Resistance is a complex topic and to make generalizations is dangerous. Get
into disease resistance and it's even more complicated. We farmers can't
even begin to understand it. It like talking genetics, after a very short
time its just words - big ones!
There are 2 main types of weed resistance, enhanced metabolism and target
site.
Enhanced metabolism. This causes more rapid herbicide detoxification
within resistant plants. Resistance tends to be partial but plants may be
cross resistant to a wide range of herbicides with different modes of
action. This form of resistance tends to develop quite slowly over a period
of years. Roundup falls in this category.
Target site resistance. This blocks the site of activity specific to the
herbicide’s mode of action. This usually results in complete resistance to
herbicides acting on that specific site, but not to herbicides acting on
different targets. Two main types have been identified: one affects ‘fop’
and ‘dim’ graminicides (ACCase inhibitors) - Group 1; the other affects
sulfonylurea herbicides (ALS inhibitors) - Group 2. Resistant populations
can increase rapidy.
This post is about Group 1 target site resistance and is what I was
referring to.
A good read:
http://www.umanitoba.ca/outreach/naturalagriculture/weed/files/herbicide/re
duced_rates_e.htm
If a wild oat biotype is resistant, it can easily take 40 times the rate to
kill it as there is no target site in the plant for the ACCase herbicide to
do its job. That's when you hope the liberty is getting it.
into disease resistance and it's even more complicated. We farmers can't
even begin to understand it. It like talking genetics, after a very short
time its just words - big ones!
There are 2 main types of weed resistance, enhanced metabolism and target
site.
Enhanced metabolism. This causes more rapid herbicide detoxification
within resistant plants. Resistance tends to be partial but plants may be
cross resistant to a wide range of herbicides with different modes of
action. This form of resistance tends to develop quite slowly over a period
of years. Roundup falls in this category.
Target site resistance. This blocks the site of activity specific to the
herbicide’s mode of action. This usually results in complete resistance to
herbicides acting on that specific site, but not to herbicides acting on
different targets. Two main types have been identified: one affects ‘fop’
and ‘dim’ graminicides (ACCase inhibitors) - Group 1; the other affects
sulfonylurea herbicides (ALS inhibitors) - Group 2. Resistant populations
can increase rapidy.
This post is about Group 1 target site resistance and is what I was
referring to.
A good read:
http://www.umanitoba.ca/outreach/naturalagriculture/weed/files/herbicide/re
duced_rates_e.htm
If a wild oat biotype is resistant, it can easily take 40 times the rate to
kill it as there is no target site in the plant for the ACCase herbicide to
do its job. That's when you hope the liberty is getting it.
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