|Winter damage can be a big problem in Poa.|
So much of the discussion on Facebook and Twitter has shifted to assessing the damage and fixing it. In cases where damage was not observed the focus has been on seedhead suppression. The bottom line for those managing turf in the Northeast, the focus surrounds the suppression and/or management of Poa annua.
|Regardless of whether you want to manage or suppress Poa, you probably feel pretty strongly about your beliefs!|
So over the next two weeks, I will try to provide some insight into what is generally known about managing/suppressing Poa in our region and provide some insight into research that we have initiated to further assess management options.
Here is a list of what is generally known or believed about Poa management:
|Trimmit-treated stand of bent/Poa|
Primo and Trimmit/Cutless are the three most common growth regulators applied to turf during the season. Primo is believed to have little impact on Poa (other than making it stronger), while Trimmit and Cutless have been show to favor the growth of bentgrass over annual bluegrass when used a repeated application program.
There has been no silver bullet herbicide for managing annual bluegrass. Preemergent herbicides effective against Poa are generally not recommended for use on putting green turf. Postemergent herbicides such as Prograss and Velocity have been used with varying results, but again are not labeled for use on putting greens. Various experimental products (cumyluron, methiozolin, others) are currently being evaluated in the United States and have shown great promise. For example, methiozolin is currently labeled for putting green turf in Korea and has excellent efficacy in preliminary studies, but more studies looking at the use of this product are needed.
|Coring can create an ideal Poa seedbed|
This is where we get into the relatively ongoing controversy of management programs. In recent years, there has been a resurgence of programs that involve minimal disturbance (no hollow tine aerification or deep vertical mowing), low nitrogen and phosphorous programs, high ferrous sulfate (and other sulfates) applications, and others. Unfortunately, many of these recommendations are based on "theory" and have not be thoroughly evaluated in controlled research environments.
The general feeling regarding cultural practices for suppressing Poa as I understand it are:
- Low nitrogen will favor the bentgrass over the annual bluegrass and in turn result in less accumulation of organic matter. ADDED CONTENT: (Low P will also favor bent...thanks Dr. Koski for pointing this out)
- Ammonium sulfate as a primary N source will result in acidification and therefore further favor bentgrass.
- Fe, Mg, and Mn sulfate will help in an acidification of the foliage (not sure where this came from) and therefore favor bentgrass AND help to offset color deficiencies in low N programs.
- Core aerification surrounding times when annual bluegrass germination is optimal should in general be avoided. Many of these new Poa management programs dictate that greens be vented often, but that any disruption should be avoided.
- To further help dilute the potential build-up of organic matter, frequent topdressing is generally recommended to encourage the development of a manageable "mat" layer rather than a puffy "thatch" layer.
- I have no idea where this fits into the program, but many seeking to reduce Poa populations are lowering their mowing heights. This seems counter intuitive to me, but that's what I'm seeing and hearing.
- As would be expected, irrigation is minimized to further stress the Poa and favor bent. In this entire program, this one seems like a no-brainer to me and the diligent and thrifty use of water is in general a good idea for limiting Poa as well as associated turf diseases.
- There are probably other things that I have left out, but this post is already getting too long...add your "#8" in the comments or on Facebook.
Next week, I will share some preliminary results of our modified version of the program above which investigates the interaction of nitrogen rates, ferrous sulfate rates, and plant growth regulators on Poa annua populations.