White Prunicola Scale on Cherry Tree

White Prunicola Scale on Cherry Tree

The time for an initial dormant horticultural oil treatment this spring is almost upon us. This ttreatment is extremely effective in reducing populations of many tree damaging insects on Long Island, including spider mites, various scale insects (both hard and soft), adelgids, aphids, mealybugs and other insects. Treatment is made by spraying deciduous and evergreen ornamentals with a 2% mixture of refined horticultural oil ( a reduced-risk insecticide, often mistakenly called “organic”) which suffocates overwintered insects as they emerge in nymph and immature stages. As far back as the late 1800’s farmers used a mixture of kerosene and soap to prevent pest outbreaks. Unfortunately, this treatment was highly phytotoxic and caused damage to the plants, so refined oils were developed for the same purpose. Dormant oil treatments have been used for decades by farmers to control agricultural insects and have been a part of effective tree spraying programs for many, many years. They are considered an essential part of any organic pest control program, mainly because there is no residual effect and no accumulation in the environment. With today’s highly refined, broad range oils, treatments can be made during the active growing season as well without harm to foliage.

We usually schedule our dormant oil sprays to begin the last week of March through mid-April. This is the period when Growing Degree Days (GDD) have begun to accumulate beyond a threshold of 7, when the treatment becomes effective in killing emerging pests. Most of the insects we go after need to have treatments begin in the 7 to 35 GDD range. If we experience a late spring and the GDD hasn’t begun to rise, we delay treatments until they become effective.

If you are interested in an organic pest program for your property, or just need one of our arborists to stop by and give you advice, please call us right away at (631) 698-2929 or e-mail us at info@foxtreeservice.com