Grass control in Clearfield rice
Dec 11, 2008 9:33 AM,
By Ford L. Baldwin
Practical Weed Consultants, LLC.
Last week I wrote about the need to control barnyardgrass before it emerges. Where this does not happen, it must be controlled by the two- to three-leaf stage. Once barnyardgrass gets past this stage it becomes very hit or miss whether you can get it under control.
We are fortunate to have some herbicides such as Regiment, Grasp and Clincher that sometimes will kill some big grass. However, big grass robs yield and often is impossible to control.
Last week I outlined some programs to make optimum use of residual herbicides in conventional rice. This week I’ll focus on grass control in Clearfield rice.
One philosophy of grass control in Clearfield rice is just to use Newpath and Beyond. Sometimes this can be successful. However, some of the worst messes I saw last year were in Clearfield rice. Resistance to the ALS inhibiting herbicides such as Newpath and Beyond (and also Regiment and Grasp) is usually the result of a point mutation that either exists in the weed population or results from the use of the herbicide.
Further exposure to these herbicides simply kills the susceptible weeds and selects for the resistant ones. Once resistance to the ALS herbicides is confirmed, it spreads very quickly and the herbicides become ineffective.
At this point, I do not know if any of the difficulty controlling barnyardgrass with Newpath last year was due to resistance. If it was not, it soon will be if we over-depend on ALS inhibiting herbicides in the Clearfield system.
I recommend that Clearfield programs begin with Command. In conservation tillage programs the Command can be applied before planting with the burn-down herbicide or as a pre-emergence herbicide as it would be used in conventional tillage systems.
In the first Newpath application you have the option of adding more Command to extend the length of residual and help on sprangletop control.
There is also the option of using Clearpath or a quinclorac tank mix for the first application.
If you add some more Command in the first Newpath application, consider Clearpath or some quinclorac in the second.
There is also the option of mixing several of the postemergence herbicides with one of the Newpath treatments.
You may say, “You are recommending as much conventional herbicide in the Clearfield program as you would with a conventional variety.” That was precisely the comment I received from several consultants last year. They commented that they had to use Newpath and Beyond for red rice control but also just as much conventional herbicide as they would have needed in a conventional variety to control the other weeds.
I am a huge fan of the Clearfield technology. However, increasing the acreage past what is needed to manage red rice may well be counter-productive.
In addition, if we do not increase the diversity in herbicide use patterns in the Clearfield system, resistance will develop quickly. Increasing the diversity in use patterns does mean you will be spending a lot on conventional herbicides in the system. This may provide some food for thought on how much the acreage really needs to be increased above those needed to control red rice.
I also have a big concern over the amount of shattering in the Clearfield hybrids. A significant amount of these shattered seed will survive the winter and volunteer the next year. I am concerned that we may create a Clearfield weedy off type other than resistant red rice.
As I have stated before, there has been no demonstrated effort on the part of the industry to steward the Clearfield system. If stewardship is successful, it will be at the grower level.
If we continue to expand the Clearfield acres onto fields where conventional programs would work equally well, continue to plant Clearfield rice in consecutive years, fail to get more herbicide diversity into Clearfield programs, and plant rice in fields where a lot of hybrid shattering occurred this year, we are digging a huge hole in front of this excellent technology, taking a bulldozer and shoving the technology right off in it, and covering it up.
e-mail: ford@weedconsultants.com
