Sow-Thistle, Perennial
(Sonchus arvensis L.)

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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 member of the composite or aster family and a very come weed in many of the field crops in Ontario. Perennial sow-thistle was one of the first weeds added to the Noxious Weed List under the Ontario Weed Control Act.

Life Cycle

Perennial , reproducing by seed and from buds on the widely spreading underground root system.

Distinguishing Characteristics

Spiny annual, annual and perennial sow-thistle are often confused with one another. Perennial sow-thistle can be differentiated from sow-thistle as it will be the first to emerge in the spring and will have an extensive underground root system. The leaves of perennial sowthistle are also not as deeply lobed as annual sow-thistle. Spiny annual sow-thistle can be differentiated from annual sow-thistle by its dark green leaves with purplish margins. The leaves of spiny annual sow-thistle also look and feel extremely waxy. Spiny annual sow-thistle is also more "spiny" or "prickly" to the touch versus annual sow-thistle. Lastly, spiny annual sow-thistle has leaves which have rounded basal lobes that clasp around the stem..

Perennial Sow-thistle Pictures
Each thumbnail image links to a larger image

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Herbicide Control in Field Corn

General Control:

Glyphosate applied in the fall to perennial sow-thistle should offer the most effective long term control of this species provided a high enough rate is used and one does not become complacent with respect to yearly management of this weed. Pre-plant glyphosate applications in the spring can also be effective at providing in-season control, provided that the majority of perennial sow-thistle has emerged at the time of application. In general a glyphosate rate of 2 L/ac should provide good control of perennial sow-thistle.

Post Emergent Control

A number of post-emergent broadleaf and "one pass" herbicides should provide supression/control of perennial sow-thistle in field corn (Tables 1 and 2).

Source:

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

Number of Trials:

Table 1 is based on a summary of 2 field trials.
Table 2 is based on a summary of 1 field trial.

Herbicide Rates:

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

Weed Stage:

Perennial sow-thistle was around the 2 to 8 leaf stage 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 Soybeans

A pre-plant application of glyphosate at 2 L/ac will provide good control of perennial sow-thistle that has emerged at the time of application. However since glyphosate has no "residual" activity, it will not control any secondary flushes of this weed. Therefore in "Roundup Ready" soybeans, a second application of glyphosate will be required to control perennial sow-thistle. If growing conventional soybeans, BASAGRAN FORTE (at the highest rate) offers the most consistent level of perennial sow-thistle control, while other herbicides can provide supression (Table 1). CLASSIC, at times, has provided impressive control of perennial sowthistle. However, results have been inconsistent and on average visual control with CLASSIC has been around only 60% (Table 1).

Source:

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

Number of Trials:

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

Herbicide Rates:

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

Weed Stage:

Perennial sow-thistle 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

Refer to Table 8-1 in OMAF Publication 75 - Guide to Weed Control for herbicide ratings on this species.

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.