Burke County Extension
Fall Weed Control
Now is the perfect time to control dandelions in your lawn or in the field.
County Agent News
Dan Folske
September 20, 2010
Fall Weed Control
Fall is the perfect time to control perennial weeds, biennials, and winter annuals. Does frost affect control? Maybe. Hard frosts which kill top growth of perennial weeds can prevent the plant from taking in and translocating herbicides into the roots which are the key to perennial weed control. Was last weeks frost hard enough to cause a problem with weed control? Not for the weed patches I’ve looked at. Take a good look at any weeds which you hope to control. By the time you read this severely frost damaged plants should be wilted and/or drying down. If the tops are dead it generally does no good to apply a herbicide. One exception may be Milestone herbicide on Canada Thistle. Research done by Dr. Rod Lym at NDSU has indicated good control of Canada Thistle even when applied very late in the fall with no visible green leaves.
Milestone is not for use in cropland.
Dandelions: Now is the perfect time to control dandelions in your lawn or in the field. Most lawn and ornamental weed killers containing combinations of 2,4-D, dicamba, and/or trimec should be effective this time of year. Glyphosate or Roundup applications are much more effective in the fall than spring.
It may be a little early for fall control of winter annuals. Winter annuals like shepard’s purse, fairy candelabra, and frenchweed or field pennycress sprout and begin growing in late fall and complete their lifecycle early the following spring. Very low rates of 2,4-D or glyphosate are very effective on winter annual seedlings in the fall.
Quackgrass, Canada thistle, and other perennials in cropland may be controlled by post harvest applications of glyphosate but they must be green and growing for any herbicide to be effective. If you have harvested crop by cutting very low to get crop which is lodged or broken down you may have removed too much of the weed growth for herbicide application to be effective unless the plants regrow following harvest.
