By Brett Arenz
The improvement of plant health (and yields) can only be successfully achieved after a clear understanding is made of what is reducing plant health in the first place. This is where the Plant Disease Clinic (PDC), can help. The PDC is based on the St. Paul campus at the University of Minnesota. It provides diagnostic services, specializing in microbial pathogens of plants. The PDC diagnoses thousands of samples each year from state and federal agencies, the agriculture and horticulture industry, and the general public. We are also part of the National Plant Diagnostic Network (NPDN) which monitors and tracks the movement of plant pathogens in the U.S.
For single season crops like corn and soybean, it is particularly important to pay close attention to plant health problems early in the growing season. Diseases that start in June will tend to have a much greater impact on final yields than diseases that don’t get started until much later in the summer. Much of Minnesota has just experienced a period of cool and wet weather, which are perfect conditions for some diseases that attack seedlings. There are multiple pathogens and abiotic issues that can cause similar symptoms and a misdiagnosis based on an incorrect assumption can lead to expensive and wasteful treatment applications, as well as not fixing the original problem!
Accurate diagnosis also requires high quality and timely samples. Plants that are symptomatic but still living are typically the best to submit. Every fall the PDC receives soybean samples submitted by growers that suspected they had a disease issue but were simply too busy during the active growing season to submit them. In many cases the dead soybean plants are impossible to diagnose as saprophytic organisms have colonized the tissues and it is not possible to be sure which organism caused the initial disease.