Farmers who don't rely on or want to minimize the use of chemical herbicides need creative solutions to win the battle against aggressive perennial weeds. In ongoing research at the University of Illinois on Canada thistle, Sudangrass is proving to be a worthy contender as a summer smother crop.
"Sudangrass get very tall. It outcompetes the thistle for light. The Sudangrass creates shade so photosynthesis cannot occur in the thistle," said U of I weed scientist John Masiunas.
"In our test plots, primarily in the northern part of Illinois, we've seen 95 percent control, so farmers can plant a cash crop the following year in the patch that had been infected with Canada thistle."
Planting time of the smother crop of Sudangrass is critical, said Masiunas. "It's got to be seeded in the first couple of weeks in June. If you get much past the mid-to late June, the Sudangrass is not able to compete adequately because the thistle grows rapidly in that time period."
A combination of mowing and tilling the thistle before planting the Sudangrass is also recommended.
"Tilling and mowing the thistle interrupts its life cycle so that it can't put energy back into the roots," Masiunas said. Mowing the Sudangrass is important for several reasons. "You can mow to prevent seed heads from forming on the Sudangrass and reseeding itself, and mowing helps to control the amount of residue. If you let the Sudangrass grow the entire season, you'll have a plant seven or eight feet tall, with a lot of shoot tissue, a lot of biomass to deal with. So when you mow it, you just leave it as a surface mulch."
Research on the use of Sudangrass conducted by graduate student Abram Bicksler originated from questions from organic farmers about Canada thistle. "Particularly for sustainable or organic farmers, Canada thistle was becoming very difficult to manage and was becoming the problem weed," Masiunas said.
After Bicksler's project
|Contact: Debra Levey Larson|
University of Illinois College of Agricultural, Consumer and Environmental Sciences