Results: Fall Application Survey

Each year Techline receives questions from readers about treating broadleaf perennial weeds in the fall—including whether it is an effective application timing, what weeds are most susceptible to fall herbicide treatments and WHY?
We asked our readers to answer three questions about their perceptions regarding advantages and disadvantages of applying herbicides in the fall. Responses to the questions were summarized and shown below each question.  

1. Agree or disagree? Fall is a good time to apply herbicides for perennial weed control.

[Respondents were asked which of the following options best reflected their opinion of the statement above:  1) strongly agree; 2) agree; 3) disagree; or 4) strongly disagree].

2. In your opinion, why is fall herbicide application timing effective or not effective on perennial weeds?

[Responses from those who agree or strongly agree]

*EDITOR'S NOTE: Safety to non-target plants was described as a reason why an applicator may choose to apply herbicides in fall. To better understand the susceptibility of some desirable forbs (wildflowers) to spring/fall herbicide application go to  


[From those who indicated that they strongly disagree (1 response)]:

  • Plants absorb into the roots everything that is within the plant above ground


3. Based on your experience or knowledge of published information, which invasive plant species are good targets for fall herbicide application?  

[The first 4 bullets were listed by the greatest number of respondents.]
  • Canada thistle
  • Woody plants: Ailanthus [tree-of-heaven], honeysuckle, autumn olive, black locust, salt cedar, glossy buckthorn
  • Biennial/short lived perennial plants (fall rosettes): thistles (bull, musk), burdock, houndstongue, dames rocket
  • Knapweeds (spotted, diffuse, Russian)
  • Leafy spurge
  • Rusk skeletonweed
  • Invasive knotweeds
  • Garlic mustard
  • Absinth wormwood
  • Field Bindweed
  • Narrowleaf cattail
  • Parsnip
  • Phragmites
  • St Johnswort
  • Sulfur cinquefoil
  • Common tansy
  • Yellow toadflax
  • Winter annuals

Other comments:

  • Typically, species that are rhizomatous or otherwise have large root masses (giant knotweeds; field bindweed).