Was rain enough to activate herbicide?

Growers should be looking closely at their rice fields. Rain in a lot of areas has been marginal for activating Command. One thing I like about the herbicide is it activates with very little moisture, but it does take some.

I had a lot of calls along the lines that “I got 0.2 inch or 0.25 inch of rain. Will that activate my Command?” On stale seedbed or a seedbed packed with a roller, it usually will. On cloddy or fluffy ground, it likely will not. The first grass emerging will tell you whether or not it has been activated.

I am not predicting gloom and doom for Command this year. I think it will still work well. However, our rainfall pattern has been sporadic enough that there may be more early grass in some fields than we had last year. Look close and if it gets to three-leaf and is green, take it out.

I am getting quite a few questions on Ricestar. I've read the company literature and Website. Some of our recommendations are slightly different than theirs.

On rates, our data would indicate the 13-ounce rate is fine for small (one-leaf to early three-leaf) grasses in most cases. This is especially true if you are going to use two applications of Ricestar — as in a propanil followed by propanil scenario. If, however, the grass situation includes a lot of barnyardgrass and it gets to the late three-leaf to early four-leaf stage, you had better be at 17 ounces if you are making a single treatment. I really believe that for all practical purposes, the way most of it will be applied, the rate should just be 17 ounces per acre, period.

The label discourages tank-mixing with Facet. In our research, Facet has been an excellent tank-mix partner where barnyardgrass is four-leaf or larger and/or if some residual control is needed. It is a big help on barnyardgrass and can be on broadleaf signalgrass.

We have not had enough sprangletop in our tank-mix tests to be 100 percent certain there could not be some antagonism problems with the Facet mixture on sprangletop. However at this point, we have not seen any.

A lot of the questions are about the largest grass Ricestar will kill. Our data indicates, even with four-leaf barnyardgrass, you had better be counting all of the leaves. It is not a big barnyardgrass herbicide. On broadleaf signalgrass and sprangletop, we have been successful all the way to our preflood timing. I have not seen it on headed-out sprangletop, about which I get most of the sprangletop calls.

Where I will really cross with the label is on the tank-mixes with broadleaf herbicides. Perhaps on one-leaf to three-leaf grasses, the tank-mix with broadleaf herbicides will work. However in the tank-mix work we have done on four-leaf to five-leaf grasses, we have seen a lot of antagonism problems with some of the mixtures.

A lot of people are going to want to mix Permit for annual sedge and nutsedge control. In our work, it has caused severe loss of grass activity. Antagonism work is hard to do because the level of antagonism can vary greatly from test to test.

To date, Aim and Basagran have not caused a lot of antagonism. My recommendation, however, is to not tank-mix any broadleaf herbicide. This is an ultra-conservative approach, but our data would indicate that if you are pushing the limit on grass size to start with and you want to tank-mix with some of the more popular herbicides such as Grandstand, Londax, Duet, Permit, propanil or Stam, there will be antagonism problems. That will result in loss of grass activity.

Ford Baldwin is an Arkansas Extension weed scientist.
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