If you see concentrated areas of damage in your lawn, you first need to recognize what is causing the damage: insects or disease. To determine exactly what could be causing it, the best thing to do is send in a sample to your local university extension office. A professional will be able to run a diagnosis and recommend suggestions to you. In the mean time, you should do what you can to learn more about what could be damaging your lawn. This blog covers the topic of lawn disease: what a lawn fungus is, how to spot it in your lawn and how to treat and prevent fungus outbreaks. If you are able to determine the damage in your lawn is being caused by insects, visit our Insect Control blog instead.
What is a Lawn Disease?
Most lawn diseases are caused by a form of fungus. Fungi lack chlorophyll and do not engage in photosynthesis, meaning they are unable to produce their own food like most plants do with sunlight. To survive, the fungi need to obtain energy as a means of feeding off of either dead organic matter (and convert the nutrients in dead organisms into energy) or find and take over a host plant. Some common locations you will find fungi in your lawn will be on dead leaves or in excessive thatch.
Fungi spread through spores, which are easily transferred through wind, rain, mowing and simply walking through a fungi outbreak. Once transferred, the spore penetrates into the host plant, feeding and growing until it has taken over the host.
During peak fungus season (late June–late September), a fungus can produce and discharge up to 100,000 spores an hour. This is because of the rising temperatures during this time of year, which provide warm, humid environments for spores to grow in.
What are the Symptoms of Lawn Disease?
For fungus to spread and be present, there needs to be three main factors:
a) a host, living or dead organic matter (thatch and leaves),
b) the right environmental conditions, such as shaded, moist areas to grow in,
c) and the pathogen.
These three factors are also known as the disease triangle. All three must be present for the fungus to grow and spread.
If a fungus is present in your lawn, it will present itself in circular or irregular patterns of damage as seen in the below left image. It will have a clear dead zone where the fungus has fed, and a lighter yellow/brown ring around the outskirts where the fungus is spreading. You can see this in the below right image.
Be proactive; be on the lookout for damp shaded areas that hold more moisture than other parts of your lawn. These areas may or may not have excessive thatch or other dead organic material. If you have areas that match this description, it is time to treat your lawn as these pose the greatest threat of an outbreak.
A good rule of thumb is that by the time your azaleas are showing color, you should be able to very clearly see if your lawn has a fungus.
Some of the many common lawn diseases are brown patch, large patch and grey leaf spot. See the corresponding pictures below.
How Do I Treat a Lawn Disease?
The best way to treat grass fungus is to be proactive and treat at the first sign of damp lawn areas and not after the fungus has taken hold. This can be done with a simple application of a systemic fungicide which the plant will absorb. A systemic fungicide will also help to suppress the fungus after infection.
With fungicide, you get what you pay for, but some action is always better than none! A few recommended options are listed below:
If you already have fungus, stop what you are doing and go purchase a topical fungicide and treat the area immediately; be sure not to mow over that area or walk on it. Each area may take several treatments. Apply a second application in approximately 21 days. You may need a third application as well in three weeks just to be safe.
A word of caution: be sure to check your lawn and treat for fungus prior to any fertilizing/feeding this spring. Most fertilizers contain nitrogen, which fungi love. If you feed your lawn prior to putting a fungicide down and you have a fungus, that fungus will expand exponentially. This will be disastrous for your lawn.
Armed with this new knowledge, go check your lawn, treat the problem areas or potential at-risk area, and get to spending more time enjoying your lawn instead of working on it.