Over-Wintering Bugs The place Are they and What to Do about Them?


Published November 20, 2022 at 8:27 am

Nancy Bliss photo catchy tune

In July, hornworms appeared in large numbers and devoured my tomato plants! When my chard or beans sprout in the spring, earwigs gnaw the new sprouts, as do snails and pill bugs.

Where do they come from, do they appear out of nowhere? All winter long, cold and dark, I rarely see any of these critters, but as soon as it warms up, beware!

Winter can be a tough time for invertebrates (insects and spiders). Cold weather slows them down and makes them easier prey, and the cold can kill. They have devised multiple ways to survive, from burrowing and hibernating to finding warm places to escape to. Preferred wintering spots are piles of leaves, bark or mulch; then they emerge in the spring to do what they do best, helpful or not.

Cleaning up will help prevent many of these insects from finding an easy way into your much warmer home during the winter season. Preventive measures will help reduce the population of undesirables in the coming spring. However, it is not such a simple problem.

Take earwigs, for example (and no, they don’t crawl into your ears). Earwigs are just as useful as pests. They eat aphids, mold and fungus and help with composting. Unlike most insects, female earwigs tend to their eggs until they hatch, even eating mold from the eggs (ugh). But they also like to nibble on tender spring sprouts. Earwigs congregate in large numbers and frankly, they look scary! However, they like to overwinter under piles of leaves, bark, and mulch.

Tomato moths overwinter underground as large, reddish-brown pupae and hatch as sphinx moths in spring. Tilling the garden in late fall as well as early spring helps control populations. However, tillage disrupts helpful soil microorganisms. For this reason I avoid tillage; so a few more hornworms. Mulching around tomato plants in spring is helpful in preventing moths from emerging. Crop rotation is another good preventive measure.

Cabbage whites produce small green worms that devour everything in the cabbage family. These hibernate as pupae on plant stems – a good reason to clean up dead vegetation.

Other interesting wintering invertebrates include praying mantises and ladybugs, both beneficial insects. Praying mantises lay their eggs (up to 400 eggs) in a pouch usually attached to a plant stem. The sac hardens into a tough brown shell that hatches in spring. Ladybugs gather together and snuggle up with hundreds or thousands of other bugs to protect themselves from the weather and frost. You can find places in cracks, crevices, tree bark and even your house or roof to spend the winter. In the spring they appear en masse, a great sight to behold.

Preventative measures include removing mulch, leaves, and bark, especially around your home’s foundation. Winterize by sealing door jambs and window frames; Install shielding over ventilation access points; Install door sweeps and thresholds. Maybe order gardens for those who dig in! But let’s appreciate the diversity and complexity of these creatures, both invading and protecting. Practice a little live and let live. (Well, maybe not for roaches!)

Nancy Bliss is a master gardener at the University of California Cooperative Extension in Tuolumne County.

If you have questions about the garden, call the University of California Master Gardeners Hotline at (209) 533-5912 in Tuolumne County, 209-754-2880 in Calaveras County, or email us at mgtuolumne@ucdavis .edu. From rainwater tanks to drought-resistant plants, we can help you find an answer.

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