LAWN BURWEED - IT'S A STICKY PROBLEM

Tim R. Murphy - Extension Weed Scientist

The University of Georgia

The warming of spring days brings about a flurry of spring sports activities such as soccer, softball, baseball, and spring training for football. The players are eager to demonstrate their athletic abilities, the coaches are ready to mold their championship team, but, all of a sudden, players begin to complain about the field. "There's some little weed out there that has stickers on it". The coaches quickly huddle around the "sticky problem" and observe that the field is infested with a spiny, low-growing weed that is annoying the players. The question becomes "What is this weed and how the #!*@ do we get rid of it?"

The weed in question is most commonly lawn burweed (Soliva pterosperma), a.k.a. spurweed, stickerweed, sandbur, sanbur and sandspur. Lawn burweed is a winter annual member of the Aster family. The weed germinates in the early fall months as temperatures cool and remains small or inconspicuous during the cold winter months. However, as temperatures warm in the early spring, or about the same time as spring sports activities, lawn burweed initiates a period of rapid growth and begins to form spine-tipped burs in the leaf axils. The sharp-tipped spiny burs of this weed can cause minor irritation to the skin. Key identification characteristics of lawn burweed are: 1) opposite, sparsely hairy leaves that are divided into numerous segments, or lobes, b) small, inconspicuous flowers, and c) spine tipped burs that are found in the leaf axils (junction of leaf and stem). Lawn burweed attains an overall diameter of up to 6 inches and a height of about 3 to 4 inches. It is commonly found in the Coastal Plain and Piedmont regions of Georgia.

Lawn burweed can be easily controlled during the winter months. December, January and February are ideal months to apply herbicides for the control of this weed. However, the weed can also be effectively controlled in March in most areas of Georgia. On non-overseeded bermudagrass fields, Aatrex (a Restricted Use Herbicide), simazine (Princep, Wynstar, others) and Sencor Turf will effectively control lawn burweed. This group of herbicides should not be used on bermudagrass fields overseeded with a cool-season turfgrass or on tall fescue fields as they are injurious to cool-season turfgrasses.

Other options to control lawn burweed are 2,4-D, dicamba and two-way and three-way mixtures of 2,4-D, 2,4-DP, MCPP and dicamba. Dicamba and the two-way and tree-way mixtures generally provide better lawn burweed control than 2,4-D. These products can be used on tall fescue fields, fall overseeded bermudagrass fields in which the overseeded cool-season grass has been mowed four to five times and non-overseeded bermudagrass fields. This group of products should be applied on a warm (air temperatures at least 55° F.), sunny day. Two to three weeks after the initial application, lawn burweed control should be evaluated. If control is not acceptable, an additional application may be necessary.

The key factor to effectively controlling lawn burweed is to apply an appropriate herbicide during the winter months. Lawn burweed is small and easier to control at this time of the year than in April and May. Also, turfgrasses are not actively-growing during the winter months and have better tolerance to some herbicides. Lawn burweed can be controlled in late-March, April and early May. However, two main facts should be considered. Lawn burweed begins to die as late spring temperatures approach 90° F and the plant is harder to control once the spiny burs or stickers have formed. Multiple herbicide applications are usually necessary, which increases the risk of temporary injury to the turfgrass. Additionally, it takes time for the herbicide to control lawn burweed, and after death, it takes time for the dead lawn burweed plants to decompose. Therein lies one of the main problems with late treatments. Dead lawn burweed plants contain dead, or brown spine-tipped burs. Dead or alive, the spiny burs still present a problem. The only recourse at this point is to allow time for the plant to naturally decompose.