Co-authored by Nathan Kleczeski and Nick Seiter, University of Illinois.

Many in the Illinois agricultural community are wondering what effects the recent extreme cold might have on pests and pathogens. While it would be nice if the cold temperatures we are experiencing could help to reduce our potential for pest damage, past experience tells us that the most serious pests we deal with are unlikely to be impacted much by these conditions.

Many of the pathogens and insect pests that commonly affect field crops in Illinois are well adapted to survive our winter conditions.  In many cases, pathogens produce recalcitrant survival structures (e.g. cysts in soybean cyst nematode, oospores in Phytophthora, sclerotia in white mold).  These structures allow the pathogen to survive extreme conditions including cold, drought, and flooding. Different species of insects overwinter in different life stages, including eggs (for example, western corn rootworm), larvae (Japanese beetles), pupae (corn earworm, though they do not survive the winter in most of Illinois), or adults (stink bugs). The overwintering stage has characteristics that help these insects to survive the winter, either by adjusting its physiology to better survive the cold, seeking out an overwintering site that protects it (such as soil, tree bark, or leaf litter), or both. The overwintering sites that insects find mean that they are not experiencing the same temperatures that we are when we venture outside. Wind chill has little effect for this reason (even though it has a major, unpleasant effect on us).

Extreme cold temperatures can impact some insects and plant pathogens, particularly those that may not overwinter as well (e.g. powdery mildew).  When cold weather pushes into the Southern regions of the country it can push certain diseases, such as rusts, further south, delaying disease onset in Illinois and other regions further north. The same is true of migratory insects, such as black cutworm and fall armyworm, which do not usually overwinter in Illinois; colder temperatures during winter often delay the arrival of these insects, and may ultimately lead to lower numbers. The opposite is also true – warmer than normal temperatures during the winter can allow these migratory insects to become a problem earlier in the season.

Article originally appeared in the Bulletin. Read the full article here: http://bulletin.ipm.illinois.edu/?p=4479.

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About the Author: Nathan Kleczewski

Dr. Nathan Kleczewski is the Plant Disease and Entomology Specialist for GROWMARK Agronomy Services and their technical agronomist for the eastern and southern territories of Illinois. In his role, he assists member companies with troubleshooting day to day issues encountered in fields, assists crop specialists with management recommendations, and works to train and educate crop specialists in practical, sustainable, and economical management of diseases and pests in crops grown in the United States and Ontario. He has worked extensively in the field of applied field crop and vegetable pathology since 2013, serving Illinois (2017-2021) and Delaware (2013-2017) as their extension field crop plant pathologist. He worked at FMC as a research plant pathologist working to evaluate and develop new fungicide, nematicide, and biological products, and has post-doctoral experience from both Purdue University and Indiana University. He earned his doctorate in plant pathology from The Ohio State University in 2009 and his Bachelor’s degree in plant ecology and evolutionary biology from the University of Wisconsin-Oshkosh in 2004.