Growth of Kochia scoparia, Salsola iberica, and Triticum aestivum varies with temperature

Information on the influence of temperature on growth of spring Triticum ae stivum L. (wheat) relative to Kochia scoparia (L.) Schrad. (kochia) and Sal sola iberica Sennen and Pau (Russian thistle) could lead to more efficient weed management practices. An experiment was conducted to determine the gro wth of spring T. aestivum, K. scoparia, and S. iberica at 15, 23, and 30 C in growth chambers. Fresh weight at. 15 C was greater for spring T. aestivu m than for K. scoparia and S. iberica. Conversely, fresh weights at 23 or 3 0 C were greater for k: scoparia and S. iberica than for spring T. aestivum . Growth response to temperature is consistent with the physiological chara cteristics for photosynthesis of spring T. aestivum, a C-3 plant, and K. sc oparia and S. iberica, which are C-4 plants. The results indicate that cool temperatures that usually occur for early-seeded spring T. aestivum would give spring T. aestivum the competitive advantage over K. scoparia or S. ib erica. Additionally, growing degree day (GDD) equations for height developm ent of K. scoparia and S. iberica were determined and could be used to dete rmine the optimum time for postemergence herbicide application.