FROM THE LAWN INSTITUTE HELPFUL HINTS


HELPFUL HINTS


FROM THE LAWN INSTITUTE LAWN DISEASES


names from the large patch-like symptoms they produce, whereas Dollar spot, Leaf spot, Copper spot, etc. produce very small lesions on grass leaves that look like spots. Another example is Fairy ring which produces large rings. While many of these symptoms are sometimes easy to identify, often times they are not. Te best way to properly identify causal organisms in those cases is to submit a sample to a plant diagnostic laboratory for identification under a microscope.


Diseases often impact many species of plants—and grasses are no different. As is often the case, there are a complex array of factors that affect how plants and other organisms interact with each other including nutrition, plant stress, moisture, temperature, management practices, and more. However, one common theme among all natural grass disease infections is often referred to as the Turfgrass Disease Triangle. Tis triangle consists of three factors that include a susceptible plant, a disease-producing organism, and a favorable environment for infection. It takes all three factors for a disease infection to occur.


Most turfgrass diseases are caused by fungi, but there can be other sources of infection from bacteria, viruses, parasites, nematodes, or other organisms. Tere are well over 100 diseases that can occur on lawns and other grasses, but fortunately only around 25 or 30 of them are routinely problematic.


Tey each have a scientific name of the causal organism, and a common name of the disease it causes. For example, the lawn disease Brown patch is caused by Rhizoctonia solani, whereas other patch diseases such as Summer patch and Take-all patch are caused by Magnaporthe poae and Gaeumannomyces graminis, respectively. Many of these organisms often only affect certain species of grass while not impacting others, so from an identification standpoint, this helps narrow in on the causal organism by somewhat eliminating others.


Different causal organisms produce different symptoms which can also help with identification. For example, Brown patch, Large patch, and Take-all patch get their


For more information on lawn care and helpful “How to” tips, visit The Lawn Institute at: www.TheLawnInstitute.org.


TPI Turf News September/October 2022 9


In addition to the causal organism, the other two sides of the disease triangle are equally as important. Understanding which species of grasses are susceptible to different organisms, and what type of environment is likely to favor infection, are key factors in preventive disease management. If relying only on the symptoms of plant diseases, then you have to wait until after a grass plant has been infected to treat it. While this approach is valid for many diseases, there may be instances where it is important to treat before infection, thus preventing the symptom from ever appearing in the first place.


A good understanding of the disease triangle lays the foundation for disease management in grasses. Tere are many safe and effective fungicides on the market that treat many lawn diseases, but proper identification and selection is key. Tere are several university websites, in addition to Te Lawn Institute website, that describe various symptoms and treatment options to effectively control lawn diseases before they get out of hand. Although, it is also important to know that grasses are very resilient plants and sometimes it is just a matter of letting them grow through the damage and come out the other side.


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