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Old 02-08-2011, 07:56 PM
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First recorded activity by GardenBanter: Aug 2011
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Default Why is my lawn dying?

Can anybody help me identify the problem with my front lawn?

Up until about six weeks ago it was, or at least appeared to be, perfectly healthy. Then small yellow spots about the size of a fist started to appear all over, which grew bigger and more numerous and began to join up producing areas of dead grass a couple of feet across. Whatever it is it is spreading rapidly. I estimate that before the end of the growing season there will be nothing left to grow.

My thoughts are as follows:

1 Clearly not drought. I live in the north east. It's been wet :-((

2 Clearly not bitches urine. There would have to be a hell of a lot of them (there aren't any in the neighbourhood that I am aware of) and it would have to be a concerted effort on their part to do this much damage. There is no telltale ring of lush green grass at the margins of the affected areas and the affected areas are initially too small and too numerous.

3 The lawn was new from seed September 2009 (50% Fine Leaf Fescue, festuca rubra litoralis; 30% Chewings Fescue, festuca commutata; 20% Bentgrass, agrostis capillaris). The site was heavily compacted so I rotovated the topsoil, barrowed it off site, rotovated the subsoil to a depth of 1 foot, graded it (it's a sloping site) and then barrowed to topsoil back. Compaction is definately not an issue. Neither is thatch. I wouldn't have thought one and a half seasons would be enough for serious thatch to develop but it was scarified in the spring anyway.

4 I don't think ph is the problem. I tested the acidity of the soil before sowing at several points and it was 7. I have been plagued by worm casts so have applied iron sulphate spring and autumn. This has reduced to ph to 5.5-6 across thw lawn. Whilst I realise that messing with a soil's ph can affect the turf, from what I've read 5.5 isn't going to cause a problem. Anyway, it was 5.5-6 last summer and the lawn was very healthy. I have re-checked the ph, and it's still consistently 5.5-6 both where the grass is dead and where it still appears to be growing healthily, so I don't see how acidity can be a problem. I should probably say that I'm getting these readings both 1 inch down, in the rootzone, and at the full depth of the probe, about 6 inches.

That leaves me with grubs and fungus, and neither seem to fit the facts.

Grubs

1 The problem started at about the right time of year for chafers, but early August is on the late side for them, and it's a little early for leatherjackets, from what I've read, and the problem proceeds at pace.

2 No sign of birds or anything else pecking away at the lawn. For some reason they never have, not even for the worms. Wish they would.

3 When I grab a tuft of the dead grass and pull, yes I can pull it out of the ground, but I have to use the same ammount of force as the live grass. It also comes up with roots on. They're dead roots, sparse and spiky, like the dead topgrowth, not fibrous, but they haven't been eaten away just below the surface. Certainly can't just peel the dead turf back as I've read you can do with a grub infestetion.

4 Covered a couple of square feet of combined dead and growing grass with polythene overnight to see if I could sweat anything to the surface. Nothing there next morning.

5 Slipped an edging iron horizontally under the surface to peel back the turf at a couple of places that are just starting to turn yellow. There were no grubs.

6 Notwithstanding all of the above, I've treat it with Provado Grub Killer anyway, and it's still dying at a rate of knots.

So I really can't convince myself that it's a grub problem. Which leaves:

Fungus

1 No visible sign of anything on the blades of grass whilst either growing or dying. No red threads, powdery residue, mycelium (is that the correct word?), nothing. The grass looks perfectly healthy and normal, then it looks straw coloured, then it IS straw.

2 From what I have been able to find out (isn't Google wonderful?) all fungal attacks cause some form of damage to the leaves as the attack progresses. Very close inspection seems to show that my grass is dying from the base up, not the other way round. Yellowing seems to progress up the blade of grass from the bottom, and each blade of grass seems to remain healthy up to the point at which it starts to die, which is not what I expected.

3 Covering part of the lawn with plastic overnight (see above) did not cause the appearance of any fungus-like, cotton-wool like, spiders-web like etc etc growth.

4 My initial thoughts were Dollar Spot. It's fine leaved turf and it has been a wet but warm summer which I understand (thank you again Google) is an ideal scenario for Dollar Spot. (However, there are a few tufts of what looks like Yorkshire Fog and it's killing that too). Furthermore, the affected areas do have a distinct smell, even from a few feet away if you tuned in to it. Not an unpleasant smell, definately not stale urine, but vaguely sort of fungus-like. Well there you are, I hear you say. Why are you writing this?

5 Well, the lawn has been treated with fungicide, twice. It was treated with Bayer "Lawn Disease Control" as soon as the symptoms appeared. I was sure it was Dollar Spot and I had cracked it. It made no difference. If anything it got worse. Two weeks ago I treated it again and the infection continues apace. I didn't necessarily expect it to just stop, my luck doesn't run like that, but I did expect it to at least slow down. Fungicide has had no effect at all.


Now I'm desperate. I can't find any explanation that fits the facts. Two summer's work went into landscaping my front garden and I'm watching it die before my eyes.

Has anyone come across anything like this before?

I should add, south facing, no overhanging trees, no large shrubs in the vicinity to take all the moisture, well drained, no shade.

Just to give you some idea of how fast it's spreading, the area at bottom left in the second picture looked like the bottom right, which is just starting to die off, about 10 days ago, and the area top right looked like bottom left. In two weeks or so pretty much all of the are in the second picture will be dead.

Thanks for sparing me the time to read this.

Tony Allison
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