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 No matter how well you apply planting practices that reduce pest invasion, some pests will likely still get through to your plants. Fortunately, other organisms have been battling the same culprits much longer than we have—and they’ve developed methods to control them that we can learn from. Organic pesticides utilize these naturally occurring compounds; thus, they are prime weapons in the arsenal of pest-control solutions.
Although organic pesticides come from natural sources, they are chemicals and should be treated like any pesticide. Terms such as “organic” or “all natural” do not guarantee that a product is safe for you or the environment—some do pose risks to people, animals, aquatic life or beneficial insects. Before buying, carefully read the label for information on toxicity, active ingredients, instructions and precautions for application, environmental hazards, first aid and proper disposal.
Know Thy Enemy
Before applying a pesticide, take the time to correctly identify the culprit you are battling, since many of the organic products target particular pests. Traps and lures will help identify the problem insect, reveal the level of infestation and possibly even help control them. Some will capture any insect, others use pheromone-scented lures to trap specific ones. Once you know what is causing the problem, (your county extension office can usually help in the identification of insects) the proper, targeted solution can be implemented.
Organic Pesticides
The Environmental Protection Agency (EPA) has registered close to 200 natural pesticide active ingredients in almost 800 products and maintains a database of all certified products. The main categories of organic pesticides include botanicals, microbials, oils, soaps and minerals.
Botanicals
The most popular of these plant-derived products are: neem, pyrethrins (synthetic versions called pyrethroids are more toxic), sabadilla, rotenone, ryania, citrus-oil d-limonene and plant-oil extracts. Most botanicals break down in sunlight or water and require frequent applications. Refer to the additional-resource links at the end of this piece for specific information on the insects each controls and any related safety issues. Here are the highlights:
- Neem has become a popular product to control a variety of insects due to its low toxicity to mammals, fish, birds and beneficial insects.
- Pyrethrins and rotenone should be kept away from water sources since they can harm aquatic life.
- Care should be taken with pyrethrins, sabadilla and rotenone because these broad-spectrum products could harm bees and other beneficial insects.
- Citrus-oil d-limonene, made from citrus extracts, is a nontoxic contact poison used to control fire ants, fleas, ticks and mites.
- A variety of nontoxic plant-oil extracts that can be used as insect and animal repellants are available.
Microbials
- Contain extracts from microorganisms.
- Each targets a particular pest.
- Their specificity results in low toxicity for humans, animals and plants.
- Care is required to select the appropriate one.
- The most widely used, Bt is a compound from the bacteria Bacillus thuringiensis that controls certain types of caterpillars, beetle larva, mosquitoes and flies. There are many different formulations of Bt; all have low toxicity with minimal effects on beneficial insects.
- Spores from Beauveria bassiana, and the fermentation byproduct spinosad are fungi-based products that can control aphids, beetles, mites, fruit flies and caterpillars. Both have low toxicity and are considered safe for the environment except that they may harm bees.
Oils and Soaps
Included here are insecticidal soaps made from potassium salts of fatty acids, and horticultural oils that are petroleum, vegetable-oil or fish-oil based. Both are sprayed directly on plants to smother damaging insects such as aphids. These could harm beneficial insects if they are hit with the spray, and must be applied regularly since they break down fairly quickly.
Minerals
- Copper and sulfur are used to control several bacterial and fungal diseases.
- Nontoxic potassium bicarbonate and sodium bicarbonate (baking soda) can be combined with oils to control certain fungi.
- Diatomaceous earth, a powder made from the fossilized shells of single-celled organisms called diatoms, is used to control a variety of insects in gardens and homes, and is generally considered safe unless inhaled.
- Kaolin clay is a nontoxic, naturally occurring pest-repelling mineral that can be applied to form a barrier.
Organic vs. Synthetic
At the outset, the costs for organic products are similar to synthetic versions, but their more frequent applications can lead to a higher expense. Synthetic pesticides are generally more effective, but this enhanced killing power can lead to serious health and environmental issues.
Organic pesticides, while generally a safer option than synthetic chemicals, need to be selected, handled and applied with care. They can be an effective way to control pests indoors and out, yet any health or environmental effects should be considered before use in a natural pest-control regimen. Part 3 of this series on natural pest control will provide a pesticide-free strategy employing beneficial organisms.
See Part 1: Planting Practices That Reduce Pest Invasion
See Part 3: Replacing Pesticides with Insects, Worms, Birds, Bats and Other Beneficial Organisms
Additional resources:
Information on Specific Organic Pesticides
Database of Natural and Synthetic Pesticides
Recommendations for Products Based on Problem Insects
Organic Solutions for Problem Insects
How to Plant a Vegetable Garden
What You Need to Know to Become an Urban Farmer
Breaking Down the Bones: How to Compost Meat and Other Animal Products
How to Compost and Build a Compost Heap
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