EUGENE – Prevention is the first step in controlling diseases and insect pests in home orchards. Many problems can be avoided by choosing resistant fruit tree varieties and providing them with proper care. That care includes removing all dropped fruit and leaves that might be harboring pests.
But even the most vigilant gardeners may need to spray their trees during the dormant season to reduce over-wintering pest and disease organisms.
Spraying fruit trees during the cool seasons, November through March, can help control pests that take up residence in the cracks and crevices, according to Ross Penhallegon, horticulturist with the Oregon State University Extension Service. Such dormant spraying is more effective than waiting until the weather warms and pests become active.
Below are some least toxic sprays and treatments for fruit trees. These products are widely available at garden centers. Always follow label directions.
Dormant Oil: Apply when trees are dormant, November through March, 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; 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, fire blight, scab and anthracnose. Do NOT 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 latex paint mixed half-and-half with water. The paint reflects strong sunlight that, once the leaves fall, can cause cracking, a favorite place for pests to overwinter and can cause substantial winter damage.
Here are some tips for specific fruit trees:
Apples: Spray copper before fall rains; dormant oil once or twice from January through March; lime-sulfur in January or February (just before buds open) and wettable sulfur just after petal fall.
Apricots: Spray copper before the fall rains and dormant oil in February.
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 at your local county office of the OSU Extension Service.
Pears: Spray copper before the fall rains; spray lime-sulfur two to three times beginning in fall, again during winter, and finally in March just before buds open; spray 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. Spray copper or lime-sulfur before fall rains and in spring just before bud break; apply sulfur weekly during blooming and again after all petals have fallen.