CHAMPAIGN, Ill., 3/6/24: Winter 2023-24 has been warm throughout Illinois, creating conditions ripe for insects to overwinter, according to scientists at the Prairie Research Institute (PRI) at the University of Illinois.
The state’s average winter temperature was 35 degrees, which is 5 degrees warmer than normal. February ended with temperatures in the 70s and 80s, said Jennie Atkins, PRI Water and Atmospheric Resources Monitoring (WARM) program manager.
The warmer weather has led to higher soil temperatures. Temperatures at 4 inches under bare soil averaged 39 degrees this winter, December–February, 3 degrees above normal and 1 degree higher than last winter’s average. Only 18 days had a state average below the historical average. Also, averages fell below freezing on only seven days, all during the bitter cold period in mid-January.
The coldest soil temperatures were in central and southern Illinois where lows in the teens and mid-20s were recorded. Temperatures were higher in northern Illinois with lows hovering around freezing due to snow cover.
Soils were warmer under sod with a seasonal average of 40 degrees at 4 inches, 4 degrees above normal.
March temperatures began near normal, averaging 40 degrees at 4 inches under bare soil on March 1 with highs in the 50s and 60s and lows in the 40s. Temperatures rose to an average of 49 degrees on March 3.
The warm winter has led to lots of questions regarding insect survival and potential pest issues in the upcoming growing season, said Kelly Estes, PRI state agricultural pest survey coordinator. Generally, warmer temperatures favor insect survivability.
Insects not only overwinter in different life stages, but also in different locations. Some, like Japanese beetles, overwinter in the soil, while others spend the winter months in leaf litter, grass, or under tree bark. Warmer air and soil temperatures will favor their survival, especially with minimal days below freezing or extreme temperature swings.
While the potential for insect survival is now greater, April and May weather can also impact insect populations heading into the growing season. A late cold snap or wetter than average spring conditions can affect early-season pests. Water-logged soils during the rootworm hatch will keep populations of this important pest low.
The Illinois State Water Survey’s WARM program collects hourly and daily weather and soil information at 19 stations across the state. Daily and monthly summaries can be found at the WARM website and in the Illinois Water and Climate Summary.
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Media Contacts: Jennie Atkins, Ph.D. - (217) 333-4966, jatkins@illinois.edu; Kelly Estes - (217) 333-1005, kcook8@illinois.edu
