Control of Poa Annua and Nutsedge

Asked April 16, 2019, 10:43 PM EDT

I have both in my yard. I have a very shady fescue yard that pretty much dies off every summer to where weed control and reseeding every year seems to be the only option. Since I am never too far away from reseeding or having reseeded, I can't use pre-emergent. How aggressively can i attack the nutsedge and poa annua that infests the yard, and should I be doing it anytime it appears, or in the month or so leading up to reseeding? Also, for the ones with seedheads should I bag when I mow, can those reseed themselves, or just mulch clippings like usual? Regards, Chris

Fulton County Georgia

1 Response

Chris,

Selective annual bluegrass control options in fescue lawns are limited. There are a few pre-emergent and post-emergent herbicide options that can be used in the fall and still be able to overseed the fescue lawn. However, resistance to these herbicides is a concern if used too often. Appropriate resistance management strategies should be followed. These products are not available at retail garden centers. They are often sold through commercial landscape supply stores and usually cost prohibitive to the average homeowner. We recommended contracting this work through a commercially licensed pesticide applicator. For more information, see our UGA Extension publications below.

Annual Bluegrass Control Programs for Georgia Lawns:
https://secure.caes.uga.edu/extension/publications/files/pdf/B%201463_2.PDF

Annual Bluegrass Control in Residential Turfgrass:
https://secure.caes.uga.edu/extension/publications/files/pdf/B%201394_1.PDF

Bagging your clippings when seedheads are present can reduce the amount of seeds that will grow back in the fall. Although time consuming, this can help you manage Poa and certain other annual weeds that only grow back from seeds.

Realize that there are a number of other cultural control options that should also be considered to reduce Poa competition. Core aeration to overcome soil compaction problems is critical in the fall each year. Keeping your mowing height a 3" inches is also critical to allowing the turfgrass to out compete Poa and other weeds. Excess moisture or poor drainage also favors Poa invasion over your turfgrass. For example, I have a downspout that drains to my lawn and that's the only spot in my yard that has Poa growing every winter. Maintaining proper soil fertility based on a soil test is also important to increasing the fescue's ability to compete with weeds.

There are retail products available for controlling nutsedge at most garden centers. Products containing bentazon (Basagran and Hi-Yield brands) are labeled for fescue lawns. This product only controls yellow nutsedge species. Bentazon should only be applied to established fescue lawns in the springtime. Do not apply to newly seeded turfgrasses in the fall. Halosulfuron (SedgeHammer) is another product labeled for fescue lawns available at most commercial landscape supply stores.