What Is Neem Oil?
Derived from the neem tree, neem oil has been used for centuries to control pests, as well as in medicinal and beauty products. Some neem oil products you’ll find for sale work on disease-causing fungi and insect pests, while other neem-based pesticides only control insects. Check the product label carefully to ensure you get a product that’ll be effective on your specific pest problem. Neem oil pesticides also can differ in how they’re formulated for application. Some neem products ($11, The Home Depot) are labeled “ready to use” and often come in a spray bottle you can use to apply them. Other neem oil products are labeled “concentrate” and require some prep before you can use it on your plants. Concentrated products need to be mixed with a certain amount of water and common dish soap, then poured in a spray bottle prior to application. Follow the product’s mixing directions carefully. Ready-to-use formulations are quick and easy to use; concentrated products are generally less expensive than their grab-and-go counterparts.
How to Use Neem Oil
First, identify the insect, mite, or fungal disease you’re battling. Pesticides are labeled with specific pests they control. Neem oil is labeled for use on soft-bodied pests such as aphids, beetle larvae, caterpillars, leaf hoppers, mealybugs, thrips, spider mites, and whiteflies. Applying neem oil to squash bugs, for example, is useless because the product isn’t effective against these pests. Neem oil works by suffocating insects or disrupting how they feed. The pest must be present when the oil is sprayed on the plant to be effective. When applying neem oil, cover all parts of the plant. Make sure to spray the undersides of leaves where pests can hide and lay eggs. Unlike many pesticides that continue working after application, neem oil has no effect after it dries (it’s actually biodegradable, breaking down quickly into harmless components). Note that neem oil doesn’t discriminate between aphids and bees, butterfly larvae, or any other good guys. It won’t harm birds, but it’s toxic to fish and other aquatic creatures. Avoid harming beneficial insects and water habitats by applying the spray carefully, following all label directions for application. Some neem oil products also control fungal diseases such as powdery mildew and blackspot. It combats fungi by preventing new spores from germinating. Neem oil won’t completely get rid of these diseases, but it can reduce the spread enough that your plants can continue growing.
Which Plants Can You Treat?
Neem oil is labeled for use on all types of plants, from houseplants to flowering landscape plants to vegetables and herbs. Before treating a plant with neem oil for the first time, it’s always a good idea to test the product on a single leaf. Check for signs of stress after a day has passed. It’s generally best to avoid using neem oil on young plants or transplants because it can burn tender new growth.
When to Apply Neem Oil
Aim to apply neem oil in the early morning or late evening. Beneficial insects are usually less active at these times, making them less likely to come in contact with the pesticide. Applying neem oil early in the day or later in the evening also helps prevent leaf damage; mid-day high heat and bright sunlight can cause neem oil to burn leaf tissue. You can use neem oil any time of year, whenever pest problems appear. In winter, it’s particularly useful for controlling houseplant pests such as whiteflies. In summer, you can use neem oil on veggie and herb crops up to the day of harvest. Just make sure to wash produce thoroughly before eating. Neem oil takes time to work. It might be two days or more before you see a reduction in damage or fewer live insects. You may need to reapply your neem product every three or four days, especially after a rain, to completely get rid of your target pests.
