Nader Soltani*, Christy Shropshire and Peter H. Sikkema
Pyroxasulfone is a new herbicide being developed for weed control in corn, soybean and other crops prior to crop emergence. There is little information on the tolerance of spring planted cereals to pyroxasulfone under Ontario environmental conditions. Four field studies were conducted in Ontario over a three year period (2009 to 2011) to evaluate the tolerance of spring planted barley, durum wheat, oats, and wheat to pyroxasulfone applied preemergence (PRE) at 62.5, 125, 250, and 500 g ai ha-1. Regression equations were used to calculate the predicted pyroxasulfone doses (g ai ha-1) that resulted in 5, 10 or 20% injury, or a 5, 10 or 20% reduction in percent height and yield. The dose of pyroxasulfone that caused 5% injury in spring planted barley, durum wheat, oats, and wheat was as low as 23, 14, 7, and 164 g ai ha-1 at 1 WAE; 40, 13, 7, and 127 g ai ha-1 at 2 WAE; 33, 9, 5, and 142 g ai ha-1 at 4 WAE; and 38, 14, 8, and 119 g ai ha-1 at 8 WAE, respectively. The dose of pyroxasulfone that caused 5, 10, and 20% reduction in height was 80, 160, and 321 g ai ha-1 in barley; 30, 58, and 128 g ai ha-1 in durum wheat; 16, 30, and 59 g ai ha-1 in oats; and 149, 299, and >500 g ai ha-1 in wheat, respectively. The dose of pyroxasulfone that caused 5, 10, and 20% reduction in yield was as low as 31, 63, and 126 g ai ha-1 in barley; 25, 49, and 98 g ai ha-1 in durum wheat; 8, 16, and 34 g ai ha-1 in oats; and 122, 244, and 489 g ai ha-1 in wheat, respectively. Based on this study, among spring planted cereals evaluated, wheat is the most tolerant, followed by barley and then durum wheat while oats are the most sensitive.
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