Do you ever wonder where all the insects that inhabit our gardens from the spring through the fall go once winter arrives? Insects have developed a number of overwintering strategies. Some fly south to warmer climes. Others have found ways to hibernate, while others go underground. Some lay eggs that will hatch once spring temperatures warm.
Knowing where and in what stage in their life cycle insects spend the winter is not only interesting, but also helpful for managing both beneficial and harmful types in your garden.
Like many humans, some species of butterflies, moths, dragonflies, beetles, grasshoppers and true bugs migrate to escape the winter cold. A Texas entomologist, Mike Quinn, estimates that at least 71 species of insects migrate. The most well-known migrating insect is the Monarch butterfly.
Not all butterflies and moths are migratory, however. Some survive the winter “hibernating.” The pupae of most butterflies (chrysalises) or moths (cocoons) can be found attached to an above-ground object, such as a branch. Know which of these pollinators you want to inhabit your garden and learn what their pupae look like and where their pupae might be spending the winter so that you don’t accidentally destroy them.
Not all butterflies and moths are beneficial in our gardens and orchards. One example is the codling moth. After eating the core and seeds of the apple, larvae form silken cocoons under loose bark, in soil, or in debris around the base of a tree, where they stay until they emerge in spring. To reduce their population, find a picture of these cocoons and check for them, destroying any you find.
Bee species have developed differing hibernating strategies for surviving winter. With bumblebees, most of the colony dies before winter, leaving the queen to hibernate on her own in soil banks such as abandoned rodent holes. Honey bee workers and their queen hibernate in their hives or nests clustered tightly together for warmth. Adult solitary bees, such as mason and carpenter bees, have short lifespans so it is their eggs and larvae that overwinter. The female lays her eggs in a nest and then seals it with pollen and nectar for when the eggs hatch. Leave these nests alone if you see them and you will be rewarded with them pollinating your plants during the growing seasons.
In plant diagnosis clinic, we get calls from people who are unhappy with insects that have chosen their houses to hibernate. Box elder bugs, seed bugs, elm leaf beetles, the non-native invasive Asian lady beetle and one of our newer pests, the brown marmorated stink bug, are examples. You can vacuum them up when you find them.
Some insects overwinter in the soil underground, either as adults, larvae or eggs. Root weevil larvae overwinter in soil around roots, emerging as adults in the spring. Cultivating the soil in April or May before planting can eliminate overwintering larvae. Although not an insect, slugs are pests in our gardens. Adults and the eggs spend the winter in the topsoil or under garden debris, mulch, or boards on the ground. Controlling slugs is one reason that it’s important to remove dead plants in your garden.
As I have learned, insect winter survival strategies are diverse and knowing their habits helps me to better manage them in my garden.
A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Casey Leigh is one of four columnists featured. To learn more, visit wwrld.us/cdmg or call 667-6540.