That is crab grass. The most dreaded lawn weed in my opinion. There is nothing you can do about it this season, only way to get rid of it is to hand pick it. Next spring you will want to put a pre-emergent down. Not sure if it's the same for non-organic, but the rule of thumb for organic is to put down corn gluten meal when the forsythia blooms or after having 3 consecutive days of 50 degrees or higher. Follow instructions closely, timing of the per-emergent is critical to it's success.

Also, raising your mower a bit will help block the weed from overpowering your turf grass. When you cut it that short, there is less competition for sunlight and the weed will easily win out over the turf, especially in times of drought.

This post was edited by SC77 on Thu, Jul 11, 13 at 20:50

If you lives in the south that could be either St Augustine with a fungal disease or it could be crabgrass. But I've never seen crabgrass with a disease like that.

If you live in the north it is almost certainly crabgrass.

Where do you live?
What kind of lawn grass do you have?
How were you watering (Frequency and duration)?

I live in Mass. I don't know for sure what type of grass I have, but most areas around here have some sort of mix of bluegrass, perennial rye, and fescue. I water every other day, 20-30 minutes depending on which zone. Since earlier this week I have been watering every day since I had that week of downtime.

I'm in MA as well. Your watering too frequently, but no long enough. You should water 1 inch per week. Use a tuna can to measure how long it takes your sprinkler to fill it. You won't need as much water if you raise your mower to at least 3.5" as well

Ok, i'll check the output of my sprinklers and adjust accordingly. I was using the sprinkler settings from the previous owner, which seemed to be working very well for him. How many days a week would you recommend watering, assuming they add up to 1"? My mower is actually set at 4", and I mow it once a week.

Typically, you want to water deeply (1 inch) all at once, 1 time a week. But obviously that depends on weather, if you step on the grass and it doesn't bounce back up, its time to water. 4" mow height is great, guess it just looked low in the pic.

Watering frequently, but not deep causes the grass to for shallow roots and tends to encourage weeds

If the temps are above 90 degrees F, then once per week should be enough. Above 100 and you might have to go to once every 5 days.

80 to 90 once every 2 weeks
70 to 80 once every 3 weeks
below 70 and you should go to monthly

This is a guide. Watch your grass to let it tell you when to water. When the blades fold together, water immediately. Then if you did not go the full duration suggested above, water longer/deeper so you can go the full time. When you water too often you are going to germinate the weeds as SC77 says.

Ok, I just put out two tins out and got 1/4" in one hour. I have 9 zones that water individually. So that would mean that I need to run each zone for four hours a week, totaling 36 hours. I do not have a water ban, but can only water from 5pm to 9am, so it looks like i'll have to water during that time span twice a week, and still be a little bit short of 1" for the week, which I assume will be made up by rainfall. Given the output of my irrigation system, does watering once every four days make sense?

dchall, can you find a picture online of what you mean when you say "blades fold together"? And would there be any obvious signs of over-watering? Thanks guys.