Crop injury caused by drift of auxin-like herbicides has been a concern since their development. Research was conducted to describe a method of quantifying injury from auxin-like herbicides as a first step in determining crop damage. Reduced rates of 2,4-D, dicamba, and triclopyr were applied to cotton and soybean plants in the three- to six-leaf stage in field and greenhouse studies. Injury to leaves and stems were evaluated separately, and the values were combined so that one injury estimate was obtained for each individual plant rated. Injury symptoms were typical for auxin-type herbicides and ranged from slight bending of stems or petioles and wrinkled leaves to necrosis. Specific descriptions of leaf and stem injury levels were used to describe plant injury consistently. These descriptions were very detailed for the lower injury levels, but the characterizations became more general as the injury increased because of the prominence of factors such as necrosis. The injury evaluation method provided repeatable results for each herbicide and herbicide rate used. This injury evaluation method has many possible uses in auxin-like herbicide research and lays the foundation for forecasting the impact of early-season injury to cotton and soybean yield.

Field studies were conducted near Knoxville, TN, during late March and early April 2002 and 2003, respectively, for star-of-Bethlehem control in dormant bermudagrass turf that was established over 25 yr ago. Halosulfuron, imazaquin, metsulfuron, 2,4-D plus dicamba plus mecoprop, and triclopyr plus clopyralid controlled star-of-Bethlehem 35% at most 35 d after treatment (DAT). Bromoxynil alone or mixed with halosulfuron, imazaquin, or metsulfuron controlled star-of-Bethlehem at least 80% at 35 DAT. Imazaquin and imazaquin plus bromoxynil injured bermudagrass 51% 35 DAT. This injury was characterized by decreased bermudagrass postdormancy transition and was transient.