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Escaped grasses in rice fields

I am getting the normal midseason rice herbicide questions. With the difficulty a lot of folks had getting herbicides applied timely, there will be some escaped grass.

Clincher is one of the first postflood herbicide treatments that come to mind. It has pretty good all-around activity on the different escaped grasses. Where barnyardgrass pressure is heavy, I have a lot more confidence in it when it is mixed with quinclorac. Clincher plus quinclorac also makes a nice combination for border-treating fields as well.

Where the grass problem is only barnyardgrass, I recommend mostly Regiment postflood. Be careful. You can not apply Regiment after panicle initiation or green ring, because severe injury can occur.

Ricestar HT is a good postflood treatment on broadleaf signalgrass and sprangletop. It can be a pretty good all around postflood grass treatment when mixed with quinclorac.

With all of these treatments, the earlier you can apply them postflood, the better they have a chance to work. Also keep in mind, with any of them, suppression may be the best you can hope for in some situations. That is why I am such an advocate of nothing but soil and rice in the field when you go to flood.

Broadleaf weed control seems to get more complicated every year. One of the best all around midseason broadleaf treatments continues to be propanil plus Grandstand. It will take out most of the black-seeded weeds, but may be weak on dayflower.

Be sure the crown of the rice plant is covered with water when using Grandstand, and do not use past the half-inch internode stage of the rice.

Where it can be used, 2,4-D provides excellent control of coffeebean, morningglories and dayflower. I hear some argue that this formulation or that formulation of 2,4-D is best on indigo. My experience has been they are all erratic on this weed. Remember again, the cutoff for 2,4-D on rice is half-inch internode elongation.

Where the only broadleaf weed is coffeebean or hemp sesbania, Ultra Blazer or propanil are the best treatments. Where the only weed is jointvetch or indigo, the best treatment is still Grandstand. I get more calls each year from growers wanting to get away from Grandstand at midseason. In that case, various mixtures of Londax, Ultra Blazer, Grasp and Permit or Halomax are the only options. Choices depend on the weed spectrum and adjacent crop situation. However, some of these treatments can be quite successful.

One weed I wish to address separately is pigweed on the levees. The pigweed population in Arkansas is exploding. I am constantly told, “I have pigweeds in rice fields where I have never seen them before.” Riding the roads, this is painfully obvious.

With pigweeds, the best approach is to treat them all as if they are glyphosate-resistant. This means if you allow ANY pigweed to go to seed in the rice field, it negates the benefit of the rice rotation for helping manage this weed.

The only effective herbicide I have found for pigweed control on rice levees is 2,4-D. At present, the regulations for spraying 2,4-D prevents levee spraying in many fields. In my opinion it is time to revisit this particular regulation. Weed resistance is changing the face of weed control faster than we can keep up. We have to be able to manage pigweeds on the rice levees and a hard look needs to be taken again at 2,4-D.

While history has proven that some regulations on 2,4-D have been necessary, I have never seen a major drift event caused by levee spraying. When drift does occur with levee spraying, the source is obvious. While I am not advocating the elimination of regulations on levee treatments with 2,4-D, I certainly believe glyphosate-resistant pigweeds demand we revisit the regulations.


TAGS: Rice
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