What is the disease risk if I use cover crops on my farm? This has become a popular question over the past couple of growing seasons. To answer it, we called on Andrew Friskop, assistant professor and cereal crop Extension plant pathologist at North Dakota State University:
To begin, there is not a one-size-fits-all answer, and that’s good! North Dakota has a wealth of diversity in crop production, soil types, cultural practices, crop inputs and many other factors. One way to help simplify the thought process and understand risk is to think about the corners of the disease triangle (host, pathogen and environment); we will use leaf rust of rye as our example.
Host: What is the host range for leaf rust of rye? Rust pathogens tend to be very host specific, meaning that the rust we find on rye will not cause disease on other crops (i.e., sunflower, dry beans, wheat and barley). Just knowing that leaf rust of rye will be confined to rye drastically reduces potential disease risk. Other diseases that might be associated with cover crops can have a much larger host range (i.e., wheat streak mosaic, ergot, soybean cyst nematode). I encourage everyone to do homework on the pathogens (diseases) affecting a cover crop plant species and determine whether a relationship exists with a field crop.
- Environment: Arguably, the biggest driver of disease epidemics in North Dakota is the environment. Development of leaf rust of rye is favored by warm temperatures and prolonged periods of leaf wetness (dew or rain). These conditions are more common starting in June and helps explain why we see leaf rust near grain fill and/or during the fall. In North Dakota, diseases can be found in hot, cool, dry and wet environments, so understanding the environmental profile of a pathogen helps determine the associated disease risk.
- Final thought: When determining disease risk associated with cover crops, consider the most problematic diseases in your field crops and start asking questions if a disease risk relationship exists. Then, use the disease triangle to help guide conversations related to the topic.
Andrew Friskop can be reached at email@example.com. Abbey Wick is an Extension soil health specialist at North Dakota State University.