Scout rice for barnyardgrass
May 11, 2009 11:25 AM,
By Ford L. Baldwin
Practical Weed Consultants, LLC.
A lot of Arkansas rice has been planted between writing last week’s article and this one. That is a good thing, but windy conditions have made spraying difficult.
It is a little early to tell if this will be a “throw the book out” year like 2008 or not. Normally when things do not go as planned on the front end, weed problems increase.
You can count on weeds that emerge in May growing much faster than weeds that emerge in late March and early April. That simply means things can get out of hand much quicker in later-planted rice.
If you have used only Command and think it is doing a good job to this point, scout carefully. If you have any escaped grass at all, I would encourage you to kill it.
I get calls from growers and consultants who tell me, “I didn’t have to use anything but Command,” or “I had a few grass escapes following my Command, but not enough to justify spending any money on.”
I have seen fields like this in previous years. I am all about getting by cheaply. However, Command is the glue that holds most of our weed control programs together, and we do not need any increase in the spread of Command resistance.
Escaped barnyardgrass plants are not necessarily resistant, but if you kill them, you do not take any chances.
I wish we had a comparable pre-emergence herbicide to rotate with Command for resistance management. However, we really do not — even in Clearfield rice. That means Command will continue to be used on the majority of the fields every time they are in rice.
Therefore, the only resistance management program for Command is to make sure you control any escapes that may occur.
Based on my calls and growers’ experiences the past few years, if you do not kill barnyardgrass before it reaches the four-leaf stage, chances are good that you will spend a ton of money fighting it the rest of the season.
I also recommend that you keep a close eye on sprangletop. Loosehead sprangletop has generally been easy to control with Ricestar HT. It is easily identified by its pale green color, long slender leaves and white leaf midrib.
Tighthead sprangletop, on the other hand, is much more difficult to control. It is also more difficult for most to identify. I can best describe it as looking like barnyardgrass but having a long leaf ligule.
Jason Norsworthy at the University of Arkansas has found two populations of tighthead sprangletop from north Louisiana that have tested resistant to every rate of Clincher and Ricestar HT he has sprayed on them.
Several things could make this a “sprangletop year.” Roughly one-half of the rice acres are planted to Clearfield rice. Both Newpath and Beyond are relatively weak sprangletop herbicides. Hopefully most of the Clearfield rice will be treated with Command and this should take care of the problem. However do not take this for granted — scout.
Another factor that can make sprangletop worse this year than normal is the wet spring. Sprangletop germinates best in warm, saturated soils. We have had no shortage of saturated soils in most areas. Much of the rice is planted no-till or into stale seedbeds, and emerged sprangletop can be easy to miss with a glyphosate plus Command tank mixture.
I am not trying to create a problem here but rather trying to create awareness. We had some sprangletop control problems across the state last year with the wet weather. Because of this I would suggest scouting carefully and spraying early.
While large loosehead sprangletop can sometimes be killed with Ricestar HT or Clincher, do not chance it — spray early.
Large tighthead sprangletop can seldom be killed with either herbicide. If this weed is present, spray it in the two- to three-leaf stage with maximum rates of Ricestar HT or Clincher and do not tank mix them with anything to risk loss of activity due to antagonism.
e-mail: ford@weedconsultants.com
