University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

How Yard and Garden Pests Overwinter

November 23, 2000

As fall fades into winter, yards and gardens have been cleaned up and plants have gone dormant. What about the insect pests of the growing season? Most are protected and will be ready to reappear next season as conditions again become favorable.

Many common insect pests of the vegetable garden actually overwinter in plant debris left in the garden, so it does pay to clean up the garden at the end of the season. For example, the cabbageworms (imported & looper) that may have infested your cabbage or broccoli last summer are now overwintering in the pupa stage in plant debris. Cucumber beetles, a threat to cucumbers and other vine crops, overwinter as adult beetles in debris, waiting for spring to return and fresh plants to appear. Tomato hornworm, the big green "worms" on the tomato plants, also spends winter as pupa in plant debris.

Many nuisance insects and insect relatives overwinter in sheltered areas and debris, such as under the siding of your house or in a pile of firewood. These include boxelder bugs, centipedes, earwigs, and millipedes. The Asian multicolored ladybug, which was so common back in October, is now most likely resting under siding or perhaps someplace inside the home. These types of insects may become active during warm spells of the winter months.
White grubs can be big problems on lawns in late summer and early fall. Right now, they are safely resting as a larva (grub) in the soil below the frostline. The adult beetle will emerge late next spring to start the cycle over again.

You don't readily see them, but some caterpillars overwinter on the host tree. For example, conspicuous "tents" of early spring signal Eastern tent caterpillars are again present and feeding on leaves of trees. But since early July the Eastern tent caterpillar has been an egg case on the twig of host tree, often a crabapple. The egg case will stay there all winter, with caterpillars hatching out and feeding as the trees leaf out again in spring. Gypsy moths also overwinter as a buff-colored "furry" egg case on the trunks and limbs of trees.

Finally, most of the insect borers that attack trees spend winter as a larva in trunk of host tree. They emerge in late spring or early summer as adult moths or beetles, which then lay more eggs to start the cycle over again. Once under the bark, there is no way to control this pest.


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