Ohio State University weed scientists have discovered another herbicide-resistant weed, making it the eighth confirmed weed species in the state that has gotten the upper hand on chemicals.

Smooth pigweed shows resistance to aceto-lactase synthase-inhibitor herbicides, also called ALS-inhibitors. This herbicide group kills weeds by preventing plants from producing essential amino acids needed for growth and development.

Other Ohio ALS-resistant weeds are shatter cane, giant ragweed, common ragweed, marestail, Powell amaranth, common cocklebur and waterhemp.