Rice weed control and resistance

In my past several articles on rice weed control I have emphasized the use of residual herbicides before grass emergence.

My philosophy of barnyardgrass control is every plant you can keep from emerging is simply one that can not get too big to kill. Pre-emergence weed control is only part of the equation. Not everyone will get the pre-emergence herbicides applied and properly activated, and they do not always provide 100 percent control.

The next step after pre-emergence weed control is to be scouting carefully for the first sign of grass emergence. Do not take the pre-emergence herbicides for granted and assume they will provide 100 percent control.

Some growers get used to the Command or other pre-emergence treatment working so well that they may not look behind it as carefully and quickly as needed.

The opportunity to control barnyardgrass starts going away quickly when it gets past the two-leaf stage.

In most cases for the first postemergence application, a contact plus residual herbicide will be the best choice for both control and resistance management. There are too many combinations of contact and residual herbicides to try and cover them all. In most cases the timing will be more important than the choice.

In conventional rice, combinations of Ricestar HT, Regiment, propanil, or Clincher with Command or Facet all have a place.

Ricestar HT plus Command or Facet has been an extremely popular treatment the past few years.

Where the grass is only barnyardgrass, 0.2 to 0.25 ounce of Regiment is an excellent choice with Command or Facet. With Regiment always use the Dynapak or equivalent surfactant and the rice should be a uniform two-leaf or larger.

For barnyardgrass, the Ricestar HT, Clincher, and Regiment programs are often better choices than a propanil product simply due to the widespread resistance to propanil.

In Clearfield rice, again look hard at tank mixes in the first postemergence application. If extra residual is needed, Newpath plus Command, Clearpath or Newpath plus Facet can make nice treatments.

Again, because of the selection pressure we are putting on barnyardgrass with the ALS inhibitors, I do not suggest depending on Newpath alone, even at the 6-ounce rate, if emerged barnyardgrass is a problem.

There are situations in the first Newpath application where a contact herbicide may be needed. Often, just a couple of quarts of propanil are all that is needed.

RiceBeau is propanil and Bolero and it can have a place.

While some would say mixing two ALS inhibitors is unwise, Newpath plus Regiment can be an impressive treatment in certain situations.

It is just getting more difficult to write about rice weed control because of the resistance issues. That is another reason I like to kill grass before it comes up.

I can tell you Newpath plus Facet or Clearpath is a great treatment. However if you have Facet-resistant barnyardgrass, it may fail.

Propanil plus Newpath can often be excellent, but if you have propanil-resistant barnyardgrass, it may fail.

In conventional rice, a gallon of propanil plus a half pound of Facet has been a good treatment. However, if you have both propanil- and Facet-resistant grass, it is going to fail.

My best advice it to manage around the resistance problems you know you have by choosing alternatives.

Whether it is the first postemergence application in conventional rice or Clearfield rice and there is enough emerged barnyardgrass to be a problem, do not cut costs. If you do not kill it right then, there is a good chance you may fight it all season.

Pick a contact plus residual treatment with multiple modes of action and hit it early and hit it hard.

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TAGS: Soybeans
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