January 9, 2009

Cold temperatures cause insect populations to decline, but many insects can survive in trees or crop residues left in fields or gardens during the winter. By practicing pest management now, producers can lessen the number of insects overwintering, and thus lower the number of insects that reemerge during the next growing season, said Ric Bessin, extension entomologist with the University of Kentucky College of Agriculture.

When producers harvest their vegetable crops, oftentimes plants and vegetables that are undesirable or not fully developed are left on the ground. These residues are attractive food sources and shelters for numerous insect pests including corn earworm, squash vine borer and squash bug.

In order to survive the winter, insects need to reach a certain stage of development. Crop residues left on the ground allow them to complete their development.

Bessin said despite the size of a farming operation, removing the residue hinders insect growth and survival. For producers of large operations, plowing or disking fields is a great way to rid the surface of residue and provide some organic matter to the soil. Home gardeners can remove residue from their beds and compost it.

            In addition to overwintering in crop residues, some insects and mites can survive through the winter in egg and nymph stages in fruit and ornamental trees. Horticultural or dormant oils can kill many of these insects.

"It is less disruptive to control pests during the winter with oils than in the summer with other pesticides," he said.

Producers who use oils should carefully read labels and exactly follow directions. Different kinds of oils are used in different situations.

"While dormant oils are normally safe, they can be over applied, which could cause damage to the trees," Bessin said.

Oils should be tested on a small number of plants or a section of a tree limb before they are applied to an entire field or orchard. Any negative effects will appear within a few days.

            Timing is also important to killing some insects, including the San Jose scale. To prevent reemergence of this insect, producers should apply oils during January and February. Oils that protect against other pests, including the European red mite and the rosy apple aphid, should not be applied until after bud break.

            Oils are available at most places that sell gardening supplies.

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