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Red Leaf Spot Active...

Disease activity has basically gotten to a point of boredom for many of us who like to see new and exciting diseases. Dollar spot continues to be the number one problem in the Northeastern United States and this is not much of a departure from the past few weeks or so. Temperatures are finally getting cooler at night, but the forecast for some areas have temperatures reaching into the 80's again this week.

Much of the effort in terms of turfgrass management has shifted towards the necessary cultural practices needed to ensure healthy turf heading into the winter and also coming out of spring. Snow mold applications are still a couple of months away, but superintendents would be wise to check out some of the posts from Dr. Kerns in the Midwest region where he experiences some of the highest snow mold pressures around.

For me, last week was fairly exciting (although not exciting enough to come up with another PlayTurf cover) as some of our plots unexpectedly developed red leaf spot. While at Maryland, we heard a lot of buzz from superintendents in the field who felt that they were dealing with red leaf spot. However, upon further inspection we almost always found the disease to be late cases of Microdochium patch (aka, Pink snow mold or Fusarium patch) occuring during overcast weather. This caused some controversy to the point of almost having a manuscript rejected because the editors suggested that we did not probably identify Microdochium patch (the disease was rated in the first week of June in Maryland...which was highly unusual). I assured the editors that I was a major advocate of the cereal Lucky Charms and could easily distinguish my "crescent moon shapes" (typical of Microdochium) from that of a cigar (typical shape of the Dreschlera genus that causes red leaf spot).

Anyway, the real first time that I even saw red leaf spot was at the research plots at my first University of Massachusetts field day. I took out the trusty pocket knife and took a small sample back to the lab at UConn and sure leaf spot (sorry for whose ever plots those were...I only took a small piece). In reviewing the latest turfgrass fungicide updates from the University of Kentucky, the reports from Paul Vincelli generally hold true with the data collected from the unexpected disease in our plots. Our data suggest that the QoI fungicides held up equally well (Disarm did seem to provide slightly less control, but this was not significant). Although ProStar did not enhance disease activity in our plots as suggested by Dr. Vincelli, it definitely did not provide any suppression. Two surprises in the data relative to past trials were that myclobutanil (Quali-Pro) seemed to provide excellent preventive suppression AND that Emerald (which is only good for dollar spot and bentgrass dead spot) seemed to provide a moderate level of suppression of the disease.

Since this is my first time seeing data on red leaf spot in my own plots, please feel free to comment on your thoughts about the disease in trials conducted in your region. As with Jim's post last week about the lack of control with Curalan for early season dollar spot, we may continue to see differences in control of certain diseases based on these geographic regions.

4 Responses to “Red Leaf Spot Active...”

jdempsey said...

I receive feeds from your site for the last while, which I must say I find very interesting, I have to say the range of diseases you guys deal with is magnificent! I’m a golf course manager in Ireland John Dempsey is my name and over here we have really only a couple of major fungal problems –Microdochium patch, and Anthracnose being the two which cause most damage, we also have to a smaller extent occasional problems with Yellow tuft (Schlerathora macrospora) Take all (Gaeumannomyces graminis)and Pythium. Our weather is always very temperate and damp! Usually our disease problems are regular as clockwork –we control Microdochium from October to March and Anthracnose from July to end of August, although the last three summers have been wetter than the average and Microdochium pressure has been evident throughout the year. Snow molds are not a problem as if we get snow it’s only a couple of cm or inches as you would say! and it only lasts a few days at most.
Here’s a question for you, I’m looking for data, preferably from primary scientific refereed papers, which determines the precise mode of infection of Microdochium, that is how it firstly enters the plant, is it by way of the stomata, intercellularly or by appressoria formation and then into the plant? After that then I’m interested in the defence responses and processes initiated by turfgrass once the pathogen has gained entry into the plant. So looking forward to your responses and if you have any questions regarding golf course management and disease problems here in Ireland I will be glad to help.

John Kaminski said...


Sounds like you may have to bring us over for a field trip to check out the diseases. Lane and I were there in April of this year and would be happy to get back anytime!

I will look into those references and get back to you.

Thanks for the comments.


Jim said...

I would love to be a part of that trip too :)

As far as the references, if you find anything please let us know. As far as I can tell, we do not know this information for turf.

They have a pretty good idea in wheat, but not turf.


jdempsey said...

Thanks for getting back, if youre over this way let me know and I'll give you all a tour of the Curragh golf course here, its the oldest in Ireland golf here since 1852.

With regard to the Microdochium info, it is part of a a research proposal I'm preparing for a PhD, studying the implications of phosphite and silica treatments on turfgrass and how they may stimulate defence response such as phytoalexin production.

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