Bioherbicidal activity of Sinapis alba seed meal extracts

Although seed meal from yellow mustard (Sinapis alba L.) is a potential tool for controlling weeds as a consequence of produced phytotoxic products, use is limited by batch-to-batch variability and logistical constraints. Our objective was to develop an efficacious bioherbicide by extracting and identifying the active ingredients in S. alba seed meal that demonstrate phytotoxicity to greenhouse-grown Powell amaranth (Amaranthus powellii) and green foxtail (Setaria viridis). Companion bioassays with separate potential active ingredient solutions containing ionic thiocyanate (SCN−), 4-(hydroxymethyl)phenol (4-OH), or 2-(4-hydroxyphenyl)acetonitrile (Nitrile) at concentrations approximating those in the extract were performed. When applied pre- (PRE) or postemergence (POST), SCN− and extracts were the most active solutions on both weed species. The highest rate tested of SCN− of 2.8 kg ha−1 controlled Powell amaranth 98% and green foxtail 84% compared to the highest rate of extract (2.8 kg SCN− ha−1) that controlled Powell amaranth 97% and green foxtail 82%. POST application of the extract was less effective as compared to SCN− solutions, with SCN− showing 97% control of Powell amaranth and 71% control of green foxtail as compared to the extract displaying only 46% control of Powell amaranth and 23% control of green foxtail. Little or no herbicidal activity was observed on both weed species following PRE or POST application of 4-OH or Nitrile. Development of a bioherbicide based on extracting and concentrating SCN− from S. alba seed meal is feasible, especially if scale up activities focus on eliminating the need for alcoholic extractants and yield higher active ingredient products.