CORVALLIS, Ore. — As winter settles in, it’s the right time to give fruit trees the care they need for spring.
Applying dormant sprays — horticultural oil, copper and sulfur — now will help keep common insects and diseases in check, said Ashley Thompson, Oregon State University Extension Service fruit tree specialist and assistant professor in the College of Agricultural Sciences.
Dormant sprays target pests such as mites, aphids, leafhoppers, mealybugs and codling moth, and diseases such as apple and pear scab, peach leaf curl, bacterial blight and fire blight.
“You want to use products that have low toxicity, and won’t cause a lot of problems for the environment. Dormant sprays score pretty well.”
Superior or horticultural oil is a highly refined oil that, when mixed with water and sprayed on trees, smothers overwintering insects and eggs. Sulfur is a fungicide that controls fungal diseases such as apple scab. Copper is a fungicide and bactericide that controls diseases including bacterial blight, fire blight and Nectria canker. Rotating copper and sulfur allows copper to act on bacteria while sulfur targets fungal diseases.
“They are a really important part of good IPM,” Thompson said. “When you’re planning a program, you want to use products that have low toxicity, and won’t cause a lot of problems for the environment. Dormant sprays score pretty well. Their toxicity level for animals is pretty low if you follow the labels. Horticultural oil kills target insects, but beneficial insects are rarely around trees in the dormant season.”
Three-spray winter schedule
A reliable schedule Thompson recommends is:
- Around Thanksgiving, apply copper to knock back bacteria and fungal spores.
- In early January, spray sulfur, then at least two weeks later spray horticultural oil so it can reach overwintering insects.
- In mid- to late February, apply a second copper spray before buds begin to open.
Do not mix copper and sulfur in the same tank, and do not mix sulfur and oil. If the first spray was missed, the January application is the most important, and it is still worthwhile to make the final spray.
A good reference for product choices and timing is Extension’s Managing Diseases and Insects in Home Orchards.
Ashley Thompson’s winter fruit tree tips
- Read and follow all pesticide labels. Using products incorrectly can harm people, the environment and the tree.
- Spray when temperatures are above freezing and before buds break.
- Apply horticultural oil only during dormancy for the best coverage.
- Prune in January so late winter sprays also cover pruning wounds.
- Do not mix copper and sulfur in the same sprayer.
- Clean up fruit, leaves, weeds and debris under trees where codling moth and other insects overwinter. If raking isn’t realistic, mow leaves several times to speed decomposition.
- Prune out diseased wood.
- Add organic matter around trees for fertility, but keep mulch away from the trunk.
- Accept a little fruit damage rather than relying on higher-toxicity products.
- Consider dwarf trees so spraying can be done safely from the ground.
For more information on growing and maintaining backyard fruit trees, consult Extension’s Growing tree fruits and nuts at home and Training and pruning your home orchard.
Previously titled Get a leg up on fruit tree problems with dormant oils
Use pesticides safely!
- Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
- Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
- Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.
