Dormant Oil Spray for Fruit Trees: When to Spray and How to Mix It

Spray horticultural (dormant) oil on fruit trees in late winter while they are still dormant, up to about the green tip stage when buds first show color, on a calm, dry day when temperatures stay above about 40°F with no freeze expected for 24 to 48 hours. The oil smothers overwintering scale insects, mite eggs, and aphid eggs on bark and twigs. Mix it at the dormant rate on the label, and coat every branch until it just starts to drip.

What dormant oil does

Horticultural oils are highly refined petroleum or plant oils mixed with an emulsifier so they blend with water. A thin film covers small insects and eggs and blocks their breathing. It works on contact only, leaves little residue, and has a low impact on beneficial insects that are not present on the bark in late winter. It is a cornerstone of home orchard pest control on apples, pears, plums, peaches, and cherries.

Timing

• Dormant window: late winter, after the coldest weather and before buds swell.
• Delayed dormant window: from bud swell through green tip, when buds show a hint of green. Many pests are more exposed then, and this is often the most effective timing.
• Stop at bloom. Do not spray oil on open blossoms.
• Weather: choose a calm, dry day, ideally 50 to 70°F, with temperatures staying above about 40°F for at least a day afterward. Oil on bark that freezes can injure buds, and rain within a few hours washes it off.

Use the late fall and early winter months to get ready: rake up and remove fallen fruit and dried mummies from branches, which harbor disease, and plan late winter pruning. See our guides to folding pruning saws and bypass pruning shears. Prune first, then spray, so you are not coating wood you plan to remove.

Mixing and spraying

1. Read the label rate. Dormant rates for most concentrates run about 2 to 4 percent, which is higher than summer rates. Follow your product exactly.
2. Fill the sprayer half full with water, add the oil, then top up and shake well. Oil separates, so agitate the tank every few minutes while spraying.
3. Cover everything: trunk, scaffold limbs, twigs, and bud clusters, including undersides. Scale hides in bark crevices, so full coverage matters more than a heavy coat.
4. Spray until the bark looks wet and just begins to drip, then move on.
5. Rinse the sprayer with clean water when you finish, spraying some through the wand and nozzle.

When not to use oil

• Within 30 days before or after a sulfur spray, and never mixed with sulfur in the tank. The combination burns foliage and buds.
• On trees that are drought stressed. Water deeply a day or two before spraying in dry winters.
• On sensitive plants nearby. Japanese maples, some evergreens, and blue spruce can be damaged, and oil removes the blue cast from blue conifers. Shield them or spray on a still day.

Safety

Wear splash goggles, chemical-resistant gloves, long sleeves, and closed shoes while mixing and spraying. Mix outside, keep children and pets away until the spray dries, and never spray on windy days. Store concentrate in its original container, locked away. Read the full label before use, since it is the legal guide for the product.

Bottom line

Mark late winter on your calendar: prune, then spray dormant oil at the label rate on a calm day above 40°F, from late dormancy through green tip, coating every branch to the drip point. Keep sulfur at least 30 days away. For planting more trees, our guide to fruit trees to plant in fall covers choices and spacing, and young trunks still need tree wrap and guards over winter.

Related reading

• Raspberry canes to plant in fall
• Cleaning and sharpening garden tools before winter

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