Late fall best time to start treating fruit trees for pests

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Last Updated: 
December 6, 2005

CORVALLIS - To avoid some of the pests and diseases that can harm your fruit trees before the next growing season, late fall is the best time clean up the area where your fruit trees grow.

Dropped fruit, dead branches and leaves around your fruit trees should be picked up now. This gets rid of lots of the larvae, cocoons, and eggs that winter-over in plant debris and soil.

The dormant season, November through March, is also the optimal time to control pests taking up residence in the cracks and crevices of fruit trees. Late fall is the best time for the first treatment. Treating fruit trees during the cool time of year catches pests at a vulnerable and inactive time in their life cycles.

"Early preventative care is much more effective than waiting until the weather warms up and pests become active in spring and summer," explained Ross Penhallegon, horticulturist with the Oregon State University Extension Service.

Below are some tried and true treatments for fruit trees in Oregon, along with their proper timing. These treatments are widely available at garden centers or discount home stores. Always follow label directions, and apply either early on still mornings or late evenings to avoid wind drift.

  • Dormant oil: Apply when trees are dormant, November through March, after all the leaves have fallen. It is best applied just before bud break in the spring. Mix with water as directed and spray to all surfaces of the trunk, branches and twigs. Apply when the temperature is expected to rise during the day; temperatures below 35 degrees can damage the bark. Dormant oil controls aphids, scale, spider mites, and many other insects by desiccating or smothering eggs and larvae.
  • Lime-Sulfur: Controls fungal and bacterial diseases such as fire blight, scab, bacterial blights and anthracnose. Peach leaf curl is a good example of fungal disease. Spray three times during the dormant seasons, usually December through February.
  • Fixed Copper: Controls canker on cherries, peaches and plums. Canker is a disease that in extreme cases can kill a tree. Allow two weeks between applications of copper and any sprays containing sulfur. Add a spreader-sticker product to help copper adhere to the tree surface.
  • Exterior-grade white latex paint: Once autumn leaves drop off, direct sunlight hits tree trunks and sometimes cracks the bark of younger trees. Cracked bark provides habitat for pests and may allow severe cold to further damage the tree. To protect the exposed bark of younger trees from cracking, coat the trunks with exterior grade white latex paint diluted 1-to-1 with water. White reflects the sunlight and provides a sunscreen for the bark.
    Additional fruit tree chores to put on your late fall through late winter calendar:
  • Apples: Apply copper before fall rains; dormant oil once or twice from January through March; lime-sulfur in early spring (just before buds open) and wettable sulfur just after petal fall.
  • Apricots: Apply copper before the fall rains. Apply dormant oil January through February. Do not apply sprays containing sulfur to apricots or you could damage them. Be aware that apricots are difficult to raise in the Willamette Valley.
  • Cherries: Use wettable sulfur or lime-sulfur applied weekly during blooming for brown rot. Information on synthetic sprays to control cherry fruit fly is available from your local county office of the OSU Extension Service.
  • Pears: Use copper before the fall rains. Apply dormant oil three times beginning in fall (Oct./Nov.), again during winter (Dec./Feb.), and finally in March just before buds open. Spray lime-sulfur in early spring before buds open and wettable sulfur just after petal fall.
  • Peaches: Spray copper or a good dormant fungicide three to four times between December and bud break. Spray copper or lime sulfur before fall rains and again in the spring just before bud break. Apply sulfur weekly during blooming and again after all petals have fallen.
Author: Carol Savonen