Weeds in pasture and hay fields reduce productivity and the quality of the forage produced. Many times when the weeds are growing in the spring and summer we are either too busy to spray or feel we can’t for a number of other reasons. Fall weed control offers many potential benefits. For example, sensitive crops that might be harmed by drift are dormant and with certain weed control materials clovers can be reestablished the next spring.
Weeds that have great potential for control in a fall program include the plantains (broadleaf types and buckhorn), biennial type thistles, and hairy buttercup. It should be noted that Canada thistle and bulbous buttercup, which are perennials, require a different control strategy than will be discussed in this article. In addition to these weeds, many woody plants such as buckeye and autumn olive can be controlled in the fall with either a basal bark or a cut stump treatment.
Biennial thistles such as bull thistle and plumeless thistle as well as hairy buttercup are effectively controlled with a broadcast application of two (2) pints of 2,4-D plus a sticker (at 0.25% of the total volume of the spray solution) per acre. For spot applications 1.25 ounces of 2,4-D per gallon of water should work well. The plantains can be effectively controlled with 3 to 4 pints of 2,4-D plus sticker per acre. When treating these weeds, it is important that the equipment you use is calibrated and operated properly if you want good control. Factors such as worn nozzles or spraying at the wrong height above the plant can lead to poor results. The weeds need to be growing to get good absorption of the herbicides, so weather also plays a critical role. For good control in the fall or winter you need a period of at least three days of 60-degree weather. You should also never spray immediately before a cold front.
Good control of many woody plants can be achieved with a basal bark application of triclopyr plus an oil carrier such as diesel fuel (75% oil and 25% triclopyr). With this type of application you should wet the bottom 18 inches of the bark of susceptible woody plants with the herbicide solution. For effective control the trunk diameter of the tree or shrub should be no more than four inches. Always follow the label and contact your local Extension office for more information.