Neem Oil for Plants

Neem Horticultural Oil

• Horticultural oils are highly refined oils mixed with emulsifiers and water and sprayed onto plants to control plant pests. Oils are nontoxic to plants and most animals but can block insects' breathing holes, suffocating them, or interfering with fatty acid metabolism to poison them. Horticultural oils may also disrupt insect feeding, slowing killing them, but also interfering with their ability to transmit viruses to plants. Some oils are also effective in controlling powdery mildew. At least one commercial product uses neem oil extracts, largely free of the active insecticidal ingredient azadirachtin and related compounds, as an effective horticultural oil fungicide and insecticide.

Neem Oil Insecticides

• Insecticidal neem-oil compounds with the active ingredient azadirachtin make an effective insecticide and fungicide. They are naturally biodegradable and typically harmless to humans, animals, fish and desirable insects including butterflies, ladybugs, bees and other pollinators. Even earthworms are unaffected by neem in the soil. A broad-spectrum botanical pesticide and fungicide, azadirachtin effectively controls thrips, fungus gnats, whiteflies, aphids, caterpillars, beetles, mushroom flies, mealybugs, leafminers and gypsy moths.

Neem Oil Precautions

• Use neem oil products only as directed, and only on recommended plants. Plants that may show sensitivity include Japanese maples, Alberta dwarf spruce, blue spruce, ornamental olives, some roses and carnations, fuchsias, hibiscus and impatiens. Spray in the cool of the evening, or when temperatures are less than 80 degrees F. Also spray when plants are in the shade and there is little wind. Don't use neem oil within two weeks after using any sulfur product.