Dormant Oil Application

By Wendy Kjeldbjerg,

  Filed under: Seasonal Plant Care
  Comments: None


One of the best and safest methods to control mite and scale insects that damage trees is with the use of horticulture (dormant) oils. Horticultural oils are very effective for controlling soft-bodied insects and over-wintering egg masses before the insects damage your applicable plants. Scale insects, mites, gall forming insects, cankerworms, mealy bugs, and other damaging insects are controlled through membrane disruption and/or suffocation. The oil is sprayed on the branches of the dormant tree or bush and it soaks into the shell of the insect blocking their oxygen. This highly refined oil is applied during the dormant season which helps to avoid non-targeted insects, which makes this spray an environmentally friendly alternative. Certain tree species are sensitive to the oil and are not sprayed. Preventive dor­mant oil applications can save time and money by reducing the amount of applications necessary to control those types of insects once they are active.








When is the best best time to apply dormant oil? The service is very weather-dependent. The daily temperature is at least 40 degrees F. and will stay that way for at least 24 hours. The oil should be applied early enough in the spring before the buds on the trees have begun to swell. Trees that would benefit from a dormant oil application are apples, crabapples, plums, quince and pears, among others.

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