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Update from the American Phytopathological Meetings


The Midwest is still struggling with heat, humidity and persistent rainfall. As a result, most of the Poa annua in the Midwest is either dead or struggling to say the least. Since I am sitting in the Charlotte airport, I asked Paul Koch for an update on the samples coming into the Turfgrass Diagnostic Lab. It appears that brown patch, Pythium blight and anthracnose are still raging. Our sample numbers are way ahead of last year's entire amount!

It seems that John's post on Monday has caused quite the stir amongst the followers, but he is exactly correct. This is not a "calendar year"! The summer has sucked for most superintendents throughout the US. Grass is dying everywhere and the typical actions like raising the mowing height, alternating mowing and rolling, and other techniques are not helping like we'd like. I think the MOST important thing for golf course superintendents to do is start a line of communication with the owner, membership, golfer, general manager about losing turf. Regardless of the reason or diagnosis this is a banner year for losing turf.

For anyone that knows me I am not a pessimist, but when soil temperatures are above 90 degrees turf is going to have trouble. These temperatures can lead to disease development especially with the amount of rainfall we have had in the Midwest. However, many times grass just dies due to abiotic conditions like poor drainage, anaerobic conditions and heat stress. Remember that annual bluegrass and creeping bentgrass are cool-season grass and prefer to grow when soil temperatures are between 55 and 75 F. Not 90 to 100 F! Lets face it even bermudagrass will struggle when soil temperatures exceed 95 F.

Regarding bacterial wilt, a turfgrass system is a very dynamic biological entity. Many microbes inhabit the rhizosphere of turfgrass plants, which can make turfgrass disease diagnosis extremely difficult. In almost every sample that comes through the TDL, we can find numerous turfgrass pathogens. Furthermore the scientific community is finding that many bacterial species are common epiphytes (live on the surface of leaves) and endophytes (live inside the plant). That being said, it is very common to find bacterial streaming from stressed turfgrass plants. However the signs need to match the symptoms observed in the field and it seems like these two are not jiving.

In my humble opinion, it seems like bacterial wilt has become the perfect fall guy for a brutal summer. It's perfect because it is a mysterious disease with very few effective control measures, but we also have very few control measures for nature.

Summary of a Presentation from APS:

This year's APS meeting was great! Some of the turfgrass pathologist got the opportunity to visit a few golf courses in NC. I was amazed on how quickly I have acclimated to the summers of Wisconsin, damn its hot down there! I really did not have a favorite presentation at this year's meeting. I think the most interesting aspect of the meeting was a special session on Rhizoctonia diseases in turf. There was some fantastic information presented ranging from taxonomic considerations for this genus, biology and management of brown ring patch, management of leaf and sheath spot of ultradwarf bermudagrasses and finally using digital imaging software as a tool to score and identify host resistance in turfgrasses. There was so much information in this session, but the best part was how collegial the speakers were to one another.

Each speaker reference each other and it seemed that they were all working together to help fill in some major gaps with the Rhizoctonia and Rhizoctonia-like diseases in turfgrass. It is cool to be a part of this group, all of my colleagues are extremely helpful and willing to collaborate on projects. As a result, I think we will see many enigmatic problems in turf solved fairly quickly.

13 Responses to “Update from the American Phytopathological Meetings”

hhgcmaint said...

I think you hit the nail on the head with regards to bacterial wilt. It has been a terrible summer, and sometimes the best management practices just aren't going to hold up. There comes a time when we have to tip our hats to mother nature, learn from it, and move on to the next growing season.

Anonymous said...

I agree that mother nature deserves a tip of the hat. However, I'm sure there are legit cases of bacterial wilt. I hope this blog does not shed a negative light on those who are truly battling this problem.

I agree with the blog and hhgcmaint, when it is this crappy out, and we are chemically covered for everything, the turf is going to die of something.

People who are battling this problem, such as myself, can use this as a teaching moment...we don't always have to blame a disease it is okay to blame mother nature. This is just such a case where we can say "we have done everything we can, mother nature is taking them out at a level we cannot compete with."

Lane said...

I don't think anyone is denying that there may be legit cases of bacterial wilt out there on bentgrass. That's why we're working to get to the bottom of it.

