Please help ID what's killing my lawn

skeeter080September 8, 2009

It is a perennial rye, fescue, KBG mix that I seeded a couple years ago. Looks great every spring, then as summer goes on it starts to die off. We've had lots of rain this year so I haven't been watering much, but the same thing happened when I watered last year. It's been cut at 3 1/2 - 4", it is now down to 3" in the pictures.

Here's a before picture of my little guy enjoying dad's awesome lawn from earlier this spring:

Closeup of the can see how some blades are starting to go, others dead, and some nice and green:

Zoomed out:

Thanks in advance, let me know if more info is needed.


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donaldb(5B Worcester, MA)

Nice photoshop work on the child.

    Bookmark   September 9, 2009 at 10:00AM
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dchall_san_antonio(8 San Antonio)

You're following the plan just fine. I'm going to suggest (and I NEVER suggest this) a soil test. If they have a separate test for micronutrients, get that, too.

Where do you live?

    Bookmark   September 9, 2009 at 12:01PM
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I live near Hagersville, Ontario. I'm thinking this is leaf spot affecting the common KBG, but that's just a guess really. I'd like to overseed with a better quality seed but I'm having trouble finding any of the improved cultivars.

    Bookmark   September 11, 2009 at 8:32PM
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When were the pictures taken?

It looks like you're mowing too high...

Does not look like Leaf Spot to me, take a closer picture of the grass blade so I can tell you what it is.

    Bookmark   September 12, 2009 at 5:24PM
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I was mowing at 4" for most of the summer...4" setting on the mower which could be a bit higher than 4". Cutting it at 3" now and I think I'll stick with that for next season.

The first picture with the lawn looking good was May 29, the rest were taken a few days ago but the lawn's looked like that since July anyways. I'll try to take another closer shot tomorrow. Thanks.

    Bookmark   September 12, 2009 at 7:27PM
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mccorma(z7 GA)

Looks like a fungal problem. I agree that mowing at 3-4" sounds very tall for KBG, maybe at that height you are not getting the lower part of the blades to dry out from dew; not enough sun/air and inviting a fungal problem. I have "tall" fescue here, and only mow that at 2.5" or so.

    Bookmark   September 12, 2009 at 10:21PM
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It's probably the rye portion of your lawn dying. When heat hits rye it gets toasted. I had the same problem actually, and just deleted my pictures but they looked exactly like yours.

    Bookmark   September 12, 2009 at 11:43PM
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I always thought 'the higher the better' seemed to be the best way. If I cut at 2.5" I would be cutting every day to stick to the 1/3 rule.

I really don't think it's just the heat. If you look at the 3rd picture full size you can see a better closeup of the problem. The end result is dead grass blades but it starts out with a black spot that spreads to the rest of the grass blade. I will try mowing shorter for the rest of the season and next year to see if that helps.

    Bookmark   September 13, 2009 at 6:44PM
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In the absence of rainfall, yes, the higher the better. However, if excess moisture/rainfall is present, then cut no higher than 2.5". The problem is that the higher cut traps moisture making the turf more vulnerable to insect and disease damage.

Why would you be mowing every day to follow the 1/3 rule? Is your grass growing that fast?

Not even at the golf course we mow the Tees every day, and those are cut a half inch...

Unless you are watering your lawn every day and fertilizing every 30 days, there no logical reason why your grass will grow 33% in 24 hours...

Where are you located?

Give me your zip code.

    Bookmark   September 13, 2009 at 8:49PM
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Hagersville, Ontario (Canada) N0A 1H0
It was growing very fast in the spring. Cutting it at 4" was done every 3-4 days, so about 2" in that time.
I fertilized late spring with soybean meal at approx 15lbs/1000 sq ft. Did the same amount of cracked corn about 6 weeks later in the hopes it would act as an antifungal but that didn't seem to work...the birds loved it though.

    Bookmark   September 14, 2009 at 7:46PM
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dchall_san_antonio(8 San Antonio)

Please let us know how 3 inches works for you. Taller is better seems to be the consensus except for the Elite varieties of KBG.

You might have not used enough corn. 20 pounds per 1,000 is what is usually used to get rid of fungus.

    Bookmark   September 15, 2009 at 3:53PM
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I think I'll stick to 3" and put down corn 2 or 3 times in the spring a few weeks apart to try and prevent whatever fungus this is.

    Bookmark   September 15, 2009 at 4:33PM
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Keep the kid off the lawn. I bet you he pee'd on those spots!

    Bookmark   September 16, 2009 at 12:43PM
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Skeeter, your summer temperatures seem to be on the mild side (79 high, 58 low average in July) and rainfall seems adequate for turfgrass growth.

Unless you have an old junky Perennial Ryegrass in your mix, then the affected grass is Kentucky Bluegrass.

Perennial Ryegrass should trive during the summer in your climate, and suffer during the winter unless there's reliable snow cover for several months.

The two most common diseases of PRG are Gray Leaf Spot and Rust (not severe) Crown Rust, however, will kill the plant. Rust can occur due to lack of growth either from lack of rain or too much heat and lack of fertilizer.

Greay Leaf Spot usually happens in late summer and due to morning dew or night watering (night rainfall as well) extended periods of leaf wetness during the day and at night. This is a very easy disease to control with fungicide applications. Rust can be managed with proper fertilization and rainfall/water. Fungicides are also available to combat the disease, but usually not needed if follow above.

I suspect your Kentucky Bluegrass can be suffering from either Leaf Spot (very common disease on KBG) Dollar Spot, or Summer Patch. All of those diseases can be "controlled" with fungicides, the most diffucult one is Summer Patch.

With your current temperatures, your grass should be recovering very well right now or is it?

Seventies during the day and fifties at night are ideal for cool season grasses provided that moisture/rainfall is present.

I suggest you overseed with better cultivars, or spray fungicides to avoid reoccurance.

    Bookmark   September 16, 2009 at 8:47PM
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