dust to plants during dry periods or in controlled greenhouses, since humid conditions reduce its effectiveness. Lightly sprinkle dry D.E. on the soil’s surface where slugs, centipedes, or other unwanted pests will come into direct contact with the dry particles. Renew after rain or heavy dew. It works well on many types of bugs, including squash bugs, bean beetles, stink bugs, aphids and flea beetles.  Dust your plants that have insect infestations. Perhaps its best use is in the home where it can be applied along the floors, cabinets and closets to eliminate cockroaches, spiders, scorpions, bed bugs, fleas and ants.

Diatomaceous earth is also non-toxic, although you should avoid breathing in the fine powder which can irritate the respiratory tract. Some people have experienced skin irritation when overexposed to D.E. A special class of food-grade D.E. is now used for both human and animals to treat parasites, improve energy, digestion and regularity. It also helps in detoxification and removal of heavy metals. Silica found in D.E. also improves skin, hair and nails, as well as improvement in joints, ligaments and bones.

For more information on D.E. and how you can purchase it in Costa Rica, contact Earth Matters Costa Rica (2494-8992), a small company dedicated to providing natural products for body, health and home.

Read more of Ed Bernhardt’s monthly Home Gardening columns here.

For more information on tropical gardening – naturally – and upcoming Sunday workshops, visit Ed’s website or contact him at thenewdawncenter@yahoo.com. 

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