Fall is an excellent time to control several types of weeds in pastures. Your livestock will appreciate the improvement in palatable forage and the grass plants will appreciate less competition next summer.
Perennial weeds such as field bindweed, thistles, and leafy spurge translocate food from the upper plant parts into the root system in the fall. Herbicides applied at that time readily move into the roots as well, greatly improving the effectiveness of the herbicide. Even if the chemical doesn’t kill the weed, the plant goes into the winter in a weakened condition and is much more susceptible to winter kill.
Fall treatments can be made any time after mid-September but before hard freezes occur. Treatments can even be made after a light frost has occurred as long as the plants are still active and growing. Daytime temperatures in the 50’s are satisfactory for effective control.
Fall is also the best time to control Musk thistle and related species. Musk thistle is a biennial, (sometimes a winter annual), that spreads by seeds. Young plants will have a rosette form that lies nearly flat on the soil. They overwinter in the rosette form and those with sufficient growth, then shoot up (bolt), form blossoms, and go to seed in June, July, and August. After producing seed, the plant dies.
Fall is a good time to control Musk thistle because the newly germinated plants are small and more easily killed. As with the perennial plants, plants not killed outright, go into the winter in a weakened condition and are much more susceptible to winter.
Reduced Drift Potential
In addition to obtaining excellent control on target weeds, the potential for drift damage to non-target species is lessened in the fall. Most field crops and gardens are finished producing be this time, and the current year’s growth on perennial shrubs and trees is hardened off making them less susceptible to damage as well.