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Cornell University : Cornell Cooperative Extension
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Using Horticulture and Dormant Oils |
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Horticulture oil has gained wide acceptance in recent years in managing pests. Oil is safe to plants and the environment while being effective in controlling many types of insect and mite pests. Horticultural oil is also a relatively safe material for the applicator. For oil to be effective, the material must coat the pest or egg completely for optimum results. Read the label to become familiar with all the precautions and application information. Some oils should not be used in combination with a spray containing certain chemicals. Phytotoxicity, the burning of leaves, is possible with a few sensitive species when applied under high temperatures. Phytotoxic symptoms may appear as twig dieback, leaf burn, and killing of new growth. Oil also removes the blue coloration from plants such as Blue Spruce and Blue Juniper. Several grades of horticulture oil are available. Some are strictly limited to dormant use while others can be safely applied to actively growing plants in spring and summer. Dormant application is timed for late winter and early spring when plants are dormant. This preventive application is effective against the overwintering stages of pests such as scales, adelgids, and mites. Oils should not be applied to plants when there is a danger of freezing. Horticulture oil, or summer oil, applied during spring and summer is safe on many plants when used properly. Plants should not be under moisture stress or phytotoxicity may result. Up to four treatments per season can be applied safely. Cornell
Cooperative Extension Yates Association |
