A warmer, wetter winter has caused higher-than-normal soil temperatures across the state, which could be helping agricultural pests survive.
According to Jennie Atkins and Kelly Estes of the University of Illinois' Prairie Research Institute, Illinois temperatures averaged 33 degrees for the winter season, 4 degrees above the long-term average. Winter 2019-20 ranks as the 12th warmest on record for the state.
The state has also experienced higher soil temperatures. At 4 inches under bare soil, temperatures have averaged 37 degrees from December through February, 3 degrees warmer than the long-term average.
All Illinois regions had temperatures below freezing during the season. However, these periods were generally short, with daily highs often rising to more than 32 degrees. Seasonal highs reached into the 50s.
While warmer temperatures favor insect survivability, repeated swings in temperature (alternating between cold and warm) are more detrimental to pests, Atkins noted. However, Illinois didn’t experience dramatic swings in temperature, so the mild winter could be setting the stage for a comeback for some field crop pests.
Estes advised farmers to be observant this spring. Weather events in April and May can impact insect populations going into the growing season, especially if the state has another very wet spring or late cold snap.