Solvia pterosperma, Lawn Burweed
Don’t wait too late to control winter annual lawn weeds. It’s time to use a preemergence herbicide to control winter annual weeds if your lawn has a history of problems with these weeds. Otherwise, you might want to save your money.
Common winter annual weeds include annual bluegrass (Poa annua), chickweed, henbit, hop clover, lawn burweed and wild geranium.
Timing of herbicide applications is of utmost importance in controlling winter weeds that are about to sprout in home lawns all over North Florida. If you intend to use a preemergence herbicide, you’ll need to apply it during the month of October when nighttime temperatures drop to 55 to 60 degrees for several consecutive nights. This will be just before the winter annual weeds emerge. With the recent cooler night temperatures, you need to act quickly if you intend to use a preemergence weed control in your lawn.
Some preemergence herbicides to look for include oryzalin (Surflan), benefin (Sta-green Crabgrass Preventer, Hi-Yield Crabgrass Preventer), pendimethalin (Pre-M, Pendulum, Turf Weedgrass Control, Scott’s Halts), benefin + oryzalin (XL) and DCPA (Dacthal). There are others – check with local garden supply stores. I’ll forewarn you that many of these products are better available in spring and may be difficult to find in fall. This is partly because they are marketed more for summer annual lawn weeds. And when the stock is sold out, many stores do not reorder for fall, not realizing the use of these products for winter annual weed control.
For season-long weed control, a second application might be needed about nine weeks after the initial application. To acivate some products, irrigation or rain might be necessary following application.
Not every lawn needs an application of preemergence herbicide this time of year. If your lawn has had no problem with winter annual weeds, there’s probably no need to apply a preemergence herbicide to prevent non-existent seedlings from emerging.
Always follow all label directions and precautions when using any pesticide. Use preemergence herbicides only on lawns that have been established for at least a year. They can severely injure freshly seeded or sprigged turf grass. Many preemergence products interfere with lawn grass seed germination, delay reseeding 6 to 16 weeks after application. This applies to over-seeding a lawn with rye grass seed.
For additional information on winter weed control, contact your local UF/IFAS County Extension Office or visit http://edis.ifas.ufl.edu/EP141 .