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Rice and soybean farmers tuned to barnyardgrass threat

I have had a lot of interesting comments about my recent articles about barnyardgrass. One former university colleague now at the University of Minnesota e-mailed that he is seeing some of the same barnyardgrass control failures with glyphosate that we are seeing down here.

I firmly believe barnyardgrass is becoming more difficult to control with a lot of herbicides. However, a lot of our problems are self-inflicted.

It has been interesting how many comments and questions that I have had on LibertyLink soybeans since some of my recent articles in Delta Farm Press. One was, “It looks like the timing has to be much earlier than with glyphosate on Roundup Ready soybeans — isn't that going to be a big disadvantage?”

After several of those comments, I decided to dust off a University of Arkansas 2008 MP 44 (Recommended Chemicals for Weed and Brush Control in Arkansas), thinking maybe the Roundup Ready weed control recommendations had changed since I helped write them in the mid 1990s. Not so. The recommendation still calls for the first glyphosate application at 10 to 14 days after soybean and weed emergence followed by a second application seven to 14 days later.

I do not know what application timing for Ignite in LibertyLink soybeans will be recommended.

If I were writing it today, it would be worded exactly like the UA glyphosate recommendation in Roundup Ready soybeans.

Under good growing conditions, you can kill some big weeds with glyphosate. In fact, you can consistently kill some weed species that are large in size. Herein lies the trap. The fact you can sometimes kill big weeds leaves the impression you always can.

A typical Arkansas soybean field will have weed species — some grasses and non-resistant pigweeds — that a single glyphosate application may kill at almost any timing.

However, those same fields might also have species such as barnyardgrass, morningglories and hemp sesbania which might be controlled only with two timely applications and under good growing conditions.

It is obvious that some growers have gotten away from the basics of two timely glyphosate applications. I frequently hear, “I just wait and hit them one time — I may have a few weeds but they do not reduce my yields.”

That might be true, but watch what happens to the “non-competitive” barnyardgrass population buried down in the canopy when the soybean leaves drop. The grass flourishes and produces a tremendous seed crop.

Bob Scott with the University of Arkansas told me he had been inundated with telephone calls from county agents, consultants and growers telling him they would be sending in barnyardgrass samples for resistance testing. If you suspect resistance problems in a field, I encourage you to do the same.

Resistance is never a problem until it is on your farm. The glyphosate pigweed resistance issue is huge. Hopefully the LibertyLink soybean technology will ramp up quickly enough to allow you to implement a much better herbicide rotation program for this species.

With Arkansas being the number one rice producing state, I believe barnyardgrass resistance is potentially a greater problem.

The rice crop across the state this year should speak to the fact that in many cases barnyardgrass escaped everything the grower threw at it.

One friend has a field of barnyardgrass that escaped Command, two applications of Newpath, Beyond, Ricestar HT, Facet and Clincher. This man is an excellent farmer. If that does not get your attention, I don't know how to.

I don't know if his grass will test resistant to any of the herbicides used, but it doesn't matter if it is resistant or not if you can't kill it.

We cannot continue to mess around with this grass in soybeans.

Through the years we have had a “Get the Red Out” program for red rice and even further back a “War on Cocklebur” program in soybeans.

We need to implement a “Fight Barnyardgrass Like You Are Mad at It” program on the whole farm.

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