Rice weed control has changed markedly over the last five years, with lots of new products being used. All of the new products have brought much-needed improvements to rice weed control. While Command has arguably turned things upside down, we need to remember that old principles and standbys of rice weed control are not obsolete.
One concern I have is the popularity of post-flood Clincher. Don't take this wrong. Clincher is one of the best treatments available if you have grass after flood-up. My point is that a Clincher application means something went wrong — ideally we shouldn't have grass after flood-up.
I'm worried that we are shortchanging our pre-flood weed control programs and maybe even losing some yield to extra competition from uncontrolled grasses.
In our plots in 2004 we had several successes and failures. I'm not going to name names, but in one test we had several good programs where four different herbicides were sprayed in all sorts of different mixes at all sorts of different times. But in other tests we had good to very good results where one herbicide (propanil) was sprayed twice, or a tank mix (like propanil plus Prowl or Facet) was sprayed once.
If there is a revolutionary program, it's Command followed by an appropriate cleanup treatment. But guess what — the best cleanup treatment is good old propanil.
Broadleaf herbicides followed by Clincher are other good options to clean up escaped grasses from Command programs, but we need to be scouting a little better and if we need a pre-flood propanil treatment (or propanil plus Permit or Duet or anything else) we need to make that treatment.
Post-flood treatments should be your second choice, not your first.
Yes, you can mix and match all sorts of new chemistry, but you better have the right product at the right time. This may be one factor limiting the success of some of our newer chemistries. None of our recently-labeled rice herbicides is without weaknesses on several common weed species.
The Dow folks have a new herbicide coming (Grasp) that fits this “new-herbicide” mold. Much like Valent's herbicide Regiment, Grasp controls broadleaf weeds and barnyardgrass but does not control secondary grasses like sprangletop and signalgrass.
Many growers mention barnyardgrass and broadleaf problems (with no other grasses) at flood-up time. A herbicide like Grasp or Regiment has utility there. But neither herbicide provides standalone, season-long weed control. They need to be placed in carefully planned programs. My favorite program for these herbicides is pre-emergence Command or an early propanil application.
The Clearfield system is another new “extremely revolutionary” weed control system. On the other hand, the philosophy behind it all is about as old-fashioned as it gets. Start early, spray twice and throw in a mix partner as needed. The Clearfield-Newpath program uses the very same application scheme the age-old 3+3 propanil approach (maybe things happen a few days earlier, but not much).
Just as with the old approach, you do need to scout carefully and be prepared for the occasional failure (we have Beyond for as-needed cleanup now). The difference between Clearfield and propanil is that propanil won't control red rice and Newpath won't control coffee-bean and indigo.
What's the best thing to add to our newest program? Good old propanil!
None of our new chemistry — including Command — comes close to being standalone weed control in rice. Every new product has a list of weeds it does not control. However, each brings something we didn't previously have. If they didn't, we would still be using 3+3 propanil for everything.
My point is not to send us back to those days, but to remind us that the best weed control comes when the new herbicides are integrated into traditional programs. We need to make sure we don't throw out the baby with the bathwater when we start using new herbicides.
Andy Kendig is an Extension weed specialist at the University of Missouri Delta Center.