My only point is this: you should not accept a diagnosis of bacterial wilt based on the observation of an unknown bacteria under a microscope. Find someone who can isolate and/or identify the bacteria; this is how bacterial diseases are diagnosed. If you don't do this, you will never know if bacterial wilt was the true culprit or not.

Jim said...

Lane is correct, we are not denying the fact that there are legit cases of bacterial wilt. However, most likely to the extent we are hearing. No need to rehash what Lane has said.

John Kaminski said...

I guess I should step in and take some/all of the blame for much of the negativity since posting that the general consensus on BW was BS. That was a generalization about the number of cases being diagnosed and not that the entire thing is BS.

However, I stand by the fact that I don't think that we have a real handle on ANY of the cases and agree with Lane about sending samples in to someone that will isolate and investigate it further.

As the other bloggers pointed out at APS, my comments show the difference between someone from the Northeast and the South or Western US...I can be pretty blunt and harsh!

Brandon said...

I agree with what Lane, Jim, and John said; mainly that John is a direct Northeasterner ;). However, while BW is a legit disease, if you as a superintendent are not working with someone who is going to visit your location, and base the diagnosis both on the samples they take back, and the overall symptoms they observe in person to make a reasoned assessment of what is happening.

When new diseases occur, it is important to remember the lessons of history (think Fusarium Blight aka Necrotic Ring Spot & Summer Patch). Completing Koch's Postulate's is important, and multiple independent examples of Koch's are necessary to really nail down the causal agent. Just because one lab has said that they have run though Koch's, doesn't make it the definitive source. It is possible that they will be finally credited with the discovery of a new disease, but it is critical that this work be repeated.

When a radio telescope (ok-I'm a geek and closet astronomer) thinks they have a new signal that they are receiving from another star there is a protocol that they follow to confirm that it is a legit communication. One of the biggest steps in the confirmation process is to ask another radio telescope to confirm the transmission. This is to make sure that more than one person/group is hearing it. There isn't a worry about getting "scooped" or sharing information, because if indeed it is a legitimate communication from another world, there will certainly be enough fame for the original discoverers to credit the group that confirmed the signal. This should be the case for turfgrass pathologists as well.

Ok, I'm off the soapbox, but folks out in the field, try to remember that football season is getting closer every day, cooler days are ahead (hopefully sooner, rather than later), and we can get into recovery mode. Try to look on the bright side, as hard as this is, we can learn from our recovery efforts how to come back from this kind of stress. This info will be useful in future years because this is not the first difficult year we have had and it won't be our last!

stowell said...

Being a plant pathologist, I am sympathetic to plant pathologist's desire to have a rock-solid diagnosis. The problem is that superintendents need to have an answer in 72 hours to make a management decision. There simply is not sufficient time to figure out what is going on and to complete Koch's postulates. The diagnostician needs to take the best guess and provide likely successful management guidelines.

Last year, I thought we had a bacterial wilt sample arrive at PACE - the field symptoms looked consistent with bacterial wilt. The superintendent followed management recommendations I provided, actually closed the course for a few days, mowed when it was dry, applied chlorothalonil to suppress secondary fungal pathogens, washed off mowers - just in case the problem was bacterial wilt - and used a few products that I did not recommend. The turf finally recovered - but slowly. I worked with Frank Wong and Naveen Hyder at UCR and five months later, we are now pretty sure that the bacteria that I isolated, and the bacteria isolated by Frank and Naveen were not turf pathogens. That still does not prove that some other bacteria or organism was not involved, but the case is pretty strong that the cause of the damage was not bacterial wilt caused by a Xanthomonas or Acidovorax - the more common causes of bacterial wilt. But, the root cause of the damage was probably heat and drought stress.

Although bacterial wilt may be over-diagnosed, we don't have a good answer for superintendents that have submitted samples that are consistent with bacterial wilt. It is a valid diagnosis for the time being. It is the responsibility of the plant pathology research community to aid in figuring out what is going on. But, you can't expect superintendents to wait for the research to be completed. If there is any chance that management targeted at reducing stress to reduce the impact of damage being experienced - those management practices should also suppress the spread of bacterial wilt - why not promote those practices now for locations that are suspect for having bacterial wilt regardless of the final outcome of research on the problem.

