Testing for Glyphosate Resistant Canada Fleabane in Tree Fruit, Tree Nuts and Grapes

Kristen Obeid, OMAFRA Weed Specialist – Horticulture

Glyphosate resistant Canada fleabane has been confirmed in 28 counties throughout the province.  Some counties also have multiple resistant Canada fleabane which is resistant to both glyphosate (group 9) and ALS (group 2) herbicides.  It is finding its way from fields of corn, soybeans and wheat into orchards and vineyards at an amazing rate.  Therefore, we need to know what we can do to control and what is there to prevent the further spread of this multiple resistant weed.

If you think you have glyphosate resistant Canada fleabane in your tree fruit, tree nuts or grapes, we will test it for you, using a target-site-resistant (TSR) quick test.

We will send you a sample kit containing instructions on what and how to sample in the orchard or vineyard as well as bags for holding samples and a postage-paid return envelope for the samples.

If you wish to have Canada fleabane tested for resistance, please contact:

Kristen Obeid

kristen.obeid@ontario.ca

519-738-1232 (desk)

519-965-0107 (cell and text)

@WeedProfesh (twitter)

We need leaf tissue from 10 different Canada fleabane plants in your orchard or vineyard.  We then perform analysis on the plants’ DNA using PCR (Polymerase chain reaction) amplification.  Results can be completed within 2 days and then you will know for sure whether or not you have glyphosate resistant Canada fleabane in your fields.  If you do, then we can develop a management strategy to manage this weed.

Canada fleabane (also known as horseweed or marestail) is a winter annual weed. Its seed will germinate either in late summer and over-winter, or in the spring.

Figure 1. Canada fleabane rosette just starting to bolt.  Adequate control will occur at this growth stage or smaller with post-emergence herbicides.

Figure 2. Bolted Canada fleabane.  This is the stage that most plants are at right now.

Effective management strategies should focus on removal of seedling plants both in the fall and in the early part of spring. Since small fleabane plants are not deeply rooted, many different types of tillage implements provide good control of this weed.

Current Registered Herbicides That Provide Good Control of Canada Fleabane

Crop	Pre-Emergence  Spring1	Post-Emergence	Pre-Emergence Fall1
Apple	Alion (G29) Chateau (G14) Sandea (G2) Sencor (G5)	2,4-D (G4) Basagran2 (G6) glyphosate (G9) Gramoxone3 (G22) Ignite (G10) Lontrel (G4) Sandea (G2)	Alion (G29) Chateau (G14) Sandea (G2) Sencor (G5)
Apricots	Alion (G29) Chateau (G14) Sencor (G5)	2,4-D (G4) Basagran2 (G6) glyphosate (G9) Gramoxone3 (G22) Ignite (G10) Lontrel (G4)	Alion (G29) Chateau (G14) Sencor (G5)
Cherries/Plums	Alion (G29) Chateau (G14) Sencor4 (G5)	2,4-D (G4) Basagran2 (G6) glyphosate (G9) Gramoxone3 (G22) Ignite (G10) Lontrel (G4)	Alion (G29) Chateau (G14) Sencor4 (G5)
Grapes	Alion (G29) Chateau (G14)	glyphosate (G9), Gramoxone3 (G22) Ignite (G10)	Alion (G29) Chateau (G14)
Peaches	Alion (G29) Chateau (G14) Sencor (G5)	2,4-D (G4) Basagran2 (G6) glyphosate (G9) Gramoxone3 (G22) Ignite (G10) Lontrel (G4)	Alion (G29) Chateau (G14) Sencor (G5)
Pears	Alion (G29) Chateau (G14) Sencor (G5)	2,4-D (G4) Basagran2 (G6) glyphosate (G9) Gramoxone3 (G22) Ignite (G10)	Alion (G29) Chateau (G14) Sencor (G5)
Tree Nuts	Alion (G29) Chateau (G14) Sandea (G2)	glyphosate (G9) Gramoxone3 (G22) Ignite (G10)	Alion (G29) Chateau (G14) Sandea (G2)

G= Herbicide group

¹ All pre-emergence herbicides can be tank-mixed with glyphosate (G9) or Ignite (G10) or Gramoxone (G22) if Canada fleabane is emerged at time of application.

² Non-bearing trees only

³ Gramoxone (G22) is no longer available for sale, but can be used until December 31, 2018.

⁴ Cherries only.

NOTE: Control of Canada fleabane is best with pre-emergence herbicide applications.  Control with post-emergence applications will always be best on small plants.  Most label rates provide control at less than 20 leaves or 15 centimeters (6 inches), see Figure 1.

NOTE: It is likely that other herbicides in G2, G5 and G14 registered in tree fruit, tree nuts and grapes have efficacy against glyphosate resistant Canada fleabane; however, research trials need to be conducted.

Click here Herbicides for Canada fleabane control for a pdf of the table above.

SPECIAL NOTES:

1. Certain biotypes of Canada fleabane are known to be resistant to ALS herbicides (Group 2). Where these ALS-resistant biotypes are known to exist, an appropriate registered herbicide, active against the weed and with another mode of action, should be used alone or in tank mixtures with SANDEA to control these biotypes.
2. Alion does not have Canada fleabane on the Canadian label; however, it is on the U.S. label.
3. Sencor does not have Canada fleabane on the label; however, many field trials in soybeans suggest adequate control when tank-mixed with glyphosate.
4. 2,4-D and Basagran have Daisy fleabane on the label, but not Canada fleabane.