View Full Version : Diagnosis, please?

07-06-2002, 09:57 AM

Can anyone help in diagnosing this condition on my newly planted lawn? The circles start out perfectly round and then grow larger and larger. It looks like all of the grass in the area is not necessarily effected, but I'm not too sure.

I planted the lawn in early/mid May. The seed was a mix of blue, perennial rye and fescue, with a little annual rye mixed in. The condition just started over the last week or so.

Thanks in advance.

07-06-2002, 05:43 PM
What you have is either Rhizoctonia Brown Patch or Summer Patch/Necrotic Ring Spot. These are both diseases. Without seeing the site, I would guess Brown Patch is your problem.

Brown Patch forms on dense, highly fertilized lawns during long periods of hot, moist, overcast weather and night time temps over 60 degrees when the grass is wet. It typically has a "smoke ring" when wet (a dark purplish to gray/black ring of infected grass on the outside margin of the ring). It is common to have grass growing in the center (frog's eyes) after several mowings.

Avoid excess nitrogen, especially in spring. Avoid watering after 5:00 PM in the evening so the grass is not wet through the night. Improve air circulation over the lawn by triming trees and shrubs. Preventitive fungicides are available. Overseed with a grass cultivar that is resistant to Brown Patch (this and your cultural practices are your best long term cure).

Summer Patch/Necrotic Ring Spot generally does not form on newly sodded lawns for the first couple of years. It is a serious problem for highly maintained Kentucky Bluegrass lawns. It occurs when hot sunny days are followed by wet periods. It can become quite sever when the grass is under stress due to heat and is entering summer dormancy. It can be caused by over watering, thatch over 3/4 inches, soil pH over 7 or below 5, unbalanced fert apps, nematodes or soil compaction. It also produces frog eye's (green centers).

The best control of Summer Patch is again the use of resistant grass cultivars, a good mixture of ryegrass, fine fescue and Kentucky Bluegrass seed when overseeding and proper watering. Good luck.


07-06-2002, 10:20 PM

Thanks for the information. It sounds like it is Brown Patch. Is there anything I can do, or should I just let it run its course and change my watering habits. I will admit to watering in the evening, even though I should know better.:(

Thanks again

07-06-2002, 10:40 PM
You can collect the clippings and remove them from your lawn to help prevent further spread. Stop watering at night!!!! This can cause other diseases as well!!!! Water when grass looks a dull gray/green and no longer springs back from your footprint. Early AM watering is best. Practice good mowing, watering and fert cultures. Especially inportant to use a sharp blade when you mow. Don't mow low. 3 - 3.5 inches this time of year. Don't put lots of fert down in spring. No more than 1 lb. N per 1000 square feet in spring. Don't fert in heat of summer. Fert late April, June (if you water grass when water is needed), Aug/Sept and Oct/Nov. Fungicides are best applied as preventative, before disease infects lawn. With brown patch you could benefit from fungicide apps now. Good luck.