Two Noxious Weeds To Control This Fall: Canada Thistle & Musk Thistle
I know many folks are not near it yet, but as harvest winds down, there is another important task that you need to remember. Late October and early November is the best time of year to control two of our most common noxious weeds, Canada thistle and musk thistle.
This is the time of year when these plants build up food reserves in their roots for next year’s growth. Herbicides applied at this time are also translocated to the roots, providing better control than when applied in the spring. Another advantage is many plants that might be injured by drift, but not noxious weeds, may have been killed by a light frost.
You will never get complete control of either of these weeds with a single application, but fall is the best time to start. This may allow you to spot treat individual plants with a herbicide next spring or to cut out musk thistle escapes. It does no good to cut out Canada thistles because they will resprout from the roots.
Even if you do a good job of controlling noxious weeds between a fall and spring treatment, it is important to monitor the areas where they were a problem. The seed may remain viable in the soil for several years.
Canada thistle is the more difficult of these two to control. It may take repeated fall and spring applications. Canada thistle usually is found in patches because it is a perennial and spreads by underground “roots” called rhizomes as well as by seed. When you spray a patch of Canada thistles, be sure to spray 15-20 feet beyond the last plants in the patch you see to get any new shoots just coming up through the grass.
Musk thistle is easier to control because it has a two-year life cycle instead of coming up from roots year after year like Canada thistle. The first year in its life cycle, musk thistles form a rosette that looks like a big prickly dandelion. In the second year, the rosette grows a little more in early spring and then it bolts, or sends up a flower stalk. After it is done flowering and the seed has been produced, the plant dies.
It is best if you control the rosettes in the fall and then treat or cut out any that survived next spring. It is harder to see the rosettes because they may be hidden by the grass. But if you had musk thistles last year, go back to the same areas and look for them. If they were allowed to mature, you may still find some dead flowering stalks to help you identify where rosettes are more likely to be growing. You can treat musk thistles now and into November before the ground freezes.
As it gets later in the fall, your choice of herbicides becomes more limited. Different products are more effective on each of these weeds and even the time of application may make a difference on which product will work best for you.
Controlling noxious weeds is not a pleasant task and may take several years to really see a lot of improvement. However, the sooner you start, the sooner you will see success. So if you have noxious weeds on your farm, this fall would be a great time to start bringing them under control.
For more information on controlling noxious weeds, contact your local Nebraska Extension office or your county weed control superintendent.
