10/2022 Issue: Over Wintering Pests

By: John Moore, MSc

Insect survival strategies

Insects are adapted to survive varying climates, wide shifts in temperature, and periods of adverse environmental conditions. Insects use both behavioral and physiological adaptations to combat freezing temperatures and increase their chances of overwinter survival. Many insects maintain a low level of activity during winter months while others enter diapause, a type of dormancy. Freeze susceptible or freeze avoidant insects produce many antifreeze compounds to reduce the lethal freezing temperature of their bodies, such as alcohols, sugars, and ethylene glycol (the same compound found in car antifreeze). They exhibit behavioral shifts and seek out dry, protected overwintering areas such as behind tree bark, burrowing into the ground and inside refuse piles, etc. Freeze tolerant insects do not freeze entirely, but instead internal fluids freeze which draws moisture out of living cells to reduce their lethal freezing temperature.

Insects are predominantly freeze avoidant in cool to mildly cold areas and freeze tolerant in cold areas. Insects aid in winter survival through partial dehydration and reduced feeding, which reduces the chances that excess water within their cells or guts will freeze. Some insects survive winter at a specific stage of growth that is more protected from the elements, such as eggs in a protective egg sac or pupae encased in a hard cocoon, which do not require food or water. Remember, insects over winter and go into diapause because the resources they need are not available in the winter.

Many of the more common insects that over winter in structures do so in the adult form. When we approach the summer solstice (Sept 21^st) the light dark cycle or photo period of the insects begins to change their behavior. Reproduction ceases, feeding reduces or stops all together and they begin exhibiting what is termed diapause seeking behavior even if it is still very warm outside. This just means they begin looking for a place to spend the cold months. Unfortunately, many of our businesses, factories, homes, garages, offices etc. have the perfect microenvironments that they seek. Cool (not cold), dark, low humidity, no wind. Once inside, they can be problematic all winter long. If they are too warm, they will remain active and fly toward lights. Therefore, insect light traps can be so effective if properly placed on the interior of the structure. Residual pesticide applications can help reduce the number of insects that gain entry to the structure. However, the best opportunity for this type of treatment is from the last 2 weeks of September to first 2 weeks of October.

Here are some of the more common ones to look out for.

Boxelder Bugs

During the fall, boxelder bugs become a major nuisance as they congregate and enter homes by the thousands. Boxelder bugs primarily crawl into structures from the ground level but also fly to higher elevations. Their primary route of entry includes gaps in soffits and chimneys, electrical wiring cutouts, garage doors, poorly sealed windows, and especially underneath siding and trim pieces along siding. They will congregate in warm places in a home. Although Boxelder bugs enter a state of diapause, they can quickly become active even in the dead of winter on mildly warm days.

Asian Lady Beetles

Asian lady beetles are native to eastern Asia and considered an invasive species in the US that is an increasing threat to native species. Asian lady beetles produce an unpleasant odor when frightened or crushed and tend to stain surfaces. They have also been known to bite humans. Asian lady beetles enter homes in fall months by the thousands through every imaginable crack, crevice, and opening, and gather in warm places once inside.

Stink Bugs

Stink bugs are pests of fruits and vegetables, which use their piercing sucking mouthparts to damage crops. Stink bugs such as the brown marmorated stink bug are highly attracted to light. External and interior lights should be reduced during times of heavy stink bug movement. They start the search for overwintering in late summer and can become a severe nuisance inside structures. They will congregate in warm places once inside a home. Stink bugs are difficult to control due to their size and large numbers.

Cluster Flies

Cluster flies are strictly parasites of earthworms and do not present any known human health hazards. These slow-moving flies become pests as they hatch in late summer and early fall. Cluster flies may be present in large numbers and are difficult to eradicate once inside the structure. These flies are often located in areas that are difficult to access for treatment such as attics, wall and roof cavities, window frames and soffits. Cluster flies are especially prevalent in homes with multiple stories, attic spaces with windows, and gaps around windows, doors, and chimneys.

Again, once inside, properly placed Insect light Traps are often your best control option.