Will winter annual weeds be an issue this year?
Troublesome Winter Annual Weeds
Two winter annual weeds that are much more troublesome to control and are already showing up as prevalent weeds in Indiana this spring are wild garlic (which is actually a perennial weed) and marestail. Producers encountering these two weed species need to consider management strategies to control populations as early as possible as both species can be difficult to control in advanced plant growth stages.
Wild Garlic has become much more prevalent in agronomic fields this year especially in southern Indiana. Its hollow leaves, underground bulblets, and garlic to onion odor can help identify wild garlic. This weed is not effectively controlled by typical burndown herbicides mentioned above. Wild garlic can be controlled with a thifensulfuron or chlorimuron-containing product that is applied to plants that are less that 12” tall. Further details of wild garlic biology and control will be covered in a near future article.
Marestail will emerge in both the fall and the spring as a low growing rosette and bolt from early spring to summer. Once in the bolting stage and taller than a few inches, marestail is very difficult to control with herbicide applications. Plants that emerged last fall are undoubtedly already beginning to bolt and will be beyond that ideal application stage when soybean burndown applications begin. Producers should consider making early burndown applications to fields infested with marestail as well as including a residual herbicide at a full rate to reduce the amount of marestail emergence prior to and after soybean planting. For more information refer to the “Control of Marestail in No-till Soybean” publication released in collaboration by Ohio State and Purdue Universities. The following link will provide the PDF version of this publication:
While much is to be seen between now and soybean planting, producers need to be aware that winter annual weed control may be more difficult than in past years because of the mild winter and recent warm temperatures. Strategies such as early burndown applications, increased herbicide rates, and the use of residual herbicides need to be considered in order to avoid planting delays and inference that can be caused by winter annual weeds. Producers with a history of SCN infestations also need to be aware of the harboring abilities of certain winter annual weed species. (Refer to Purdue publication WS-36 for more information on winter annuals and soybean cyst nematodes)