Iowa's recent experience with the Polar Vortex and extremely cold temperatures and wind chills has caused some people to wonder which crop and garden pests can survive these extremes.
The ISU Extension Entomology team has been addressing those questions as well as other seasonal buggy issues on the Horticulture and Home Pest News site, www.ipm.iastate.edu/ipm/hortnews/.
Emerald Ash Borer
"Will this cold freeze out the EAB population in Iowa?" The short answer: Probably not…
Cold hardiness research done in Minnesota by Robert C. Venette and Mark Abrahamson (2010) revealed that larvae that acclimated to winter temperatures over 3 months were able to survive lower temperatures (-13˚F / -25˚C) than larvae subjected to cold conditions in a short time (0˚F / 17.8˚C). This is referred to as supercooling. The supercooling point is a temperature far below freezing that insects can withstand through physical and chemical changes in their bodies. Survival varied from 5% in non-acclimated larvae to 90% acclimated larvae. Referring to northern Minnesota winter conditions, the authors stated, "cold temperatures may not completely eliminate the insect…may help to keep populations from building up quickly and may give ash trees some time to recover from initial attacks."
A key consideration in insect survival overwinter is how cold for how long. As an example, the northern 'expansion' of the bagworm is limited by freezing temperatures. When the temperature falls to 1˚F (-17˚C) and stays there for 24 hours, more than 75% of the eggs in the bag can be killed.
The brunt of extreme cold occurred on January 6 and January 7, 2014. Thirty-six hours of subfreezing temperatures (as low as -16˚F/-27˚C) probably weren't long enough to cause significant mortality to emerald ash borer larvae or native upper Midwestern insects. But, on a positive note, bagworm populations will probably be lower in 2014.
Stored Product Pests
We don't expect to see insects in the winter but household pests may surprise us and be active any time they are sufficiently warmed by the heat from the furnace. Examples include the accidental invaders such as boxelder bugs and lady beetles, insects that emerge from firewood, and stored product pests living, eating and growing inside stored products such as bird seed, dry pet food, and stored food in the cupboard.
One of the more common household stored food and seed pests is the Indian meal moth. The adult moths have distinctive two-toned wings that are one-half inch in length. The base of each wing is tan and the outer half is coppery-brown. Indian meal moth caterpillars are slightly less than one-half inch long, have a dark brown head and vary from off-white to light pink in color. Caterpillars live and feed inside a wide variety of stored products but a few leave to wander around the house and will be seen on walls and ceilings.
Control of Indian meal moths and other stored food pests requires locating and eliminating infested products ("locate and eliminate"). Sprays and cleaners are of no benefit and do not solve the problem because they do not get rid of caterpillars inside the infested products.
ISU Extension and Outreach provides research-based information and education to help families make decisions that improve and transform their lives. Learn more at www.extension.iastate.edu.
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