One other note, it is not feasible to have a pathologist visit every course that has a disease - there just aren't enough of us. We are going to have to make due with samples shipped to a laboratory. It is an imperfect system that could be improved with more financial support from the industry - more research is needed - we need more funding to support research on bacterial diseases on turfgrasses.

Brandon said...

Larry,
I agree with your assessment that diagnosticians must do what they can with imperfect information and samples of cup cutter plugs. However, the official identification of a pathogen should involve visits, multiple outcomes of Koch's Postulates, etc.

That said, diagnosticians should use a conservative approach when trying to diagnose a potential new location of disease, and they should certainly involve other colleagues to help make sure when dealing with something of this nature that it isn't an artifact. Your example is perfect in this regard: You contacted Frank and Naveen and isolations were made, you made immediate recommendations to try to help the superintendent, and conducted the research as soon as feasible to see if it was a pathogen. This is something that we should think about trying to discuss at a meeting, to try to establish an acceptable protocol that will allow quick diagnostics to occur, while keeping the "cat in the bag" until we have good research-based information. The APS Listserv was created for exactly this purpose.

While we work on turf, there are protocols in other crops to prevent just this type of thing because in other crops widespread diagnosis of a new, potentially dangerous, introduced pathogen (like one on the select agent list) could have a large economic impact especially where it might not actually be occurring.

Anonymous said...

Larry stool my thunder. I get the idea that a field visit is preferable, however, not feasable in most cases.

So many questions then arise. If a field visit is unlikely then what is a superintendent to do? Wait till the diagnotician has a free day...three months later? Particularly when all other diagnosis options have been exhuasted? Some have insinuated that BW is a cop-out. I would suggest the mother nature diagnosis is a cop-out. If one is accepting of "mother nature decline" then how are future managment stratagies to be determined?

To my knowledge the newer generation bents are affected; L-93, the As, Gs, Tyee, etc. Do we then merely reseed to the exisiting grass in the hopes that the same envirnmental conditions do not come back?...because we did not have a field visit? Was this the stratagy during the C-15 decline days?

On the flip side, what do those making the BW diagnosis have to say about the posted criticism? Do they agree with the BS tag? Are they making the diagnosis to help the superintendent get through the tough time?

Lane said...

You don't need to diagnose bacterial wilt left and right to help superintendents right now. I have been out every day looking at greens, and when I haven't been doing that I've been in the lab looking at problems under the microscope.

Earlier this week, Dr. Stowell called for a higher standard in problem diagnosis. I am calling for the same thing. There is no way that you can accurately diagnose bacterial wilt just by seeing some streaming under the microscope, especially not now when we still don't understand which bacteria are most prevalent or what the characteristic symptoms are. It's like a diagnostician calling to tell you that you have 'fungus blight'.

The cause of the problem, whether it be mother nature, bacteria, or something else, is not an academic argument. This is not about blame or cop-outs. This is about identifying the cause of the problem so that it can be fixed and prevented.

So I will say it again: if your greens have been diagnosed with bacterial wilt based on microscopic observation, find someone who will identify the bacteria. This will help us to determine which bacteria are most prevalent and it will help you to develop a program to prevent this from recurring in the future.

Stowell said...

Lane, do you have a list of labs that are capable of identifying bacteria from turf samples. Any idea on price of ID and turn around time? What do they do if the ID finds something new? And, what should they do if the organism can not be cultured on standard media (like rapid blight Labyrinthula) and the lab returns a no pathogen found for the ID.

Maybe the APS working group could come up with a recommended list of management practices for superintendents who think they might have a problem with bacterial wilt. I'm not sure, but I think we could all agree on a treatment regimen that avoids the perils of spraying everything in the chemical shed or dipping mowers in chlorox. I think the protocol would be the first release of a management protocol from the APS working group that deals with such a practical matter. The protocol could be published here with a list of participants to give the recommendations some credibility.

Lane said...

I don't want to volunteer anyone for this duty, but there are labs out there that can do it. Some may only be able to work with superintendents in their state. At NC State, we are routinely identifying bacteria from samples that come into the clinic and show significant bacterial streaming. Right now the turn-around time is slow (a week or more) but as we fine-tune the methods and learn which bacteria are most prevalent it will get faster. Our goal will be to provide an identification in 2-3 days, which is certainly feasible with some of the identification tools out there.

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