Fall Weed Control

Fall Weed Control

October 4, 2021

Control of some of the toughest weeds in your fields is often best done in the fall. Today, we are going to look at some weeds that are traditionally hard to kill, and give some tips for better control.

Canada Fleabane

  • Glyphosate resistant Canada Fleabane is one of biggest problem weeds in Ontario now
  • Majority of seeds germinate from Aug to Nov, forming rosette that is harder to control by the spring
  • Easier to control when Fleabane is smaller

BEST CONTROL SOLUTION: Eragon + Merge, Elevore, dicamba


  • Fall herbicide application is much more effective than spring timing
  • Tillage is effective as long as it uproots entire taproot
    • If taproot is segmented, it will regrow and produce new planT

BEST CONTROL SOLUTION: Glyphosate at high rate (1.34 – 2 L/ac of 540 g/L concentration) is very effective. Lower rate for less than 6” diameter, higher rate for larger dandelion.


  • Summer annuals not generally as big an issue with fall burndowns
    • But Waterhemp has been shown to emerge as late as Sept in Ontario
  • Burndown before seedset in fall can reduce weed seeds going to soil seedbank
  • Blackhawk, dicamba offer good control
  • Part of a season-long program, not enough to control waterhemp with 1 pass

Perennial Sow-Thistle

  • Fall applications will reduce root mass heading into winter
  • Should still expect to see it in following crop
    • But delayed emergence and reduced density
  • Part of program to reduce reserve energy in rhizomes and deplete over multiple seasons

BEST CONTROL SOLUTION: Lontrel, Enlist, dicamba, 2,4-D more effective on larger plant sizes. Glyphosate at high rate (1.34 – 2 L/ac of 540 g/L concentration is very effective as well.

Canada Thistle

  • Uncommon for control of most weeds, fall frost actually benefits control of Canada Thistle
    • Triggers movement of carbohydrates to roots for winter survival, and herbicides can better translocate to the roots
  • Application after the first fall frost drastically increases control for following year

BEST CONTROL SOLUTION: Distinct, dicamba, or Lontrel give effective control

Red Clover

  • Not usually considered a weed, it is a beneficial cover crop that can get out of hand in springtime and make conditions difficult for planting
  • Fall control critical

BEST CONTROL SOLUTION: Glyphosate + dicamba or Distinct is most effective control method

Every field has a different weed spectrum, and some weeds that may be effectively controlled in the fall are not on the list here.

Please contact your Sylvite rep for best practices to manage your field’s weeds! CONTACT US