Oils work very well on most plants, however, always check the labeling before applying them. Applying a “dormant oil” helps kill off any wintering insects like mites, scale, and give aphid control without harming the plant. As a fungicide, this product interferes with the fungal pathogens ability to attach to the host. Unfortunately, they also kill off any beneficial insects as well. Dormant oil now refers to the time of application rather than to any characteristic type of oil. You don’t want to apply too early though, since the insects need to be active and breathing, in order to be affected. Marie Iannotti is an author, photographer, and speaker with 27 years of experience as a Cornell Cooperative Extension Horticulture Educator and Master Gardener, How Horticultural Oils Work as Insect Control. Mix the oil with water and a little Dawn dish soap into a sprayer or a spray bottle and apply on plants struggling with insect issues. Contact with the pest must be made for the oil to be effective. Not a pretty picture, but remember that insects, like aphids, carry diseases from plant to plant by feeding. The oils don’t harm the plant, just the bugs. Most horticultural oils are refined from crude oil. Unfortunately, oils will harm both the good beneficial insects and the bad insects, so take care and evaluate the situation prior to using horticultural sprays. In addition to timing and thorough application, it’s also important to read and follow the label instructions carefully. They also cannot be used as preventative treatments since they do … Fall Horticultural Oil Application Autumn is an excellent time to apply horticultural oil. What can I apply Horticultural Oil? In order for oils to work effectively, insects need to be totally covered. When it comes to pest or insect control, you’ll find several types of oil to use which can eliminate garden pests like spider mites on your fruit tree and shrubs. ★Requires purchase of annual plan. Using Orange Oil to Treat Dry Wood Termites, How to Control Japanese Beetles in Your Lawn and Garden. Ever since the mid 80’s when I worked extensively with oils, I have been a proponent of their use. Make every effort to eliminate pests with other methods, such as neem oil, prior to seeking out horticultural oil such as insecticides or biorational pesticide. Fall Horticultural Oil Application Autumn is an excellent time to apply horticultural oil. You must remember not all insects are pests. The term “dormant spray”, refers to the proper timing to use the oil and not the kind of oil utilized. Always refer to the label for application directions. Application rates vary according to the season, but “horticultural oil” has become the common usage term. Fruit trees posed a unique problem because they were so pest-prone and yet you couldn’t just spray with any insecticide, because it’s an edible product, and you couldn’t kill off all the insects, because you needed the good guys for pollination or there would be no crop. We'll respect your privacy and unsubscribe at any time. Using homemade horticultural oils to kill plant scale and other soft insects on woody ornamental plants make for a lethal combo. During the dormant period, spray Horticultural oil when the temperature is above 40 degrees F and when freezing will not occur before the spray can dry. Dormant oils were further refined to produce lighter-weight oils that can be applied during the growing season, without harm to many plants. This usually means small, immobile or slow moving pests that are exposed on the surface of the plant at the time of application will be controlled. 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