My sign is when normal glyphosate formulations at either a 1% solution directed spray or 2 quart per acre broadcast does not effect a complete kill. I do not look for a more concentrated glyphosate or a richer mix. Alternative herbicides are used in that situation
RoundUp tolerant weeds can cost me a lot of money if I do not handle them correctly. Using the alternative herbicides at their typical low usage rates often costs less in time and materials than a failed RoundUp application.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738