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Put the pressure on Poa

Weed Control Essentials sponsored by PBI Gordon

Get ahead of Poa annua seedheads before the season even starts.

| February 27, 2014

Handling Poa annua during green-up is a matter of hitting a small window of time perfectly. Shawn Askew, extension specialist and associate professor for Virginia Tech, talks about how to maximize the odds of keeping Poa away this year.

What does a typical Poa annua program look like?

Basically, you’ll take something like Proxy/Primo, normally applied at 50 growing degree days, so one or two mowings after greenup when you’re starting to see seedheads popping up; you would normally spray once with something like that or Embark and then you’re going to come back with another application three to four weeks later. That’s pretty much your seedhead season. Sometimes they’ll split that up into smaller-rate apps and go every one or two weeks.

How would you tackle Poa this year?


I would start with Poa annua seedhead suppression. I’ve been doing some research in this area, and it’s really opened the eyes of the Washington D.C. superintendent group last year. My new concept is that Poa annua, because I can find seedheads for that any time of the year, I believe that on warm days in winter, Poa all over the greens is initiating seeheads. We don’t see them and they may take months to emerge, but they’re there. We’ve monkeyed around and researched for years to find if we could just get the best application. On average, on the first application you’ll get about 40 percent seedhead suppression, and when the second half goes out, you’re clean. But it’s that variability in the first three to four weeks that just drives people nuts.

If we back up to midwinter and dodge snow, if you can put out some early applications that are a month or two prior to the expected season, it should improve seedhead suppression. I’ve done it for four years now, and the difference is night and day. A lot of people, especially in the north, are going to wonder when they’re going to be able to get out and spray in January of February, but occasionally there are years where you can do it.

I’ve recently written a blog post about what I’ve found using this. You can read it HERE.

So which approach is better for control?


Right now we’re looking at a pre-snow or post-snow concept. The question is if you need a pre-snow and post-snow, or just a pre-snow or post. No matter where you are, my data says that if you’re at least a month prior to the normal spring program, post-snow will work fine. But if the snow melts and everything gets warm at exactly that moment, it’s probably not going to do much better because that Poa has started to initiate its seedheads under the snow.

But maybe a pre-snow application in November would be better. What I’m finding in the south where the turf doesn't go dormant maybe until into December, when you’re putting those apps down and you get isolated frost events, you’ll get brown-out. You’ll hasten dormancy. What they’re interested in right now there is dormant sprays. They’re coming out and using Roundup and the concern is: Is my Bermudagrass or zoysiagrass fully dormant? Frankly, there’s no easy way to assess whether or not you’re fully dormant. My rule of thumb is if you can walk on the turf and from a standing position cannot see anything green, it’s dormant.

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