What Is Dormant Oil?
Dormant oil is a refined horticultural oil used on trees and shrubs during late winter when plants are still dormant. Its purpose is preventative: it smothers overwintering eggs and insects such as scale, mites, aphids, and other pests that could harm fruit trees and roses as new growth begins.
Because landscape and orchard pests hide in bark crevices and buds during winter, applying dormant oil before buds swell gives gardeners the advantage of reducing pest populations before they become active in spring.
Why Apply Dormant Oil to Fruit Trees and Roses
Fruit trees and roses can host a variety of pests that overwinter on stems, bark, and buds. These include scale insects, spider mites, aphids, and other soft-bodied pests that hide through winter. Dormant oil works by coating insect eggs and overwintering insects with an oil film that blocks their ability to breathe, effectively reducing pest pressure before new growth emerges.
When applied properly, dormant oil is both safe and effective and can reduce the need for stronger chemical insecticides later in the season. Dormant oil applications also help control overwintering fungal spores and can assist with cleaning bark surfaces.
How to Apply Dormant Oil
Dormant oil sprays are typically mixed with water and applied with a hand sprayer, pump sprayer, or hose-end sprayer. Coverage should be thorough but not excessive — the goal is to coat trunks, branches, and bud scales where pests are most likely to overwinter.
Equipment and supplies to consider:
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Dormant Oil Spray — essential for preventative pest control
Sprayers — handheld or pump sprayers make application easier
Protective gear — gloves and eye protection
When spraying, ensure good coverage on both the upper and undersides of branches. Dormant oil works best when temperatures are above freezing but cool (typically between 40–60°F).
Safety and Best Practices
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Apply on dry days with no forecasted rain for at least 24 hours
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Avoid spraying when temperatures exceed 80°F
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Ensure thorough coverage, but do not overapply
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Do not use dormant oil on plants that are actively growing
Dormant oil should not harm beneficial insects at this stage, as most are inactive in winter. However, always read product labels and follow instructions carefully.
Benefits of Dormant Oil Use
Dormant oil sprays can:
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Reduce overwintering scale, mites, aphids, and other pests
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Lower spring pest pressure before pests reproduce
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Improve overall plant health by reducing insect stress
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Decrease reliance on chemical insecticides later in the season
Dormant oil is a simple, effective tool for integrated pest management when used correctly in late winter.
Cover Your Bases Each Season
Dormant oil is one part of a healthy pest management routine for fruit trees and roses. Combining dormant oil applications with good cultural practices such as pruning, sanitation, and proper fertilization sets plants up for success as temperatures warm.
February is a great time to apply Dormant Oil provided you follow these guidelines:
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Apply Dormant Oil to deciduous plants prior to them breaking dormancy.
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Temperatures should range between 40°-70°F and when no frost is predicted for 24 hours.
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Agitate as you spray to keep the solution well-mixed.
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Dormant oil will suffocate overwintering insects, insect eggs, and fungal spores.
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Young insects are more prone to dormant oil as are eggs.
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It is best to get this done in mid to late February or early March.
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Make sure you read the label and use the winter rate.
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If fungal issues were prevalent in the previous season, wait 7-10 days and if you need, apply Copper fungicide.
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Apply Copper prior to bud break. This will protect your fruit trees and roses from having fungal spores enter the terminal buds as they open.
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Copper is also known for helping prevent Fire Blight. Apply prior to warm humid rainy weather a precursor to fire blight. Both dormant oil and copper are organic but not listed as OMRI.
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There are OMRI listed organic oils and fungicides such as Monterey Horticultural Oil, Monterey Garden Insect Spray, and Monterey Fruit Tree Spray Plus. Keep in mind that these are safe. Use with caution to prevent harming beneficial and needed pollinators. On all plant protection products, please read the label and use them accordingly.
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All applications are weather dependent, temperature dependent, and re-application might be necessary but limited due to toxic buildup or negative effects on beneficials.
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Dormant oil applications after leaves have broken should be at the summer rate. During the summer, oil can make plants photosensitive and burn leaves. Please read all directions prior to spraying your plants.
