Dormant Oil 2025 – IPM Pest Advisories

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Insects and Diseases Affected by an Oil or Copper Spray

Click on an image for caption information.

Aphids on bud — Aphids overwinter as eggs in fruit trees.

Pear psylla damage — Pear psylla causes browning of pear foliage. It overwinters as eggs near buds.

San Jose scale is an immobile insect that feeds on bark and fruit. Oil targets the overwintering nymphs on the bark.

Cankerworm larva — Fall cankerworm overwinters as eggs that can be suffocated by oil. The larvae can feed on fruit and leaves.

Peach twig borer on fruit — Peach twig borer feeds on succulent twigs and ripening fruit. It overwinters on the bark, so the oil will smother the tiny larvae.

Blister mite damage — Blister mites overwinter in bud scales. Their feeding causes brown spots to form in the summer.

Pear psylla eggs right underneath the bud of a branch. — Pear psylla eggs are laid near buds in early spring. If this was a problem last year, apply oil twice, spaced about 7 days apart.

Brown mite symptoms — Brown mite is a cool-season mite that is uncommon. It overwinters as eggs on the tree.

Fire blight canker ooze. — Fire blight infections on bark will ooze bacteria in spring. Copper prevents the bacteria from multiplying.

Dormant oil does not control: codling moth, spider mites, borers, cherry fruit fly, powdery mildew.

Dormant Oil Spray Details

For those that live in northern Utah, the time to apply dormant oil is approaching, and the warm weather this week could be an option. However, there is still plenty of time for this application on fruit trees through mid-April.

The “dormant oil” spray is applied after trees break dormancy. The reason to wait for bud swell or budbreak is because this timing coincides with increasing activity of the overwintering insect stages, such as the hatching of aphid eggs, scale nymphs starting to feed, and peach twig borer larval feeding. If applied too early, the oil will not work as well on these pests.

In the warmest areas of Utah, trees are blooming or past bloom, so you may have already applied your dormant oil.

Should I Spray at All?

If your fruit trees have not been affected in the past by the pests in the image gallery shown above, you can skip the oil application.

When Should I Spray?

There are two factors to consider for determining when to spray: the bud stage of your own fruit trees and weather conditions.

Bud Stages

The window for application extends from bud swell to pre-bloom, usually a period of several weeks, depending on the tree. The images below show examples of bud swell or budburst. Your application should be applied in the range just before or soon after the buds of your trees resemble these.

Click here for pictures of all fruit bud stages (along with temperatures at which frost damage could occur).

Weather Conditions

Only apply oil if temperatures remain above freezing (ideally above 40°F) for 12 to 24 hours after application.
Ideally, oil should be applied on a clear, non-windy day in the 50° to 70°F temperature range.
Do not apply if rain is predicted within 24 hours. This will help give the oil time to work.
If rain is predicted farther out than 24 hours, then you are OK to spray.

How to Spray

Commercial growers

Oil should be applied at a rate of 2-3%, which is 2-3 gallons per 100 gallons of water.
(Optional) Mix oil with an insecticide such as Warrior or Asana to help improve knockdown of overwintering pests.
When spraying apple or pear trees, it is OK to mix in copper for fire blight.
Thoroughly cover all cracks and crevices of the tree bark and buds.

Backyard growers

Oil is sold as a concentrate, so it must be mixed at the proper rate with water before application. Check the label of your product, but most oils are applied at a rate of 2% to 3%. The higher rate is more effective but has a greater chance of causing bud/leaf damage if applied in warm temperatures or at a late growth stage.

2% mixture is 5 TBS oil per gal water
2.5% mixture is 6 TBS plus ¾ tsp per gal water
3% mixture is 7.5 TBS per gal water

If you are not growing organically, and aphids or scale have been a serious problem and oil alone has not worked in past years, consider mixing the oil with the appropriate rate of an insecticide, such as Spectracide Triazicide, GardenTech Sevin, or Malathion.

When spraying apple or pear trees, it is OK to also mix in the proper rate of copper to help prevent fire blight bacteria from multiplying.

Make sure you thoroughly cover all cracks and crevices of the bark and buds.

More details about oil

There are plant-based oils and petroleum-based oils. For the dormant oil application, the petroleum-based oils work the best, although canola oil is the best plant-based option.

Petroleum-based oils – There are many brands, and they all work the same. Examples include All Seasons Horticultural Oil, Monterey Horticultural Oil, Gordon’s Dormant Oil Spray, Ortho Volk Spray Oil, Hi Yield Dormant Oil, etc.
Plant-based oils – One example is Natria Multi-Insect Control (canola oil), but there are many others. Neem oil is not as an effective option for the dormant application.

Dormant Copper Products

Copper can be used on apple and pear as a management tool for fire blight. Based on research from Colorado State University, we are not recommending copper as a dormant application on peach (it causes tiny wounds that can be substrates for the pathogen that causes cytospora canker).

Ingredient	Commercial Options	Residential Options	Comments
basic copper sulfate	Cuprofix Ultra Disperss; Basic Copper Sulfate; C-O-C-S		Effective, but should only be used before leaf emergence or in the fall
copper oxide	Nordox
copper hydroxide	Kocide; Champ; Badge SC; NuCop; Previsto		Previsto has a low copper concentration
copper diammonia diacetate complex		Monterey Liqui-Cop
copper octanoate (soap)	Cueva	Gardens Alive Soap Shield; Bonide Liquid Copper Fungicide; Natural Guard Copper Spray; Espoma Copper Soap	Has lower metallic copper concentration; safer on plants; effective
copper sulfate pentahydrate	MasterCop; Phyton		Not as effective as a dormant application.