Common Turfgrass Diseases

Ascochyta Leaf Blight: (most common disease we see) 

This pathogen lives in the thatch layer of the grass plants. It usually begins to manifest when there is a dry spell that was preceded by a wet period of time. The blight comes on strong and spreads rapidly. Symptoms of Ascochyta blight look as though the grass is not receiving enough water. Often the grass looks "straw colored" or "bleached" in random areas as if the sprinklers are not running resembling drought or dormant looking grass throughout the lawn. Size of the areas are random, ranging from softball size to the entire lawn appearing dead or dormant. The pathogen can also spread from the tires of your lawn mower, your shoes, and even thru water particles.

Causes: Over watering, Dull mower blade, Cutting height too short

What to do for all diseases listed below: 

  • Stop watering! You are actually making it worse when you water the lawn even though it looks like its' thirsty!
  • Raise mower height to 3"+ immediately and cut when dry if possible. (GB cuts grass at 3" or more all year)
  • Sharpen your lawnmower blade most importantly! This pathogen enters the tip of the leaf blade and begins killing the tissue from the tip of the blade downward towards the crown of the plant.
  • Fungicide program. Allow us to apply fungicide on a curative basis when it pops up, or to be safe we can start a preventative program beginning in June and applying every 21-31 days thru August to ensure we prevent it from showing up on your lawn. We recommend a minimum of 3 fungicide applications per season pending on environmental conditions.

Red Thread:

We come across this disease quite often as well mainly on fescue lawns. When looking closely you can actually see 'red hairs' coming out of the tips of the fine fescue leaf blades. Typically it shows up in late June extending into late August. We see it mainly on lawns that are predominately filled with fine fescue. Fescue is a type of grass that is much thinner than bluegrass, almost "needle like." Although fine fescue is found anywhere in most lawns. Fine fescue is common in lawns that are shady since it is considered a shade tolerant grass. This type of grass is what you would find in any shade blend that you purchase. Use the same practices mentioned above to fix the problem.

Necrotic Ring Spot:

This disease is less common but we still see it pop up during the same time as all the other diseases which runs from late June thru August. This particular disease is in the soil so it requires more steps to control it. We typically come across this on lawns that were sodded and where there is or was a wooded area cleared away to make a lawn. Necrotic ring spot is easy to diagnose. They are random size rings of dead grass with green grass in the middle slowly creeping inward and further outward killing the grass.

What to do: A combination of cultural practices such as early spring aeration, de-thatching and applying a fungicide in the spring will help greatly. Apply fungicides April/May then late June thru August. It is difficult to fix the problem once it has already shown up. An aggressive fungicide program has worked in my experience but it requires a lot of attention. It is also best that if or when it does show up, to apply fungicide to prevent it from popping up in other possible portions of the lawn. Continue a heavy aerification program in the spring and fall along with fungicide in order to prevent Necrotic Ring Spot. 

Powdery Mildew: 

This disease is more of a nuisance that anything. A white powdery residue is found on the grass plant. It is typically located in shady areas with too much moisture. It usually never kills the grass plant. The best control measure is to cut back on water, increase air movement if possible and thin out your trees and shrubbery to allow more sunlight into the location. 

Fairy Ring:

Another disease that is common and more of a nuisance than anything. Shows up as dark circles of grass in the lawn ranging from soccer ball size to 20-30ft diameter. Sometimes if your lucky you will see an entire circle of mushrooms show up along the whole outline of the ring making a complete circle. The best thing to do is live with it. Its a soil fungus not worth fighting. On my end I can try to match up the existing grass with an iron product to darken the entire lawn and blending the dark green circles making the symptoms less noticeable.