Some over-wintering insects can be killed with dormant oil

I?m glad you haven?t forgotten the dormant oil, but it is now time to Get?r Done!

Dormant oil will suffocate insects that can?t crawl out of it. Absolute total coverage is essential for effective control. Insects not covered will not be killed. The oil must cover the insects or their eggs that are overwintering within the crevices of the bark, etc. The oil also melts away the waxy covering of scale insects and allows them to dry out.

It is usually best sprayed January through March. Some labels advise one or two applications, depending on the pest population. Always follow label directions. Avoid spraying blue spruce, due to losing the color for one year.

Dormant oil can be applied in the landscape or commercial nursery as it is in commercial orchards. Nursery producers might should apply dormant oil Dec-Jan before they get too involved with digging and shipping.

Dormant oil will kill: immature whiteflies; the white cottony pine bark adelgid (check the trunk and branches of white pine); spider mites, rust mites, and eriophyid mites on (hemlock, juniper, spruce, arborvitae, and occasionally burning bush); broad mites on red maple cultivars, etc., first year in field; scale on (Manhattan euonymus, burning bush, mulberry, ash, lilac, dec. magnolias, etc.); some types of overwintering eggs (the spiny witch hazel leaf gall aphid on birch and the white pine aphid); oak phylloxera (that causes oak leaves to wad up in July).

Label directions usually suggest that the temperature should be between 40-85 degrees during the application and it should not freeze within 24 to 48 hours of the application. Recent research suggests freezing that night of no concern.

There must be adequate pressure to blow the oil through the plants, achieving total coverage. Air blast sprayers are great for achieving coverage, but the gallons per acre may have to be increased to obtain control. (50 to 100 gallons depending on plant density)

This is a very environmentally safe and very effective product. Insects do not develop a resistance to being suffocated. A light rain will not remove it.

Dormant oils are relatively safe to people. These oils are essentially the same as baby oil or mineral oil sold in drug stores except for the addition of emulsifiers. Be careful not to breathe the spray mist as serious pulmonary problems may result.

Ensure that the plants have received sufficient cold temperatures and are completely dormant. Avoid spraying plants under water stress or with tender new growth.

Oil and water separate rapidly. Constant agitation is required. If a sprayer has been idle for a few minutes, be sure to spray into the tank for a minute to ensure that the oil is thoroughly mixed or begin spraying several feet from the crop. Otherwise, the emulsion in the hose and tips will have separated and the first plants sprayed may receive pure water or pure oil. The oil will burn.