When we look out our windows from our cozy living rooms in winter, we look at a winter landscape that, depending on the weather that particular day, appears to be lifeless.
Nothing could be further from the truth. According to entomologist Hugh Philip, who joined me recently on Garden Talk, the radio show I host in Penticton, a walk through the garden in winter will reveal all kinds of insects in various stages.
Close examination of twigs and bark on trees and shrubs will expose the eggs of many of those insects who share our garden plants with us during the growing season; mites, aphids, scale and leafrollers to name a few.
Others survive the winter quite nicely as larvae, pupae or even adults. I presented a list of well-known garden insects to Hugh and asked him how they manage the snow and cold.
He told our listeners that aphids overwinter as eggs on the new growth of plants, the final generation of several during the growing season. After reproducing as live females throughout the spring and early summer, males are produced as the days get shorter in order to mate with females, who produce eggs. Those eggs are designed not to freeze, and as soon as warm weather arrives along with the flush of new foliage, those eggs will hatch.
Some mite species survive as adult females under bark or bud scales on plants. They move off the leaves where they’ve been living before those leaves fall to the ground. European red mites, however, can be found as tiny masses of red eggs on twigs.
Depending again on the species and whether they produce one or two generations in a year, Hugh explained that leafrollers will overwinter as larvae under bark cracks in special chambers called hibernacula, or as eggs on upper twigs.
Peach tree borer larvae survive at the base of the tree under the bark and emerge as adults in midsummer. They, along with many other larvae, replace part of their blood with glycerol, what we know as anti-freeze. This liquid allows them to survive freezing temperatures throughout the winter. When temperatures warm up the insects begin to produce more blood.
A sudden drop in temperatures in fall, before insects have begun to produce glycerol, might produce a widespread kill but that’s unlikely to happen anytime soon given our changing climate.
The rose leafhopper will lay eggs in the tissue of rose leaves, while the Western leafhopper, which attacks grape foliage, overwinters as an adult on the plant. Hugh explained that a parasite that is found in the egg of the rose leafhopper will attack both species when it emerges in spring. Grape growers are taking advantage of this by planting roses in vineyards.
Many of our most troublesome insects in the vegetable garden can be found in the soil during winter. Tomato hornworms, Colorado potato beetle, wireworms and cutworms all overwinter as either pupae or larvae. Turning over the soil with a shovel in spring and keeping a close eye for these life forms will help eliminate many of them before they hatch out.
Climate change has provided a challenge for entomologists. Warmer winters have produced conditions where insects such as the apple clearwing moth and the corn earworm from southern areas may now be able to survive in a stage. Hugh is always looking for evidence of visitors in the orchard, the field and the garden that may cause future problems for our crops.
The garden may look dormant and lifeless in the coming weeks, but you can be assured that our insect friends are waiting patiently to reacquaint themselves with our flowers and vegetables when spring arrives.