By Sherry Beaty-Sullivan : County Extension Agent, Staff Chair–4-H/Agriculture
Spurweed (lawn burweed, stickerweed, sandbur) is a winter annual and is often confused with sandbur. Spurweed germinates in the early fall months as temperatures cool and remains small or inconspicuous during the cold winter months. Sandbur is a summer weed and resides on poor ground and is not common in the lawn setting. As temperatures warm in the early spring, spurweed initiates a period of rapid growth and begins to form spine-tipped burs. Spurweed can be easily controlled during the winter months. December, January and February are ideal months to apply herbicides for the control. However, the weed can also be effectively controlled in March in most areas of Arkansas. Pre-emerge herbicides that are effective on controlling spurweed are Aatrex (a Restricted Use Herbicide), simazine (Princep, others) and Sencor Turf. This group of herbicides should not be used on bermudagrass over seeded with a cool-season turfgrass or on tall fescue, as they are injurious to cool-season turfgrasses. The best option to control spurweed by homeowners is a post-emergence application of one of the various two and three-way mixes of 2, 4-D, dicamba and MCPP. Trimec is one of the most common trade names in this category. These products can be used on tall fescue, fall over seeded bermudagrass in which the over seeded cool season grass has been mowed four to five times and non-over seeded bermudagrass. This group of products should be applied on a warm (air temperatures at least 55 degrees Fahrenheit), sunny day. Two to three weeks after the initial application, spurweed control should be evaluated. If control is not acceptable, an additional application may be necessary.
The key factor to effectively controlling spurweed is to apply an appropriate herbicide during the winter months. Spurweed 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. Spurweed can be controlled in late-March, April and early May. Spurweed begins to die as late spring temperatures approach 90 degrees Fahrenheit 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 turfgrasses. Once a herbicide has been applied, it takes time for the chemical to react and for the dead spurweed to decompose. Therein lies one of the main problems with late treatments. Dead spurweed plants still contain hardened burs. Dead or alive, the spiny burs still present a problem of late treatments. The only recourse at this point is to allow time for the plant to decompose or to fertilize surrounding grasses to create a greater buffer between the hardened burs and grass canopy. Remember to always read the label before using any chemical on your lawn, many of those suggested in this article will give reduced rates of use for Centipede or St. Augustine grasses. For more information contact the Polk County Extension Office at 479-394-6018 or by email at email@example.com.
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