Use prevention methods to fight fruit tree diseases

By Kym Pokorny

Face next season’s fruit tree disease and pest problems by making a preventative strategy now.

Since late winter is a good time to plant bareroot trees, the first line of defense is to choose a resistant variety. Otherwise, look to sanitation and low-toxicity sprays such as dormant oil and copper to keep trees healthy.

First up, be vigilant about removing dropped fruit and leaves that might be harboring pests. Follow that with appropriate sprays to get at those pesky insects, fungi and bacteria that like to make a home in cracks and crevices, said Ross Penhallegon, horticulturist with the Oregon State University Extension Service. Spraying in late fall to early spring is more effective than waiting until the weather warms up and pests become active.

Below are Penhallegon’s recommendations for the least toxic sprays and treatments for fruit trees. These products are usually available at garden centers. Always follow label directions. For more information, contact your local Extension office or submit a question to Extension’s Ask an Expert online helpdesk http://extension.oregonstate.edu/extension-ask-an-expert. ; For a more expanded look on subject, check out Extension’s publication Growing Tree Fruit and Nuts in the Home Orchard http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/13718/EC%20819.pdf. />

Dormant Oil: Mix with water as directed and spray on all surfaces of the trunk, branches and twigs. The best time to control mites, aphids and scale is early to mid-March, just before the tree begins to emerge from dormancy. 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: Spray to control fungal and bacterial diseases such as peach leaf curl, pseudomonas and scab. It’s very important not to apply sulfur sprays to apricots.

Fixed Copper: Spray on apples, pears, cherries, peaches and plums to control canker. 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.

Latex paint: Coat the trunks of young trees with white exterior latex paint mixed half-and-half with water. The paint reflects strong sunlight and prevents sunburn and winter burn that can cause tissue damage and lead to cracks, a favorite place for pests to overwinter and cause substantial winter damage.

Here are some tips from Penhallegon for specific fruit trees:

Apples: Spray copper as the leaves are falling; dormant oil once or twice from February through March; copper in January or February (just before buds open) and wettable sulfur just after petal fall.

Apricots: Spray copper before the fall rains; dormant oil in February.

Cherries: Use wettable sulfur or lime-sulfur applied weekly during blooming for brown rot.

Pears: Spray copper before the fall rains. Apply lime-sulfur two to three times between early December and March beginning in fall, again during winter, and finally just before buds open in March. Use dormant oil 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, usually once a month starting December 15 and ending March 15. Spray fungicides during break in fall rains and in early spring just before bud break.

Image above: Photo by Keith Weller/USDA. Prevention is the best medicine for fighting diseases on pears and other fruit trees.

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