Dear Expert - This year I have experienced a significant amount of what appears to be orchardgrass growing in certain areas of my yard where the fescue lawn was under stress. See attached photos. I started to pull it out, but quickly realized I can't keep up with its growth. What is the most effective and most economical spray chemical for a post emergent control? I also have a Dallisgrass growing in my lawn, and I was wondering if the same herbicide would kill it. Note: Weed-B-Gone Plus Crabgrass Control (2 oz. per gallon) does not seem to have any impact these grassy weeds. Will M.
This very much looks like a weed called Poa trivialis or roughstalk bluegrass. Poa trivialis is a perennial grass, which spreads by stolons and seed. It cannot, therefore, be controlled with an herbicide labeled for crabgrass which is an annual grass.
The best way to control Poa trivialis is to use a systemic herbicide, namely one containing the ingredient glyphosate. Glyphosate can be found in many products, but originally only in Round-Up. This will leave dead patches that will have to be reseeded.
Please see the following information from our website, http://extension.umd.edu/hgic/topics/roughstalk-bluegrass
Unfortunately, the same can be said for dallisgrass. The active ingredient in the herbicide that was used to control it was taken off the market many years ago.