HYG  Pest newsletter

Issue Index

Past Issues

Dormant Oil

April 14, 1999
Dormant oil sprays for control of insect and mite pests can still be applied to trees that have not broken bud. Many species of trees in northern Illinois are still dormant, but almost all trees in southern Illinois are actively putting out leaves. Spraying trees with dormant oil after bud break will still control these pests, but it may kill the young leaves or cause leaf edges to turn black.

Dormant oil sprays can effectively control such scales as lecanium, cottony maple, euonymous, and obscure; and honeylocust mite can also be controlled with a dormant oil spray. These sprays have little control on oystershell scale, though, and only moderate control on pine needle scale because oystershell scale overwinters primarily as eggs and pine needle scale overwinters partially as eggs.

Apply a dormant oil spray when the temperature will stay above freezing for 24 hours after you spray. Obey label directions. Japanese and sugar maple will be damaged by oil sprays, and oil will take the blue sheen off Colorado blue spruce. (Phil Nixon)

Author: Phil Nixon


College Links