42
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Safety - page 25 • First aid - page 33 • Resistance management - page 41
Herbicides
How to minimize the development
of resistance
Follow the guidelines below to delay the appearance
of resistance:
•
Integrated weed management practices –
use herbicides as part of an integrated control
program that includes scouting, historical
information related to herbicide use and crop
rotation, and consider mechanical, cultural,
biological and other control practices.
•
Herbicide and crop rotations – herbicides
must be rotated. It is important not only to use a
different herbicide, but to use one from a different
herbicide group with a different mode of action.
•
Field history – records are needed to make
sensible decisions on herbicide rotation and to
evaluate the probability of resistance developing.
A pesticide application record sheet can be found
at the back of this book.
•
Tank mixture – a tank mix may delay the
appearance of resistant weeds if the components
of the tank mixture control the same weed by a
different mode of action.
•
Monitor results – Monitor treated weed
populations for resistance development.
•
Preventive measures – prevent the movement
of resistant weed seeds to other fields by cleaning
harvesting and tillage equipment as well as
planting clean seed.
Herbicide Resistant Weeds in Alberta
Herbicide group
Weeds
Group 1
Green foxtail, wild oats
Group 2
Ball mustard, chickweed, cleavers, hemp-nettle, kochia*, Russian thistle,
spiny annual sow thistle, stinkweed, wild mustard, wild oats
Group 3
Green foxtail
Group 4
Hemp-nettle
Group 8
Wild oats
Group 1 + 2 + 25 (multiple resistance)
Wild oats
Group 1 + 2 + 8 + 25 (multiple resistance)
Wild oats
Group 1 + 3 (multiple resistance)
Green foxtail
Group 2 + 4 (multiple resistance)
Cleavers
Group 9
Kochia
•
NOTE: There is now a confirmed case of gylphosate resistance(Group 9) in kochia in Southern Alberta. Other cases of
glyphosate resistance have been reported in Ontario with giant ragweed and Canada fleabane.
•
Surveys of prairie kochia fields have found that approximately 90 per cent have Group 2 herbicide resistance. Without
testing assume kochia found in Alberta is resistant as well and needs to be controlled with herbicides from a different
herbicide group.
Herbicide resistance screening on suspect weeds can be performed by the Saskatchewan Crop Protection Lab
(306-787-8130)
for a fee, ranging from $35 to $100 per sample. Or contact the chemical company or the
Alberta Ag-Info Centre toll-free at 310-FARM (3276).