Steve,
I dont think there is any debate on poa getting disease. It does. But so does bent. each get certain diseases more than the other in different regions and climates.
I want to make it clear to anyone following this thread that one size does not fit all. Steve and Jon are in Europe and theyre preaching Nitrogen and its effects with fusarium in poa greens.
Here in Southern California Ive never seen fusarium once. Never at Riviera and never at LACC. And both operations spoon feed the greens aiming at .10 lbs / 1000 of nitrogen on a biweekly basis. Nor has it come up as a serious issue with supers in the entire region.
Steve if we were to generalize and come to a semi-conclusion that if you have a 50 / 50 bent-poa mix and your fert program was down at 2 lbs. N per year and you still end up with that much fusarium.......I wouldnt conclude that it is only because of Nitrogen that causes and promotes fusarium. That amount of disease is unacceptable to me personally and for the clientele I deal with more importantly.
The last time I saw that much disease on a green was at my first job as an assistant super at a nicklaus course in northeast pennsylvania. We had 7 year old greens at the time, totally bentgrass. He also had the fertility down to 2 lbs a year. We constantly had a problem with dollar spot no matter what we sprayed. At one point we were down to a 10 day fungicide spray.....
.....funny thing is that the only thing that saved us was when we bumped up the Nitrogen input.
Also, the picture shows some spreader tracks in the dew. You obviously didnt mow as to try and not spread the mycellium even more and what did you spread on the greens when you woke up to that?
And being at 50 / 50 bent-poa but managing for bent, what are you doing to promote the bent? And is it working?
With promoting bent, are you on any program to kill off the poa chemically? And at what cost? And at what success rate? Is it worth it?
If you are not on any program to eradicate poa, are you not promoting it?
When you started at this course were the greens new 100% bent? If not what was the percentage of poa in the greens?
Im not saying Nitrogen is not a contributing factor to fusarium in your part of the world. How could I? But I do know from my experiences and my colleagues experiences that fusarium hasnt conclusively been attributed to high Nitrogen in my part of the world.
I think Torrey is also a testament to poa greens. The USGA recommended poa greens to a public city owned course for the US Open....
I mowed greens that whole week and was with the USGA officials as they are doing their daily monitering of green speeds and firmness data. The poa conversion from bent was great. And the greens were great. All the poa greens at any US Open have been great. Thats why you see US Open greens as poa. Thats no coincedence. And as far as Torrey, after the US Open is long and gone its still a city course that still has to live with poa greens. If poa was such a monster I dont think a city course on a city budget would want that burden, if it were a burden. Playability-wise and finacially.
I do think we will see our first US Open with bent greens at Olympic though.
Just when I thought we had buried this thread it's back from the dead. I wish my Poa were that resilient.
So many questions.
In my experience, Poa is much more susceptible to diseases than is bentgrass. Not only in my experience, but there is a plethora of documented research saying so.
As bad as the Fusarium is in the photos, it could have been worse. To put it into context, we have two courses, so with practice greens and a nursery I'm managing 40 greens. Six of the greens were affected in that attack, to varying degrees. The photos show the worst damage on the worst affected green. I can only guess how bad it might have been had I pumped the turf up with N. (Another green, not 50 yards from that one, was completely unaffectd.)
The reason I took the photos then was because I was communicating with a pathologist from STRI, Dr. Ruth Mann, who was very helpful. The identification of the disease was never in doubt, but we couldn't figure out what to do about it, it was showing resistance to normal fungicide applications. In the end, I just kept blasting away with the 4-5 available chemicals and it eventually subsided.
The spreader tracks you see in the dew, (very observant, you really are a greenkeeper), was from the application of Scotts Step, a granular micro-nutrient package we were putting down to compensate for a manganese deficiency.
The bad thing is when you get that damage at the end of September, then there's not enough growth for it to recover, and you're looking at the scars until the following May. In this climate, the greens are open year round, except for the odd frost days. They are sand based, I hesitate to say USGA, and they are mowed at 3mm. (0.125 in.) year round as well. Members expect 10-11 feet even in January. Thank God for Primo.
No, I don't expect you will see much Fusarium in Los Angeles. I've noticed that the bentgrass here seems more susceptible to dollar spot than the Poa. But contrary to Fusarium, dollar spot is encouraged by low N, so it makes sense that it would clear up after you bumped the N up in Pennsylvania.
The greens here were already infested with Poa when I arrived, from 10% to 90%, depending. At that time, they were about 10 years old. I don't actively promote either the bent or the Poa. I strive to provide the best playing surface on a day to day basis, and let nature take its course. Research and experience tell me I can't do anything to change the composition of the sward without a critical loss of putting quality for an extended period of time.
What I see is right now, at the end of summer, the greens look about 70% bentgrass, but by next March, they will be predominantly Poa; the dominant population shifts with the seasons.