Using Dormant Oil

Using Volk or dormant Oil or Heavy Horticulture Oil
Dormant oil sprays are designed to be used in the early winter through early spring to smother overwintering scales and the eggs of insects such as aphids and mites. The heavy oils must only be used when trees are leafless, because they will damage foliage. Spray when the weather forecast indicates no rain or freezing night temperatures for at least 48 hours. The daytime temperatures should range from at least 40øF to 80øF.
Late winter, before any leaf buds begin to open, is the best time to spray dormant oil on fruit trees to control a host of sucking and chewing insects like aphids, thrips, mealybugs, whitefly, pear psylla and various forms of scale and red spider mites. The oil also destroys the eggs of codling moths, Oriental fruit moths and assorted leaf rollers and cankerworms.
These dormant oil sprays can harm certain trees and shrubs, including beech, maple, hickory, mountain ash, red and black oak, walnut, butternut, yew, azaleas, and broad-leaved evergreens. In most of these cases, you can use the newer horticultural oils, which are lighter.

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