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Extension Notes: Horticultural oils

Use Horticultural Oils this Winter to Control Spring and Summer Pests

By: Rebecca Konopka
Carter County Extension Agent

Winter probably doesn’t seem like the right time to eliminate pests that will take advantage of your landscape plants next spring. But we need to remember that many problem pests will spend the winter on or near the plants they want to munch on when the weather turns warmer.

One way to get an early handle on problem pests is to use horticultural oils specially formulated for pest control. Horticultural oils suffocate overwintering pests like scale, aphids and certain mites.

These oils are used as a more natural substitute for a traditional insecticide. They are an effective chemical control with minimal environmental impact and usually have little effect on beneficial insects and wildlife. Plus, horticultural oils are safe to humans, don’t have an objectionable odor and usually are inexpensive compared to many other insecticides.

By using horticultural oils on pests in the overwintering stage, you can avoid a potential outbreak later. This can save time because you might not need treatments in the early spring, or at least need fewer applications.

We do offer some words of caution. Don’t apply a horticultural oil during temperature extremes, especially if the temperature is forecast to drop below 40 degrees F the day before or after application. If you wait until later in the year to use a horticultural oil, don’t apply it if the temperature could rise above 90 degrees F. Trees and plants are more sensitive to injury from a horticultural oil under extreme heat or cold.

As with all chemicals, read and follow the label directions. Also, be sure the product is labeled for the plants to which you’re applying it.

Thorough spray coverage is key to an effective application because horticultural oils only work by contacting and covering the target pests. For best results, use high-volume sprays combined with proper pruning practices to allow thorough plant penetration of the spray material.

Proper timing is critical for successfully applying these oils. You should apply them before leaves or flowers show signs of breaking dormancy—before bud break. It usually is in late March or early April but might vary by two weeks or more depending on weather conditions. Wait until as close to bud break as possible before applying horticultural oil sprays.

For more information about, visit or contact the Carter County Extension office. Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expression, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.

Upcoming Events:

  • Berry Plants – The Extension Office is accepting orders through February 27th for strawberry, raspberry, and blackberry plants. Call 474-6686 to request an order form.
  • Northeast Area Livestock Association – February 28th @ 6:00 PM; Speakers: Dr. Wes Whitley, Bluegrass Animal Clinic & Sherri Chapman, Multimin USA; Topic: Livestock Antibiotic Changes
  • Hike & Learn – March 2nd @ 1:00 PM; Carter Caves State Resort Park – Cascade Cave Flashlight Tour
  • Little Sandy Beekeepers – March 7th @ 6:00 PM; Topic: Catching & Relocating Swarms


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