Marestail: The troublesome weed of Indiana No-till Soybean

Travis Legleiter, Weed Science Professional Assistant, Department of Botany & Plant Pathology, Purdue University

The harsh winter weather of 2014 is bound to break in the coming weeks or month, at least we hope it does. When the snow does melt away, the ground thaws, and the daily temperatures rise, we can be assured that the marestail plants in no-till fields will also begin to grow. This weed is especially troublesome in no-till soybean fields where post-emerge herbicide options are often slim to none.

Marestail is traditionally a winter annual that emerges in the fall, overwinters, and completes its annual growth cycle in the late spring. Although that tradition has been broken by many populations that have shifted to a summer annual growth cycle with emergence dates occurring anywhere from early April through June. The extended emergence range, lack of post emerge herbicide options, and wind blown seeds have made Marestail one of the most troublesome weeds in Indiana no-till soybean fields.

Keys to controlling marestail in a no-till soybean field include a planned and well executed burndown program that controls plants when they are in the seedling or rosette stage, rather than the mature bolting stage. A well-planned burndown program will eliminate all emerged marestail plants prior to soybean planted. The addition of a residual herbicide prior to soybean planting will eliminate any further marestail emergence and allow the crop to prosper without the competition. It will only take a few years of well-executed marestail management programs to significantly reduce the marestail seedbank in a no-till field.

Figure 1. A recently emerged marestail seedling on June 6, 2013 in a no-till field plot at the Southeast Purdue Agriculture Center in Batesville, Indiana.

Figure 2. Uncontrolled bolting marestail plants in a no-till soybean field in southern Indiana.

Figure 2. Uncontrolled bolting marestail plants in a no-till soybean field in southern Indiana.