Apply Neem Oil 3n1 as needed. There are many things you can put on the soil. Spraying Hydrangeas. Correct Dose for Neem Oil . Spraying is important to the survival of your plants. Rust: This fungal disease looks like rust colored spots on the underside of leaves. In one study, researchers discovered that a one percent neem oil treatment was effective in managing powdery mildew on hydrangeas, lilacs and phlox. NOTE: This is part 9 in a series of 10 articles. You can also mix it with insecticidal soap for a double whammy. It only targets leaf-sucking and chewing insects. Synthetic pesticides creep away from the sprayed areas to create “death zones” that can kill beneficial insects as well as other animals. Because oil and water tend to separate, you’ll need to keep your solution well stirred. Neem oil is a vegetable oil that has a number of positive effects on gardens and lawns. One of the most observable uses is in the control of powdery mildew on plants such as peonies, zucchinis and cucumbers. Neem oil insecticide, Safer® Brand Neem Oil Ready-to-Use spray, does not create a dead zone around treated plants, trees or shrubs like other synthetic insecticides can. Powdery mildew: While this doesn’t usually kill hydrangeas, it can cause leaves to drop. 4. Neem oil contains both azadirachtin and the oil, so it has the widest range of control, but if you want to control aphids, scale or adults, you only need clarified hydrophobic neem oil which is less expensive. The oil comes from the seed of the meliaceae tree, once native to India but currently grown around the world in warm climates. Neem oil is recommended as an organic insecticide and fungicide. I’ve seen it work on other slug-like insects such as pear slugs, but those aren’t true slugs. Neem oil concentrate is usually mixed with water and sprayed on both sides of plant leaves. Things To Put On The Soil. To handle potential diseases and pests, reference the guidelines below to know what you should spray, and when you should use it. Look for a gray, powdery coating on foliage. The oil acts as a pesticide and fungicide and carries no ill effects for people or pets. Assuming you use a product with 2,000 ppm azadirachtin, the common dilution would be one ounce per gallon (8 ml/l). Neem oil is bottled in different concentrations, so follow the instructions on the package to get the right proportions of oil to water. There are a number of studies that show its effectiveness for various insect and disease problems. Neem oil prevents the germination and penetration of some fungal spores. Neem oil. For a complete background on how to grow hydrangeas, we recommend starting from the beginning. The picture on the left shows a peony beginning to develop powdery mildew. Remove and destroy any affected plant parts. More than 60 insect pests may be … Some people have had success using neem oil on plants to deter slugs and snails, but it doesn’t appear to be the most effective option.