Herbicide resistant weed testing: University of Guelph lab results

Written By: Kristen Callow, OMAF and MRA Weed Management Program Lead – Horticulture

Source: Dr. F. Tardif and Peter Smith, University of Guelph

Adapted from: http://fieldcropnews.com/2013/04/herbicide-resistant-weed-testing-university-of-guelph-lab-results-2013/

Below is a summary of some of the weed samples sent into the University of Guelph by producers and agronomists that suspected resistance to a particular herbicide during the 2012 season. Also included are herbicide options with different modes of action that are effective on each species in horticulture crops.

Common Lamb’s-quarters

14 samples tested from 2012 fields

Common Lamb's-quarters Resistance
Common Lamb’s-quarters Resistance

Alternative Solutions in Potatoes: Chateau – Western Canada only (PRE); Eptam (PPI); Lorox (PRE); and  Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and alternatively if you only have Group 5 resistance you can apply Prism.

Alternative Solutions in Tomatoes: Treflan, Rival, Bonanza (PPI); Devrinol (PPI); and Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and alternatively if you only have Group 5 resistance you can apply Prism.

Pigweed Species

26 samples tested from 2012 fields

Pigweed Resistance
Pigweed Resistance

Alternate Solutions in Carrots: Treflan, Rival, Bonanza (PPI) – not on soil with > 15% organic matter; Dual II Magnum (POST); and Aim with a hooded sprayer between rows (POST).  There are other products in the registration system: https://onvegetables.com/2013/04/12/management-strategies-to-control-resistant-pigweed-in-carrot-production/

Alternate Solutions in Potatoes: Chateau – Western Canada only (PRE); Eptam (PPI); and Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and Lorox; if you only have Group 5 resistance you can apply Prism and Lorox and if you only have Group 7 resistance you can apply Prism and Sencor.

Alternate Solutions in Tomatoes: Treflan, Rival, Bonanza (PPI); Devrinol (PPI); Dual II Magnum (PPI); and Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and alternatively if you only have Group 5 resistance you can apply Prism.

Common Ragweed

34 samples tested from 2012 fields

Ragweed Resistance
Ragweed Resistance

Please note: the majority of these samples came from Quebec carrot fields.

Alternate Solutions in Carrots:  Aim with a hooded sprayer between rows (POST).  There are other products in the registration system: https://onvegetables.com/2013/04/12/management-strategies-to-control-resistant-pigweed-in-carrot-production/.  If you only have Group 7 resistance, you can apply Gesagard and alternatively if you only have Group 5 resistance, you can apply Lorox.

Alternate Solutions in Potatoes: Chateau – Western Canada only (PRE); and Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and Lorox, if you only have Group 5 resistance you can apply Prism and Lorox, and if you only have Group 7 resistance you can still apply Sencor and Prism.

Alternate Solutions in Tomatoes: Aim with a hooded sprayer between rows (POST).  If you only have Group 2 resistance you can apply Sencor and alternatively if you only have Group 5 resistance you can apply Prism.

Remember, once you have a resistant weed on your farm, it is there to stay.  For example, pigweed can produce on average 100,000 seeds per plant and can remain in the soil for close to 40 years.  It is best to use a combination of management techniques (integrated weed management) to help minimize the resistant seed return to the soil each year including: crop rotation, shallow tillage to minimize bringing weed seeds to the soil surface, removing weeds from the field before they set seed, and cleaning all equipment thoroughly before entering another field.

Resources:

www.weedinfo.ca

http://www.plant.uoguelph.ca/resistant-weeds/

www.omafra.gov.on.ca/english/crops/pub75/pub75.pdf

http://pr-rp.hc-sc.gc.ca/ls-re/index-eng.php

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