Treat fruit tree pests while they are still dormant

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Last Updated: 
December 29, 2005

CORVALLIS - Treating for fruit tree pests in the cool, dormant months is much more effective than waiting until the weather warms up and pests become active in spring and summer. It's much harder to control pests during their warm, active months, as their populations can grow quickly.

Spraying fruit trees during the cool late winter/early spring dormant season catches pests at a vulnerable and inactive time in their life cycles, explained Ross Penhallegon, horticulturist with the Oregon State University Extension Service.

Before considering spraying, clean up all the refuse around your fruit trees to get rid of larvae, cocoons, and eggs that winter-over in plant debris.

Then, it is time to spray, especially if you want to control pests residing in the cracks and crevices of fruit trees. Although a first spraying is usually called for in late fall, it's not too late to set up a schedule that will reduce bug bevies big time.

Following is a list of tried and true sprays for fruit trees, along with the timing for a few favorite fruits. These products are widely available at garden centers. Always follow label directions, and spray on still days to avoid wind drift. Call or visit your local county office of the OSU Extension Service for a spray schedule appropriate for your area.

Dormant oil should be applied when trees are dormant, after all the leaves have fallen. 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; falling temperatures can force oil into the bark and cause damage. Dormant oil controls aphids, scale, spider mites, and many other insects by desiccating or smothering eggs and larvae.

Lime-sulfur can be sprayed to control fungal and bacterial diseases such as fire blight and anthracnose. Peach leaf curl is a good example of fungal disease. This is typically done between Dec. 15 and Jan. 15.

Fixed copper can be sprayed on cherries, peaches, and plums to control canker, which in extreme cases can kill a tree. Allow six weeks between applications of copper and any sprays containing sulfur. Add a spreader-sticker product to help copper adhere to the tree surface.

Paint can be used to coat the trunks of young trees with white latex paint that's mixed half and half with water. It reflects strong sunlight that, once the leaves fall, can cause cracking, a favorite place for pests to overwinter.

Here's some timing to put on your calendar. It is too late for the fall treatments, but there's still time for most of the recommended winter and spring treatments.

Apples: Apply copper before fall rains (too late this year); dormant oil once or twice from December through February; lime-sulfur in early spring (just before buds open) and wettable sulfur just after petal fall.

Apricots: Copper before the fall rains; dormant oil December through February. Do NOT apply sprays containing sulfur to apricots or you could damage them.

Cherries: Use wettable sulfur or other appropriate fungicide 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; 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 again with wettable sulfur or other appropriate fungicide just after petal fall.

Peaches: Spray copper before fall rains and in spring just before bud break; lime-sulfur October to November; two sprays of dormant oil December to February; sulfur weekly during blooming and again after all petals have fallen.

For questions about appropriate fungicides contact a horticulturist or Master Gardener help desk at your local county office of the OSU Extension office.

Author: Carol Savonen