Fleabane, Canada (Conyza canadensis)

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Table of Contents

1. History
2. Life Cycle
3. Distinguishing Characteristics
4. Control in Corn
5. Control in Soybeans
6. Control in Winter Wheat

History

A weed species that thrives under cool damp conditions and little soil disturbance. Canada fleabane is typically found in no-till production. It has recently become a weed of interest after glyphosate resistant populations were discovered in 9 American States.

Life Cycle

Annual or winter annual reproducing only by seed. Preliminary reseach by Francois Tardif has shown that Canada fleabane will germinate throughout the year if not shaded by a crop canopy. Peak flowering of Canada fleabane will occur in early summer to late autumn.

Distinguishing Characteristics

A very hairy weed species that can reach heights of up to 1.5 metres. The leaves are dark green in colour, linear and lanceolate with many small hairs. The lower leaves will have toothed margins whereas the upper leaves will tend to have smooth margins. Canada fleabane has numerous small white flowerheads that appear very "fluffy" at maturity. Allegedly, Canada fleabane will also exude a "carrot-like" odour.

Canada Fleabane Pictures
Each thumbnail image links to a larger image

Herbicide Control in Field Corn

Tillage or a pre-plant burndown will provide season long control of Canada fleabane assuming that the crop canopy closes quickly. In fields with high fleabane populations or multiple emergence flushes, it may be advantageous to include a residual herbicide with a glyphosate burndown (Table 1) or follow up the pre-plant burndown with a post-emergent herbicide (Table 2).

Source:

Dr. Peter Sikkema, Ridgetown College, University of Guelph.

Number of Trials:

Tables 1 and 2 are based on a summary of 1 field trial in corn.

Herbicide Rates:
Rates used in this trial are listed in OMAF Publication 75 - Guide to Weed Control.

Weed Stage:
Canada fleabane was at the 2 to 16 leaf stage (1 to 9 cm in height) at the time of all pre-emergent applications (Table 1). Canada fleabane was at the cotyledon to 20+ leaf stage (1 to 28 cm in height) at the time of all post-emergent applications (Table 2).

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Herbicide Control in Soybeans

Pre-Plant and Pre-Emergent Control

Tillage will control this species in conventionally tilled systems. A pre-plant burndown is required in no-till crop production. In general, glyphosate provides the best pre-plant control of Canada fleabane (Table 1). However, amongst concerns of glyphosate resistance, products like Amitrol 240 and FirstRate would be cost-effective alternatives.

Post-Emergent Control

A pre-plant application should provide season long control of Canada fleabane provided the soybean crop canopies quickly to inhibit new seedling germination. If secondary germination produces new seedlings after pre-plant herbicide applications, post-emergent herbicides such as glyphosate (in Roundup Ready soybean only), Classic and FirstRate will provide good post-emergent control (Table 2).

Source:

Dr. François Tardif and Dr. Peter Sikkema, University of Guelph.

Number of Trials:

Tables 1 and 2 are based on a summary of 3 field trials in soybean.

Herbicide Rates:
Rates used in this trial are listed in OMAF Publication 75 - Guide to Weed Control.

Weed Stage:
Canada fleabane was at the cotyledon to 20 leaf stage (2 to 10cm in height) at the time of application.

What has been your experience?
We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

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Herbicide Control in Winter Wheat

Post-Emergent Control

With the exception of MCPA Amine, Refine Extra and Buctril M, Badge or Mextrol, most of the post-emergent broadleaf herbicides registered for use on winter wheat provide good control of Canada fleabane (Table 1).

Source:

Dr. Peter Sikkema, University of Guelph.

Number of Trials:

Table 1 is based on a summary of 3 field trials in winter wheat.

Herbicide Rates:
Rates used in this trial are listed in OMAF Publication 75 - Guide to Weed Control.

Weed Stage:
Canada fleabane was at the 3 to 6 leaf stage (0.5 to 3 cm in height) at the time of application.

What has been your experience?
We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.