Thorough coverage of all plant parts is essential when applying dormant oil sprays to kill over-wintering insects on fruit trees and ornamentals. Dormant oils kill insects and their eggs by coating them with the oil so that they smother. Even eggs must breathe by exchanging gases through their shells, and a coating of oil interferes with this process and kills the egg. You need to pay particular attention to the undersides of the limbs and leaves as well as all cracks, crevices, and deep joints in the bark. Spray the plant from different angles so you get thorough coverage.
Tent caterpillar eggs are just one of the many kinds of insect eggs living on plants during the winter. The egg stage is the most common over-wintering form because it is fairly resistant to cold temperatures.
Joan Blackstone, Smith County Master Gardener
Texas Cooperative Extension
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