About Dormant Oil

 

Dormant Oil: Winter Pest Control

 

It’s not just your plants and trees that may be dormant this time of year—some insect pests are overwintering, too! Certain pests survive the winter as eggs, immature stages, or adults tucked into bark crevices and other protected areas.

Horticultural oil can be an effective tool for managing some of these overwintering pests. The oil works primarily through direct contact, coating and suffocating susceptible insects, mites, and eggs. It does not create a lasting coating that prevents future insects from feeding, so thorough coverage and proper timing are important.

 
 

What Does Dormant Oil Control?

 

Dormant or horticultural oils can be especially useful on certain fruit trees and ornamental plants for managing pests such as scale insects, mites, aphids, and their overwintering eggs or immature stages.

However, the pests controlled and the plants that can safely be treated depend on the particular product. Always check the label to make sure both your plant and the pest you’re targeting are listed.

 
 

When Should You Apply Dormant Oil?

 

Timing matters! “Dormant oil” doesn’t necessarily mean there’s one specific winter date when every plant should be sprayed.

Depending on the plant, pest, and product, horticultural oils may be applied during dormancy or during the delayed-dormant period as buds begin to swell but before new growth has fully emerged.

Weather conditions matter, too. Avoid applying oil when freezing temperatures, rain, or other unsuitable conditions are expected within the period specified on the product label. Temperature restrictions vary by product, so follow the label rather than relying on one universal temperature range.

 
 

Apply It Carefully

 

Dormant oil works through contact, so thorough coverage of the bark, branches, twigs, and other areas where the targeted pest is overwintering is important.

Be careful around nearby plants. Some plants may be sensitive to horticultural oils, and oils can also injure plants when applied under the wrong conditions or at an improper concentration.

Avoid spraying stressed plants, and don’t assume that nearby annuals or other landscape plants can safely receive overspray. Protect surrounding plants as directed by the product label.

Horticultural oils can also affect beneficial insects that are directly contacted by the spray, so avoid unnecessary applications and treat only when you have identified a pest that warrants control.

 
 

Identify the Pest First

 

Before spraying, take a close look at your plants and determine what you’re actually treating. For pests such as scale, old coverings and sooty mold can remain visible even after the insects are dead, so what looks like an active infestation may not always be one.

The best treatment—and the best time to apply it—depends on the pest you’re dealing with. Identify first, treat second, and always follow the current product label.