by Gabrielle LaTora, Agriculture and Natural Resources Agent
What is neem?
Neem – sometimes called neem oil – is a pesticide derived from seeds of the neem tree (Azadirachta indica), native to South Asian forests. Because neem is derived from a natural source and has action against a variety of insect pests and diseases, it is a commonly used organic pesticide. Despite being OMRI-approved, most neem products are toxic to bees and some to birds and aquatic invertebrates.
Neem works in both chemical and physical ways. Azadirachtin is the main chemical compound that kills pests, a.k.a. the “active ingredient.” By affecting their endocrine (hormone) systems, azadirachtin repels insects, deters feeding, and disrupts insect metamorphosis than killing them directly. These processes take time, so don’t expect neem to kill insect pests outright or stop feeding immediately.
Most neem products use an oil base – this physically kills insects by suffocating them when they become coated in oil. The physical action of oil works best on immature insects. Adults and larger insects are rarely affected. Regular scouting and identification of insects is an important part of an IPM approach and helps you make sure you’re applying your pesticide at the correct time.
What pests and diseases are neem effective against?
Aphids, beetle larvae, caterpillars, lacebugs, leafhoppers, leafminers, mealybugs, spider mites, thrips and whiteflies are commonly listed as pests controlled by neem. Always check the label to make sure your product will work on your target pest.
Neem also inhibits some microorganisms, including viruses, bacteria, and fungi. With some fungal diseases, like powdery mildew, neem prevents fungal spores from germinating on leaf tissue. Neem won’t “cure” a plant that is already infected with a fungal disease, but it can help limit the spread of the disease to healthy tissue. Again, it’s important to be scouting regularly so you can catch an issue early.
Images by Jena Johnson, University of Georgia and David Riley, University of Georgia, bugwood.org.
How you should use neem
Neem products are formulated as ready-to-use sprays, granules, dusts, wettable powders, and emulsifiable concentrates. If you buy a concentrate, make sure to dilute it to the proper concentration and in the right carrier. Always wear the PPE listed on the label.
As an organic pesticide, neem doesn’t last in the environment for long once it’s applied. Microbes and sunlight break it down quickly, so it’s important to get thorough and targeted coverage. For insect pests, early application to immature life stages is more effective – one reason regular scouting and identification is important. For disease management, you actually want to apply neem preventively on a regular basis to protect crops from infection.
Careful around flowering plants when honey bees are active – neem oil is toxic to bees. If crops or weeds are flowering in the vicinity, consider applying in the evening or early morning when bees are not foraging.
Common pitfalls to avoid
- Neem oil can burn foliage. Do not use on recent transplants or stressed plants. Though plants must be completely covered with neem oil for the pesticide to be effective, it is a good idea to spot test a small area first.
- Neem is not effective against all insects and diseases. Neem is not recommended for larger “true bugs,” like leaffooted bugs, harlequin bugs, and squash bugs, or other common insects, such as squash vine borers or grasshoppers. There is mixed data for neem’s effectiveness on flea beetles and stink bugs. Neem is not effective for some diseases, such as late blight in tomatoes. It’s very difficult (for me, at least) to remember all these specifics, so just check the label for your target pest before you apply.
- Neem is a pesticide. In an IPM approach, pesticides should be used as a last resort after 1) the pest or disease has been correctly identified, 2) management options have been carefully reviewed, and 3) cultural, mechanical, and biological controls have been implemented. Your Extension agent can help you with these steps.
- Always follow the label instructions. Application rate, frequency, and other instructions are designed to tell you the safest and most effective way to apply the product. Why would you want to mess with that? Make sure to check that the plant AND target pest/disease are listed on the label. If not, that product will not work for your particular issue and you’re wasting time and money and introducing unnecessary pesticides into the environment.
If you ever have questions about a pesticide, course of action, insect pest, or disease, don’t hesitate to contact your county Extension agent.
Learn More
- Neem: A Novel Biocide for Pest and Disease Control of Plants (Journal of Chemistry)
- What should neem be used for on plants? (UNH Extension)
- Neem Oil Fact Sheet (National Pesticide Information Center)
- Southeastern U.S. Vegetable Crop Handbook 2026 (the GOAT for veg production questions)
- Common neem oil products (Arbico Organics)
