Junglerice (Echinochloa colona) Control with Sequential Applications of Glyphosate and Clethodim to Dicamba
Abstract Junglerice is becoming more prevalent in Tennessee, Arkansas and Mississippi row crop fields. The evolution of glyphosate-resistant junglerice populations is one reason for the increase. Another possible explanation is that glyphosate and clethodim grass activity is being antagonized by dicamba. This question has led to research to examine if sequential applications alleviate antagonism observed with dicamba plus glyphosate and/or clethodim mixtures and determine if 24 h, 72 h or 168 h sequential treatments of those herbicides can improve junglerice control. Glyphosate + clethodim applications provided >90% junglerice control. The observed levels of antagonism varied by whether the location of the test was in the greenhouse or the field and the timing of applications. In the greenhouse, clethodim + dicamba provided excellent control while in the field the same treatment showed over a 30% reduction in junglerice control compared with clethodim alone. However, control was restored by using a mixture of glyphosate + clethodim without dicamba. The environment at the time of application and relative glyphosate-resistance (GR) level of the junglerice influenced the overall control of these sequential applications. Clethodim applied first followed by dicamba at 72 or 168 h, better control was observed compared with applying dicamba followed by clethodim. Overall, mixing glyphosate + clethodim provided the most complete junglerice control regardless of timing. These data confirm that leaving dicamba out of the spray tank will mitigate herbicide antagonism on junglerice control. These data would also indicate that avoiding dicamba and glyphosate mixtures will also improve the consistency of control with glyphosate-susceptible junglerice.