Responses of three types of winter wheat ( Triticum aestivum L.) to spring-applied post-emergence herbicides

Abstract

Field studies were conducted over a three-year period (2002–2004) to evaluate the tolerance of recently developed varieties of winter wheat representing soft white winter wheat (SWWW), soft red winter wheat (SRWW), and hard red winter wheat (HRWW) to four spring-applied post-emergence (POST) herbicides. Bromoxynil plus MCPA, 2,4-D amine, dichlorprop plus 2,4-D, and dicamba plus MCPA plus mecoprop were applied at one and two times the manufacturers’ recommended dose. Bromoxynil plus MCPA and 2,4-D amine did not cause any visual injury. Dichlorprop plus 2,4-D did not cause injury in 2002 or 2003, but did injure all the three types of winter wheat 7 days after treatment (DAT) in 2004, but no injury was seen at 14, 28, and 42 DAT. Dicamba plus MCPA plus mecoprop caused injury in all the three types of winter wheat each year. Dicamba plus MCPA plus mecoprop at 600 g ai/ha reduced height 7% in SWWW and SRWW, while at 1200 g/ha reduced height 10% and 11% in SWWW and SRWW, respectively. Generally, winter wheat yield was not affected by 2,4-D amine, bromoxynil plus MCPA, or dichlorprop plus 2,4-D. In 2003, dicamba plus MCPA plus mecoprop at 600 g/ha decreased SWWW yield, however, when applied at 1200 g/ha, yield was decreased in all three years for both the SWWW and SRWW. The yield of HRWW was not affected by any of the herbicides evaluated. Overall, of the four herbicides evaluated, only the dicamba plus MCPA plus mecoprop POST caused unacceptable crop injury and yield loss in SWWW and SRWW.