When I read about organic gardening, I see a lot of references to neem oil. What is it, and how do I use it in my garden? -Sherry

Neem oil is made from the seeds of the neem tree (Azadirachta indica), which is native to India. Since ancient times, the neem tree has been prized as a sacred remedy and important ingredient in Ayurvedic medicine. In the garden, neem oil boasts a powerful insecticidal ingredient, azadirachtin, which makes it a great organic choice for controlling a variety of problems.

Uses for Neem Oil

Neem oil can be used to treat a number of garden ailments, including:

• Insects: Neem oil kills or repels many harmful insects and mites, including aphids, whiteflies, snails, nematodes, mealybugs, cabbage worms, gnats, moths, cockroaches, flies, termites, mosquitoes, and scale. It kills some bugs outright, attacks the larvae of others, and repels plant munchers with its bitter taste.
• Fungus: Neem oil is also effective in preventing fungal diseases such as black spot, anthracnose, rust, and mildew.
• Disease: As if that wasn’t enough, neem oil also battles viruses that can harm plants.

Advantages of Neem Oil

Neem oil is a popular choice in organic gardens because it is:

• Nontoxic: As long as it isn’t sprayed directly on them, neem oil is nontoxic to beneficial garden insects such as predatory wasps, honeybees, earthworms, ants, spiders, ladybugs, and adult butterflies. Neem oil is considered nontoxic to humans, birds, and other animals as well (see below) and can be used on fruits, vegetables, and flowering plants.
• Organic: Neem oil is plant based and easily available from organically grown neem trees.
• Biodegradable: Neem oil breaks down quickly and leaves no lasting residue.

How To Apply Neem Oil

Neem oil concentrate is usually mixed with water and sprayed on both sides of plant leaves. Because oil and water tend to separate, you’ll need to keep your solution well stirred. You can also mix it with insecticidal soap for a double whammy. Neem oil is bottled in different concentrations, so follow the instructions on the package to get the right proportions of oil to water.

Other Uses for Neem Oil

If you’re concerned about the safety of neem oil compared to other products in your garden, consider that neem is often used as an ingredient in:

• Cosmetics
• Shampoos (including pet shampoos for flea/tick control)
• Natural insect repellents
• Alternative medical remedies for antiseptic, antiviral, antifungal, and anti-inflammatory uses

The only health cautions for neem oil relate to actual consumption of the oil, and garden use does not appear to pose any known health hazards. As with any chemical—organic or synthetic—use neem oil only in moderation when needed, and wash all veggies and plants thoroughly before eating.

Further Information

• Material Fact Sheets: Neem (Cornell University)
• Azadirachta indica: One Tree’s Arsenal Against Pests (Colorado State)

Tags: , Neem oil