Spurweed—a Lawn Pest that Truly is a ‘Pain’!
Pest Management Guide: Home Grounds and Animals, 2010
Most of the time homeowners view weeds as a nuisance in lawns, but for most, these plants only cause ‘mental anguish’ – not physical. Well, spurweed (also called lawn burrweed) is a lawn pest well known throughout the warmer-climates of the mid-Atlantic for its potential to inflict genuine physical pain to people and pets. Dr. Jeff Derr, Extension Weed Specialist at Virginia Tech, has indicated that spurweed (scientific names of Soliva sessilis or S. pterosperma) is increasing in importance as a serious lawn weed every year throughout Virginia’s Tidewater region, and it has long been noted as a serious pest in the deep south of the United States.
This winter annual broadleaf plant has opposite leaves that are twice divided into very narrow lobes. It looks a lot like parsley in appearance and can be confused with two other lawn weeds that have similar growth patterns and timing: parsley piert and/or knawel. So if you have any questions regarding its identification, you probably want to contact your local extension office for assistance.
Spurweed becomes a major problem in the landscape in mid-late spring when it flowers and sets fruit that are surrounded by razor sharp spines. It is a nuisance to pets, with the sharp spines potentially getting lodged into their paws. And all it will take is one step on this weed by someone walking across the lawn either in bare feet or loose fitting sandals to quickly identify that the weed is present— everyone will know from the shriek of pain! Of course, spurweed on athletic fields is even of more concern for athletes that might be doing a lot of sliding or tackling as part of normal play in spring sports.
There is little that can (or should) be done about spurweed after it has flowered and produced its troublesome spines. If you have it, anticipate it will be producing plenty of seed to support next year's population and make a note on your calendar for the next fall to treat IF you identify it in the turf. Spurweed can be controlled by an application of just about any fall preemergent herbicide in late August to the first week of September (remember that this chemical application will eliminate fall lawn seeding events). From past experience in spurweed control research, I specifically recall that one of the turf industry’s standard PRE herbicides, prodiamine (the active ingredient in Barricade) is particularly weak on spurweed, so if your target weed is specifically spurweed, you will probably need to use additional chemistry. Dr. Derr’s field research trials have shown excellent results in the fall PRE applications of isoxaben, sold as Gallery and Green Light Portrait. This chemical is specific to broadleaf weed control, making it a compatible chemical for most for fall lawn seeding programs. You can also control spurweed quite easily with most two and three-way phenoxy broadleaf herbicides (products containing 2,4-D, dicamba, MCPP or MCPA etc.) if you treat the weed while it is young and actively growing in the fall or early winter.
For commercial applicator use, Dr. Derr has reported the fastest control with Speedzone (2,4-D, mecoprop, dicamba, and carfentrazone-ethyl) and Powerzone (MCPA, mecoprop, dicamba, and carfentrazone-ethyl), although other POST materials such as the standard three-way broadleaf product Trimec Classic and Confront (clopyralid plus triclopyr) also gave excellent control. Princep (simazine) would be another option in bermudagrass turfs where it is labeled for use. There are also other products that will provide acceptable control of spurweed, so carefully research herbicide labels and be sure to follow all directions.
This is one of the pests that causes much more concern than just a disruption of turf uniformity and appearance-- it is a pest that actually inflicts physical pain if not managed appropriately.