Gardening-Organic Pest Control

This March 22, 2014 photo shows a ladybug on a residential property in Langley, Wash. Many gardeners use pesticides — organic or otherwise — only as a last resort. They opt instead for such predatory insects as ladybugs, which individually can consume up to 5,000 aphids during their lifetime, and can be bought commercially and released from containers into the garden. (AP Photo/Dean Fosdick)

While we’re busy pulling on wool socks and long underwear, the insects and other creepy-crawlies in our yards are utilizing an amazing array of mechanisms to withstand wintry weather.

We tend to classify insects as either beneficial or pests, but they’ve all figured out ways to survive, including migration, overwintering and hibernation. Understanding how certain bugs spend the winter can help us take action to reduce problem pests for the next growing season.

Some insects can fly long distances to find warmer climates. One of the best known examples is the monarch butterfly, which cannot survive cold winters in the United States and migrate up to 2,500 miles to avoid them.

Other insects brave the cold and stay in place, using many interesting mechanisms and making use of materials in our gardens. Heavy leaf litter acts as insulation and shelter for many species, and is a common way for eggs, larvae or pupae to survive low temperatures. Some grubs and worms simply burrow deeper into the soil to escape the cold. Some convert part of the water in their bodies to glycerol, which acts as antifreeze. At certain life stages, some insects live and survive in water. Examples include the nymphs of dragonflies, mayflies and stoneflies. They can survive in ponds and streams beneath a layer of ice, actively feeding and growing all winter before emerging as adults in the early spring.

Another mechanism for overwintering is a mutually beneficial relationship between species. Some species of ants feed heavily on the sweet, sticky honeydew excretion aphids leave on plants. Ants have developed several strategies to secure this food source. One is to act as bodyguards to protect aphids from predator insects that would eat them. Another is to act as shepherds, carrying the aphid eggs into their nest where it is warm enough for the eggs to survive the winter. The ants watch over and protect the eggs all winter, then move them in the spring onto new, tender, leaf foliage where the eggs hatch and immediately begin eating.

Hibernation is less common, but some adult insects will make use of tree holes, firewood piles, brush piles, leaf litter or spaces under logs and rocks. Some even shelter under the eaves of houses and shed or inside attic spaces. Others build their own shelter. Honeybees are a great example. They build hives and stock up on honey as a winter food source. As the honey oxidizes, it releases heat to help keep the hive warm. Worker bees circulate heat by fanning their wings. A hive of honeybees can eat up to 30 pounds of honey during the winter. It is this food and shelter that allows them to survive the cold winter weather.

Understanding where bugs seek winter shelter helps us reduce populations of problem pests. Cleaning up the garden in the fall, rather than waiting for spring can reduce many eggs, larvae and adult pests. Removing dead plants, rotting fruit, leaf litter, weeds, brush piles, decaying trees, etc., in the fall will reduce winter shelter.

Prune back roses in late fall to remove most of the leaf canopy where aphids overwinter, and then do a final pruning in the spring. This will go a long way toward reducing aphid problems that are so common in roses.

In general, insects are better able to survive cold weather more easily when the temperatures are stable, rather than the fluctuations of freeze-thaw cycles. In vegetable gardens and annual beds, rake, till or turn the soil to a depth of 3-4 inches several times during the winter, especially after a hard freeze-thaw cycle. That will expose pest larvae to the killing winter elements. It also exposes them to hungry birds who will welcome a high protein meal and will pick your garden clean of pests.

The vast majority of insects are not problem pests and should be welcomed into our gardens as part of a healthy ecosystem. However, if you had a serious problem with aphids, squash bugs, tomato hornworms, cabbage worms, potato beetles, (to name just a few) cleaning up the garden in the fall, rather than waiting until spring, will go a long way in reducing pest problems in your garden next year.

WSU Extension Master Gardener Program is an organization of trained volunteers dedicated to horticulture and community service. The Master Gardener Walk-In Diagnostic Clinic operates from 9 a.m. to noon and 1-4 p.m. Mondays, Wednesdays and Fridays. Direct questions about gardening, landscaping or this program to the Master Gardener Clinic at 509-574-1604, or leave samples for identification at the WSU Extension office. Leave a message with your name, phone number, email address and the nature of your problem or question. You can also email your questions to gardener@co.yakima.wa.us and include pictures if you have them. A member of the Master Gardener Clinic team will check voicemails and emails, and reply as soon as possible. The WSU Extension office is at 2403 S. 18th St., Suite 100, in Union Gap. Call 509-574-1600. New volunteers are welcome.