A report from the US, but widely applicable I suspect.

https://www.sciencedaily.com/release...1004162019.htm


"Like antibiotic-resistant "superbugs," resistant weeds simply can't be killed by herbicides. There are lots of herbicides on the market, but they all fall into one of 16 categories describing their mode of action (MOA), or specific target in the plant that the chemical attacks. Because of various regulations and biological realities, a smaller number of herbicide MOAs can be used on any given crop and the suite of weeds that goes along with it. At this point, many weeds are now resistant to multiple MOAs.


"In some areas, we're one or two MOAs away from completely losing chemical control for certain weeds. For example, in east central Illinois, we have common waterhemp that is resistant to five out of the six relevant MOAs in a corn-soybean rotation," he says. "And there are no new herbicide MOAs coming out. There haven't been for 30 years."....

"As resources start to dwindle, prices should theoretically go up as a way to prevent overuse and total resource exhaustion. But unlike oil, herbicide prices have actually decreased over the past 30 to 40 years."

Not only that, some manufacturers are boosting the concentration of the active ingredient, so farmers are (perhaps) unwittingly worsening the situation.

I had cause recently to look at the history of Roundup, and Wikipedia supplied the following:


https://en.wikipedia.org/wiki/Glyphosate

"Products are supplied most commonly in formulations of 120, 240, 360,
480, and 680 g/l of active ingredient. The most common formulation in
agriculture is 360 g/l, either alone or with added cationic
surfactants.[64]"

Curiously, Roundup Flex is sold at 480g/l a.i., yet for wiper application, Monsanto still recommends as follows: "Mini 1:3 with water. Other wipers 1:2 with water".

https://www.monsanto-ag.co.uk/media/...ember-2016.pdf

As I remember, this is the same ratio as when Roundup was 240g/l.


JV