Recently, there have been many articles addressing how the winter will affect populations of overwintering insect pests, but how did the recent cold winter affect the incidence of crop disease (the fungus among us)? It, of course, will depend on the type of fungus, but typically most fungi require some basic items: respiration, nutrients (nitrogen or other minerals), water, light (but not in most cases), and specific temperatures.
In general, fungi can tolerate the range of temperatures that typically occur in the place where they have taken up residency. So, fungal disease pathogens that have made a home in the Midwest, generally have developed the ability to tolerate our cold, winter temperatures. Fungi have figured out several ways to survive during cold temperatures, and many produce special survival structures that are thick walled, which can survive extended cold periods as well as extremely dry conditions, within residue or in the soil. After the winter, the fungal pathogens wait until just the right temperature to become active. Plant pathologists will always refer to the plant disease triangle when it comes to plant disease infection on your crops.
|This picture is courtesy of |
Don't forget that some fungal disease pathogens do NOT overwinter here in Illinois. Rust spores blow up from the South and under the right conditions, can infect plant hosts during our growing season. Some examples of rust diseases that infect corn are common rust and southern rust. Soybean rust can be an issue on soybeans, but, fortunately, this disease has not been a yield reducer in the Midwest. Soybean rust has infected soybeans in the Midwest, but historically has been found late in the season, which is not cause for alarm at this time.
|Up close picture of soybean rust (Phakopsora pachyrhizi) pustules on a soybean leaf. Picture taken by Mike Meyer.|
Southern rust on corn: