Evaluation of Pyrazinamide and Pyrazinoic Acid Analogues for Control of Key Weeds in Multiple Crops

Numerous similarities exist between the structure–activity relationships of pharmaceutical drugs and pesticides, creating the potential for finding new crop management tools with novel mechanisms of action. Analogues of pyrazinamide and its active metabolite pyrazinoic acid were evaluated on a variety of monocot and dicot species to assess their potential as commercial herbicides. Six analogues, applied postemergence at 3 kg ai/ha, controlled yellow nutsedge (Cyperus esculentus) ≥ the commercial standards bentazon or imazethapyr. The compound 5-fluoropyrazine-2-carboxylic acid provided between 71 and 95% control of barnyardgrass (Echinochloa crus-galli) and yellow nutsedge with only modest injury (8–25%) to soybean (Glycine max). A similar compound containing a bromine atom in the 5-position controlled yellow nutsedge greater than bentazon and affected soybean, sweet corn (Zea mays convar. saccharata var. rugosa), and rice (Oryza sativa) in a similar fashion to bentazon as well. The herbicidal sites of action targeted by these analogues of pyrazinamide and pyrazinoic acid are unknown, but it is hypothesized that they may be disrupting targets in the biosynthesis pathways of nicotinamide adenine dinucleotide (NAD) and/or ethylene.