Diagnosing turf problems can present a challenge. Whether the problem stems from an insect or a mower, it all just looks like dead, brown grass. Unlike damaged ornamental plants, there is not always an obvious clue that pops out, such as powdery mildew on lilacs, or Japanese beetles chewing on roses.

Turf problems make us dig for clues and work hard for our answers. There are some steps we can take to narrow the field of problems that might be causing an unhealthy lawn.

First, try to determine if the problem is living (biotic) or nonliving (abiotic). Biotic problems include disease, insects or weed infestations. A nonliving problem might involve soil compaction, drought, or herbicide damage. You can distinguish biotic from abiotic by looking at the large picture of the turf area and asking yourself this short check list of questions.

Not many living problems are this widespread (cause: nothing! This turf had sand put over the top of it mixed with a little compost for fall “top dress”)

Chances are that if a problem is stretched across the entire lawn, it’s an abiotic cause. Not many insects or diseases can destroy a lawn in just a few days. So if the problem is widespread, you need to dig a little deeper into the past to find out what has happened that may have caused the problem.

Step two: ask questions about recent past events:

If the problem is not widespread, but confined to a small section of the lawn, and that section hasn’t had any special treatment, you may be dealing with a disease or insect.

Start the disease diagnostic process by looking for patterns. If the pattern is perfect, like a straight line or a perfect curve, then you probably have another abiotic problem.
 

Not many living problems have this obvious of a pattern (cause: leaking hydraulic fluid from a mower)

But if the pattern is more like circles or patches, you may have a disease. The best way to diagnose a disease is by getting a good reference book. Or by submitting a sample to a reputable laboratory that will test your turf for possible diseases and viruses and make recommendations as to how to control the problem and what to do to prevent the problem from occurring again. The University of New Hampshire Cooperative Extension has a Disease Diagnostic Laboratory in Durham. Samples of diseased turf can be submitted at any time by mail, or dropped off in person. 

Step three: purchase a good reference book or learn more about the UNH Cooperative Extension Plant Diagnostic Laboratory

Diagnosing turf diseases takes a lot of practice and a good eye for color and patterns. Once you know what to look for you’ll be able to narrow down the diseases species and focus on a just a few different species that fit the description of your problem. Listed here are a few steps to help you recognize the key characteristics that differentiate turf diseases.

Tug on the grass and see if it pulls up easily. If it does, then you may be dealing with a root or crown problem. Root and crown problems don’t usually have neat, obvious leaf lesions, but more of an overall discoloration of the entire blade. Check the roots for dark brown or black colors or swollen areas like nodules.

If the roots look healthy and white, then you may be dealing with a crown rot. The crown, or the area where the turf plant touches the ground, will look brown, black or yellow. Once you’ve determined whether you have a leaf, root, or crown problem, and you’ve gathered information about pattern, color, and lesion characteristics, a reference book will help you make your final decision.