Phytotoxic effects of volatile oil from Artemisia scoparia against weeds and its possible use as a bioherbicide

A study was conducted to assess the bioherbicidal activity of volatile oil hydrodistilled from Artemisia scoparia Waldst et Kit. (red stem wormwood; Asteraceae) against five weed species, viz. Achyranthes aspera, Cassia occidentalis, Parthenium hysterophorus, Echinochloa crus-galli, and Ageratum conyzoides. Emergence and seedling growth (in terms of root and shoot length) were significantly reduced in a dose–response bioassay conducted in sand impregnated with Artemisia oil (at ≥10, 25, and 50 μg Artemisia oil/g sand). In general, the root length was inhibited more as compared to the shoot length and the inhibitory effect was greatest in P. hysterophorus followed by A. conyzoides and least in C. occidentalis. Post-emergence application of Artemisia oil (2%, 4%, and 6%, v/v) on 6-week-old weed plants caused visible injury (1- and 7-days after spray) ranging from chlorosis to necrosis to complete wilting of plants. Among the sprayed test weeds, the effect was greatest on E. crus-galli and P. hysterophorus. Artemisia oil treatment resulted in a loss of chlorophyll content and cellular respiration in test weeds thereby implying interference/impairment with photosynthetic and respiratory metabolism. Artemisia oil caused a severe electrolyte leakage from E. crus-galli (a monocot) and C. occidentalis (a dicot) indicating membrane disruption and loss of integrity. The study concludes that Artemisia oil has bioherbicidal properties as it causes severe phytotoxicity and interferes with the growth and physiological processes of some weed species.