Bill Starr: Warmer temperatures bring out bare feet; beware!

Published 4:00 pm Tuesday, April 19, 2016

The warm weather of spring days brings about a host of sports activities such as soccer, softball, Frisbee, and my personal favorite — spring football. With all the activity in the yard or sports field participants soon discover that all is not well with the turf. They soon discover that there is a “sticky” problem and find their yard is infested with a spiny low-growing weed that is annoying to deal with. With the numerous calls I have been receiving about this weed I am sure a lot of you are familiar with it.
The weed is question is most commonly called lawn bur weed (soliva pterosperma) The Latin meaning of this weed is winged seed, the English translation is “Oh (input word of choice ); I just stepped on that.” Other names for this weed include spur weed, sticker weed, sandspur and maybe many others I haven’t heard. Lawn bur weed is a winter annual member of the Aster family. The weed germinates in the early fall months as temperatures start to cool down and remains small and inconspicuous during the cold winter months. However now that warmer temperatures are upon us lawn bur weed initiates a period of rapid growth, and begins to form spine-tipped burs in the leaf axils. This year we seem to have a bumper crop of this weed.
The key factor to effectively controlling lawn bur weed is to apply a post emergence herbicide during the winter months of December, January and February. The weed is smaller and easier to control during this time of year and has not yet developed the spine-tipped burs. Control is not impossible in March, April, and May, but the spines have already formed by this time and will remain after the weed dies. Because lawn bur weed is a winter annual, it will begin to die in late spring as air temperatures reach 90 degrees F. Once the weed has reached a more mature state, multiple herbicide applications may be necessary which increases the potential for turf grass injury.
Dead or alive, lawn bur weed poses a painful problem. The only solution to this is early identification and control. A three-way herbicide may be used on Bermuda grass, zoysia grass, centipede grass,  and St. Augustine grass  The active ingredients of a three-way herbicide typically include the following three broadleaf weed killers: 2,4-D, dicamba, and mecoprop (MCPP). Products that contain a higher percentage of dicamba and mecoprop will more effectively control lawn bur weed, than 2, 4-D alone.
Herbicides containing 2, 4-D should be applied at a reduced rate on St. Augustine grass and centipede grass to prevent damage to these lawns. If a second application is needed, apply the herbicide in spot treatments. Repeated applications of a three-way herbicide should be spaced according to label directions. Read the label for the rate to use on each turf grass species. In addition to three-way herbicides, there are several other herbicides that can be used for lawn bur weed control in home lawns. Atrazine may be used for weed control in centipede grass and St. Augustine grass. Atrazine applied in November will have post-emergence activity against newly sprouted lawn bur weed seedlings and also will have pre emergence activity against those that have not yet germinated during the fall.
Remember that herbicides take time to control weeds, and after it dies it takes time for lawn bur weed to decompose. That is one of the main problems with late treatments; dead lawn bur weed contains the spines that hang around for a while. Dead or alive bur weed can still present a problem. The only thing you can do at this point is to allow time for the weed to naturally decompose. Sort of limits barefoot activities until it’s all gone. It seems this year more people have become familiar with this weed than in years past. I hope this “sticky” problem doesn’t continue.

Bill Starr is Sumter County Extension coordinator and AN agent, University of Georgia Cooperative Extension Service. Contact him at 229-924-4476.