Pythium Blight Disease
Question / Answer

The following statements are partial questions to a lawn that was turning brown, which turned out to be Pythium Blight. The visitor sent photos and other information on how she was taking care of her lawn. Pythium Blight is a very fast spreading, destructive disease, that in most cases is avoidable. Here is some of the dialog back and forth. We hope this can also help others. 

From Website Visitor:  ... I have to say I have more yellow and brown patches and areas than I've ever had. my lawn is no longer nice and Lush and green.... We've been getting a bunch of rain... But what do you suggest?

Answer to Lawn Problem (Pythium Blight)

Thanks for the photos. They were a great help. 

From what I see and the conditions you described, it appears you have Pythium Blight. This disease is a summer disease and is a type of mold. Normally Pythium is a beneficial mold but when conditions change that favor the mold's rapid increase it can become a plant disease. The primary turf species it attacks is cool season grasses. Because of where you live there is almost a 100% possibility of you having a cool season grass, such as bluegrass, fescue, ryegrass or others. 

Pythium Blight attacks lush turf grass that has somewhat poor drainage that has been over-watered where moisture doesn't have the time to dry out. It is considered one of the most dangerous turf diseases because in severe cases it can kill a large portion of beautiful turf in just 24 hours. Over-fertilization makes it worse. The disease is active not cannot be a problem in cool weather. Where excessive moisture and nutrients are present, it sits in the soil waiting for the temps to heat up to over 80 and becomes most aggressive at 95 degrees. 

It always forms in small round circles only 4 to 6 inches in diameter. No more than 9" but spots can coalesce into larger spots or streaks. In wet areas, the disease follows the flow of water being worse in the most wet areas and can make streaks surrounded by spots in a little less damp areas. In the early stages of the disease the grass may appear water-soaked and dark. Then the grass starts to turn from green to light tan or brown. In early morning the blades can have a cottony material that appears, but not always. 

i mentioned the best time to water. This is turf science 101. Whoever told you to water at 2 to 4 in the morning every single night was dead wrong. It is now and always has been considered the absolute worst time to irrigate your lawn, with a few exceptions. Here are the facts on irrigation:

In summer if you choose to water every day, the best time is in the afternoon irrigating lightly to cool the turf while making sure the turf has enough water to remain actively growing. The grass gets moisture and dries before causing any problems. However, irrigating in the morning at or after sunrise or later in the morning is preferable. Only water about once or twice a week deeply. Irrigating in late evening or very early allows the moisture to remain for extended times and gives rise to diseases such as Pythium Blight. This is such a feared disease on sports turf that only when absolutely necessary will anyone irrigate at night. It is one of the only diseases that you can actually see spreading, it can spread that quickly.  

There are fungicides that can control it. You should be able to purchase Cholorthanlonil out there unless you have restrictions against it. It has a wide range of uses. Follow the directions on the label. 

Continue to follow the directions I gave you for using the Bountiful Harvest Biostimulant and Nutrient Supplement. It will help tremendously and also check into the fungicide. 

I hope this helps. 

---

Pythium Blight back to Lawn Care Academy Home

Share This page: