Not all insects affected by cold

By Tom J. Bechman
Those who have wanted a cold winter to ‘kill off insects’ got what they wanted- a cold winter. Did it really impact important crop pests?
A new panel of Indiana Certified Crop Advisors tackles a question about the possible influence of cold weather on insects.
Question: We’ve had the coldest temperatures in 20 years. Which insects will be affected by the cold winter? Can I anticipate cutting back on insecticide costs?
Jamie Bultemeier, Great Lakes Lab, Ft. Wayne: The unusually cold winter could potentially reduce survival rate of insects that over winter in crop residue and the top few inches of the soil. Insects have two modes of over wintering- stay in the cold north and try to survive or head south for warmer weather, not too much different than humans! Insects like black cutworm, corn earworm and leafhoppers head south for the winter where cold weather has had significantly less impact.
Gene Flaningam, Flaningam Ag Consulting, LLC, Vincennes: Insects that do not migrate into the Corn Belt might be affected somewhat. The first group of insects I would consider affect the root system: corn rootworm, grubs and wireworms are some common pests we deal with on an annual basis. European corn borer will also over winter in corn residue. The survival of those insects will be somewhat affected by cold weather. Insects that migrate into our area will be delayed due to cold temperatures southern states have experienced. This will have some effect on insects such as: armyworm, cutworm, corn earworm and potato leafhopper.
Tom Stein, Ceres Solutions, Templeton: The abundance of insects in any one year depends upon much more than winter weather. That’s not to say that some insects won’t die as a result of extremely cold temperatures, but most will live to see spring. Native insects know how to survive in extreme weather conditions by finding shelter under plant debris, burrowing into the soil and migrating to warmer climates.
Bultemeier: Insects that spend winter in the north have often adapted for cold weather. Impact of weather may be offset if insect population going into winter was higher or spring weather is favorable for increased survival. With higher profitability the last few years many growers have taken a proactive approach to utilize control measures to protect from insect damage. With tighter budgets it’s possible to take a wait and see attitude. Scouting will be critical, and the risks are greater. Remember that as profitability of the crop reduces, so does your tolerance to risk.
Flaningam: Do not eliminate those preventive seed treatments. Be prepared to adjust pest management for insects that migrate into our area.
Stein: Insects can avoid freezing by going into a process that creates a chemical similar to antifreeze. It keeps body liquid fluid in freezing conditions at temperatures as low as minus 30 or perhaps minus 60. Scouting and following best practices for integrated pest management will be just as important this season as in any other year.