In a good part of West Tennessee most soybean and cotton fields have at least some goosegrass and jungle rice (awnless barnyardgrass) present. In southwest Tennessee a good many cotton fields and particularly soybean fields have serious infestations of both of these grass species.
When one lays eyes on these fields it becomes clear we have a new weed management challenge to tackle. What is of most concern is the amount of jungle rice in some Xtend soybean fields that has survived at least 2 applications of a tankmix of Engenia, Roundup PM and 0.19 lb/A of a clethodim product.
As mentioned in an earlier blog we confirmed glyphosate-resistant jungle rice this past fall so the Roundup PM not working is not a surprise. However, in recent years when 0.09 lbs of clethodim was tankmixed with the glyphosate and a dicamba product good jungle rice control was achieved.
So when we see twice that rate having little impact we become concerned that the jungle rice has not only overcome glyphosate but may have developed resistance to clethodim as well.
The tolerance level of this jungle rice to clethodim is something we will be testing in the greenhouse this fall. We will also evaluate if the jungle rice is still sensitive to the Fop herbicide Assure.
As the combines roll this fall please pay particular attention to the grass control in your fields. Note fields or areas of fields where grass control has failed. These fields will clearly need to be managed differently next year with more thought on PRE herbicides to prevent jungle rice emergence as our POST options are looking thin.