Home --> Field Crops --> Diseases


Diseases that can affect yield and quality of field crops in Illinois are numerous. For plant diseases to develop, certain components of the disease triangle must be present. These components are a susceptible host crop, a plant pathogen able to infect the host crop, and an environment that favors disease development.

In general, plant diseases of field crops in Illinois are caused by biotic pathogens belonging to one of four groups: bacteria, fungi, nematodes, and viruses. Examples of important diseases that cause losses in Illinois field crops can be taken from each of these pathogen groups. Tactics used to manage these pathogens can vary, so it is essential to know the cause of the problem.

Management practices designed to reduce plant diseases affect specific components of the disease triangle. Multiple practices need to be deployed to limit more than a single component, an approach known as integrated disease management. Integrating different management practices often results in better disease reduction and helps reduce selection pressures. Pathogens are affected by selection pressures when certain individual management practices are used (i.e., some host-resistant genes and some fungicides), and this can result in new "races" of the pathogen or fungicide-resistant strains of the pathogen being selected.

The first step in managing a plant disease is to diagnose the problem. Diagnosing a disease from symptoms alone is not always possible, and some pathogens can cause similar symptoms. Misidentification can lead to inappropriate control recommendations (e.g., applying a fungicide to control a bacterial disease), so properly identifying the problem is critical. Magnification with a hand lens or microscope may help in observing spores or fruiting bodies of some plant-pathogen fungi. When diagnosis is not possible with the tools and resources you have available, collect and send affected plant samples to a plant diagnostics lab. The University of Illinois Plant Clinic serves Illinois producers during the growing season.

Copied from Chapter 14 of the Illinois Agronomy Handbook
Carl Bradley, Author

2019 Bulletin: What impact will late planting have on crop diseases?
Most Illinois producers are behind in getting corn and soybeans into the ground this year as a result of persistent rains and cool temperatures.  Some people are wondering what this...

2019 Bulletin: New post on wheat head blight available
Wheat is starting to approach heading.  What should producers do to determine risk for Fusarium head blight and suppress this disease?   Click here to access the new article on...

2019 Bulletin: Cool season viruses in wheat
Currently, most small grains are approaching jointing or just past jointing in many parts of the state.  Now is the time that you most likely will start to see early...

2019 Bulletin: Early season diseases in soybeans
Now that the soils are warming, some producers are discussing planting soybeans in the ground.  When considering early planting of soybeans, there are two diseases that should be considered: 1)...

2019 Bulletin: Remember to check your hybrids for tar spot ratings, scout your fields
It is that time of year again.  Soon corn will be in the ground, and the 2019 field season will be taking off.  It is no surprise that I spent...