There is another resistant weed sneaking up on us in rice, and it is one I would have least expected — rice flatsedge. In years past this was a weed that propanil kept knocked back and it was not very competitive anyway. We used to chase it in our research program after Command came along because it tends to release rice flatsedge. We would do the plot work and get some treatment differences, but the rice would wind up just choking it out on its own.
When I began to get calls on rice flatsedge (annual sedge) overgrowing hybrid rice after multiple applications of Newpath and Permit, I couldn’t believe it. I went to the fields and still could not believe it. Sedges can be difficult to identify and I thought, “man this can not be rice flatsedge — this stuff is on steroids!”
We sent some samples to the University of Arkansas herbicide resistance testing program headed up by Jason Norsworthy. It has been positively identified as rice flatsedge and it is completely resistant to the ALS inhibiting herbicides such as Newpath and Permit.
This is another reason you can not take weeds for granted. You must manage every field in every crop like you have resistant weeds. “I do not have any resistant weeds yet so I am just going to keep on with what is working” will pretty much guarantee you a resistance problem.