There is no such thing as "herbicides" they are semi targeted biocides and are not maintaing there effectivness or targeted enough to prevent unacceptable "collateral" damage. Biology supports this as there are very few parallels to be found in nature for this kind of defence/offencive use of chemicals in multi cellular life.Which is a great big hint as to the true cost benifit equation over, reproductive time scales Many single celled life does of course use chemical deffensive/offensive products, yeast and various algae capable of powerfull effects on many life forms. Then there are venoms,but those are mechanicaly targeted. Nature evrn invented the "tazzer" as a weapon/deffence,in electric eals. Ignoring the vast and tested data set that is present in nature is dumb.