Sharpe's Point

Kenny Sharpe

As we transition our lawns into dormancy, it becomes easier to see winter weed problems.

Green plants in an otherwise brown lawn are your first clue that you might be in need of weed control. A good lawn weed control program should start in the winter.

I get several calls in the spring about weeds, but two that come to mind that are preventable now are spurweed (old-fashioned stickers that get in your bare feet) and annual bluegrass.

Spurweed is a winter annual that is germinating right now. It’s so soft that you would be happy to walk on it barefooted. It usually starts germinating in December and then grows all winter long until it flowers around April 15. When it flowers, it forms spines and reseeds itself for the next year — so no more walking on it without shoes. I get many calls in April about controlling it, but by then it is too late.

Annual bluegrass — also known as Poa annua — is coming out now also. It looks like a winter grass. It grows in small clumps and will quickly put out a white seed head. When you cut annual bluegrass in the spring, it refuses to be cut neatly and will look like little wires dangling above the grass canopy in all directions.

In addition to these, dollar weed and Dichondra (pony’s foot) are also present now. I am also seeing clover and Carolina geranium, and buttercup is already flowering in some areas.

The old notion that “an ounce of prevention is worth a pound of cure” would apply here. There are two herbicides that are pre-emerge chemicals that also have post-emergence activity on these young seedlings that would work well. Those herbicides are atrazine and simazine.

These herbicides will work well in cold weather. They will prevent any seeds that have not already germinated from emerging while also killing off small seedlings that have already germinated and emerged.

You can enhance the activity of simazine and atrazine by adding a 2,4-D blend such as Bayer Advanced Garden Southern Weed Killer, Green Light Wipe Out, Trimec, Fertilome’s Weed Free Zone and Ortho Weed B Gon.

If you use the 2,4-D blends either alone or as a tank mix, you’ll get the best results when the temperature is at least 65˚F in addition to bright sunny weather. Also make sure to spray on a calm day as 2,4-D tends to drift in the wind and can affect off target plants.

For livestock producers, hay supplies are very limited. Too many rainy days for many producers to put up hay. It will be very important to utilize ryegrass efficiently. One way to help is to control buttercup in ryegrass early so it does not take up space and nutrients in your cool season pasture.

In one study that we conducted in Baton Rouge, we sprayed ryegrass that was infested with buttercup with 1 pint of 2,4-D per acre between mid-December and January and got control of 92 percent. When we delayed treatment until March, our control was less than 70 percent. In addition, 1 pint of 2,4-D per acre will not kill white clover. All over clovers are very sensitive to 2,4-D and will be killed by even this low rate of 2,4-D.

Since buttercup is an annual weed, it is important to spray before it flowers to reduce the seed load for next year. Even then, you may have to spray several years before you deplete the seed load that is already in the soil.

For more information on these or related topics, contact Kenny at (225) 686-3020 or visit our website at www.lsuagcenter.com/livingston.

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