By Lisa Mason
Colorado’s winter has been record-breaking in terms of lack of moisture and warm temperatures. While that might seem beneficial to insects’ survival, a lack of snow cover and early emergence from dormancy .
Strategies for insects surviving winter
Insects overwinter in various life stages, and have adapted to survive cold and snowy winters. Populations ebb and flow from year to year based on a variety of variables, including food/host plant availability, weather patterns and habitat.
Adult insects that will be active on warm winter days include boxelder bugs, elm seed bugs, elm leaf beetles, stink bugs, Western conifer seed bugs, some flies and lady beetles. Sometimes they can be a nuisance — like conifer seed bugs that might wander into your home to find a place to keep warm — but generally these insects are harmless. Boxelder bugs can often appear in high numbers on the south side of a building.
Some species will migrate to sheltered spaces, such as in plant debris or bark crevices. Of note, the convergent lady beetle will migrate to higher elevations and spend the winter in sheltered areas in mass aggregations with other lady beetles.
Some insects will spend the cold temperatures in a hibernation-like state called diapause. This phenomenon is common among insects and arthropods of various life stages, in which they cannot continue development until the temperatures and conditions are more favorable due to antifreeze-like chemicals in their bodies. A common example is the woolly bear caterpillar, which overwinters by hibernating in leaf litter. When summer arrives, they complete metamorphosis and transform to an adult Isabella tiger moth.
Insects that overwinter as eggs include grasshoppers, aphids, mantids, some species of butterflies and moths like the Colorado hairstreak. Some will overwinter as a pupa stage (swallowtail butterflies, and some beetle species), and others as larva or nymphs (ground-nesting bees and wasps, some species of beetles, grasshoppers, moths and butterflies). Some species rely on underground or sheltered protection in the environment during different life stages.
Why am I seeing so many honey bees?
Honey bees are often seen outside the hive on warm winter days. Anytime temperatures rise above 55 degrees, honey bees may take a cleansing flight, which provides them the opportunity to relieve themselves. Honey bees may also forage for whatever they can find, including tiny bits of protein at bird feeders. Since Colorado has seen so many days above 50 degrees this winter, honey bees have become a common sighting.
When temperatures start to drop for winter, honey bees huddle together to make a cluster and shiver their wings to provide warmth within the hive. Their main goal is to keep the queen warm so the colony can survive. The core temperature in the hive can be as high as 90 degrees. A healthy hive with adequate food storage is more likely to survive: beekeepers leave up to 100 pounds of honey in a hive for the bees to feed on throughout the winter.
What is not normal for this winter?
Butterflies and moths that would normally die off as adults in cold winters have been observed flying around, likely having found sheltered areas to stay alive.
Most grasshopper species die off when winter arrives and only the eggs survive in the soil. Some adults may find sheltered areas and survive part of the winter. In Colorado, there are some species where the eggs hatch in the mid- to late summer, and they will overwinter as nymph grasshoppers. Itap possible to see grasshoppers on these warm, winter days.
But it could be a tough year for grasshoppers. The dry weather may lead to less plant material/weedy plants, which may increase the pressure on irrigated plants such as crops and ornamentals on which grasshoppers survive.
As we move forward into the spring, it is possible for other insects to emerge earlier than normal. This could be a challenge for some, depending on their food source. Insects that depend on pollen and nectar may not have adequate resources available unless flowers are also blooming early.
Itap also possible to have mismatches between plants and insects. If plants bloom earlier than when the insects emerge, they may not be able to utilize food/resources from the plants.
Pest activity could worsen with warm temperatures. They could emerge early and stay active longer, causing more damage. As an example, ticks are a medically important pest that could potentially have an earlier start to the season. The warm weather may also benefit forest pests. Mountain pine beetles are already predicted to increase significantly this summer due to high availability of old, stressed-out pine trees along the Front Range. Ips beetles emerge when daytime temperatures stay consistently above 50 degrees, which impacts the timing of preventative treatment for valuable trees. Drought stress from the warm, dry winter can cause
additional stress, working to the beetle’s advantage.
What can we do?
Healthy plants will better withstand drought, pests and pathogens. Prioritize trees and shrubs in the landscape. New plants, including drought-tolerant perennials, will also benefit from supplemental water while they are establishing in the soil.
If possible, wait to clean up gardens. Insects and arthropods are still utilizing the leaf litter and plant debris even with warm temperatures. Leaf litter can also be a great mulch to help keep moisture in the soil after watering.
Consider water conservation in your garden and landscape planning. We may see tighter water restrictions this summer. Perhaps there are areas of drought-stressed turf grass that could be transformed into a space that supports drought-tolerant perennials, although be mindful that new plantings will need supplemental water until they are established.
After turning on your irrigation system, plan to do a simple irrigation audit to improve coverage and save on the water bill. Follow your local municipality and water provider for guidance on watering your landscape this season.
For more information on insects, plants and managing landscapes in drought conditions, call your local county Extension office or visit the Colorado State University Extension website at.
Lisa Mason is a horticulture specialist for CSU Extension in Arapahoe County.
