Probably pythium blight, a common turf grass disease on young spring seeded grass. I would use Heritage fungicide as soon as possible as pythium has a nasty habit of spreading quickly.

Get Headway G or Pillar G if you can afford it, if not get Disarm G. Apply it every 28 days during the summer months, prevents most fungal diseases.

Can you describe the differences between heritage, headway, pillar, and disarm?

Where to buy (locally?)
Cost
Form - liquid spray vs granular
Toxicity to humans
Success speed and rate of success
Advantages/disadvantages?

Thanks

This post was edited by viche on Wed, Jun 26, 13 at 8:40

Read the labels and watch the temperature. In my neck of the woods it is too warm for the popular chemical fungicides from about April through November.

Can you describe the differences between heritage, headway, pillar, and disarm?

Not much. I think all of them have a strobilurin, and pillar and disarm also have a second different fungicide class as well. I'm pretty sure the stobilurins are all effective against pythium, so I would probably just buy the cheapest one.

Where to buy (locally?)

Best bet is John Deere Landscapes or any large turf supply store. You can also buy them online from places like Amazon, E.H. Griffiths, etc.

Cost: Not cheap. Heritage is about 80 bucks for 40 lbs. The others are probably similar .

Form - liquid spray vs granular

Depends on what you are more comfortable with. Liquids are probably better for treating active disease, although I know Heritage G (granular) is quickly absorbed through moist leaf tissue. Granulars are easier to apply to large areas.

Toxicity to humans: Very low, but I believe apple trees are very sensitive to stobilurins.

Success speed and rate of success

Very high when applied properly.

Advantages/disadvantages? The advantage is you will stop and prevent fungal disease. The disadvantage is you are adding yet another chemical to the enviroment, as well as causing some harm to beneficial fungi in your soil. Golf courses use them during the hot summer months, otherwise they would likely lose large areas of turf.

Thanks for the great answers!

It could be one of several fungal diseases, you can't tell from the photos you posted. Besides pythium blight, it might also be brown patch, which is very common on TTTF, or damping off, which affects young seedlings. Before spending $80 on Heritage, I would look at your cultural practices, starting with mowing height. If you are over 3 inches and living South of Baltimore, TTTF is very prone to brown patch. Brown patch is much easier and cheaper to control than p. blight, which many common fungicides (like Immunox) are not effective against. With p. blight, you are likely to see cottony stuff around the spots in the early morning, while the dew is still fresh. It will usually be around the edges of the patch. So ck for that first. If you see that, I would move quickly, because p. blight spreads fast.