Effect of Metribuzin and Two Analogs on Five Species of Algae

Growth response of five species of soil algae to 4-amino-6- tert -butyl-3-(methylthio)- as -triazin-5 (4H)one (metribuzin) and its 6-isopropyl and 6-cyclohexyl analogs were studied in vitro. Species of Chlorella, Chlorococcum, Chlamydomonas , and Anabaena were exposed to 0.05, 0.1, 0.5, and 1.0 ppm (w/v) of the herbicides in liquid nutrient, while a species of Schizothrix was studied at the same levels in soil culture. With one exception, the growth and numbers of all of the algae were significantly reduced by increasing herbicide concentrations. Anabaena was not affected by 0.05 ppm of the cyclohexyl analog. No growth was permitted by any of the herbicides at 1.0 ppm. Chlorella and Chlamydomonas could not grow in the presence of 0.5 ppm of metribuzin or the cyclohexyl analog. Differences in response to the triazinones were noted between species. Chlamydomonas was the most sensitive and Anabaena and Chlorella the most resistant.