Rice weed control in the Mid-South is beginning to show signs of distress due to weed resistance, a dearth of new chemicals on the market and the lack of movement toward trait-based technology, according to weed consultant Ford Baldwin.
Baldwin, a Delta Farm Press contributor and former Extension weed scientist at the University of Arkansas, told attendees of the USA Rice Outlook Conference that several disturbing field observations have led him to this conclusion.
Grass control has gotten much more difficult. “We are seeing it more and more in Arkansas. If barnyardgrass gets through the pre-emergence herbicide, we have a very difficult time killing it. We can apply Clincher, Ricestar HT and Facet and get 60 percent to 70 percent control. We can come back with something else to kill 60 percent to 70 percent of that, but before you know it, we’ve spent $100 an acre pretty quickly and still may wind up cutting a grassy crop.
“It takes moisture or rainfall to activate pre-emergence herbicides. The years we get nice rainfall, things work well. The year it’s dry, it’s not working, and farmers don’t like being told they have to flush. But a lot of times, a $10 to $20 flushing cost may save you $100 an acre in herbicide costs.”
Baldwin says there are two confirmed samples of barnyardgrass resistant to Command in Arkansas. I hope it’s not something that is going to blow up in our faces. We know it can happen and if it spreads, we’ve got big time trouble.”
Grassy soybean fields — “After Roundup Ready came out, you didn’t see a weed in soybean fields. I don’t know if it’s the price increase of glyphosate or what, but I’m seeing more and more farmers backing off one application of glyphosate, delaying the timing or even knocking barnyardgrass down to the point where it’s not affecting yield. What happens though, is it’s not dead, and when the leaves fall off the soybeans, it flourishes again and makes seed.
“It worries me that we’re dealing with resistance in barnyardgrass, and yet we’re building our seed bank tremendously by simply not controlling this weed in our soybeans when we have super technology to do so.”
Poor sprangletop control — Baldwin said he received many calls this year about lack of control with Ricestar HT and Clincher in perfect conditions. “Weed control fails for a lot of reasons besides resistance, but after they ran the two samples in the greenhouse, you start to wonder.”
Baldwin was referring to testing by University of Arkansas weed scientist Jason Norsworthy which confirmed sprangletop samples resistant to a 10X rate of Clincher. “If it’s resistant to Clincher, more than likely it’s also resistant to Ricestar HT. Those have been our go-to herbicides for sprangletop control, especially if it gets by one of our pre-emergence treatments.”
There were also some Command failures “that simply seemed like they should have worked,” said Baldwin.
Continued dramatic increase in Clearfield acres without a backup plan — “I’m a big fan of Clearfield rice. But I’m hearing Arkansas could plant up to 75 percent of our acres in Clearfield varieties. You better think long and hard about it. Some of the weediest messes I saw were late-planted rice in Clearfield. The weeds blew right through two applications of Newpath.”
Increasing amount of volunteering behind Clearfield hybrids — This year, when the hurricanes hit, we had shattering levels way above what would be typical. It’s been proven that those shattered hybrids have the capability to carry over and volunteer back the next year.
“I don’t know what the volunteer potential of some of these hybrids are, but there is a lot of diversity out there. I don’t know that they aren’t going to be a problem, but I don’t know that they are either.”
The dearth of new herbicides — “From a farmer’s standpoint, resistance has not been that big a deal because there were always new products coming. I spent most of my career getting to talk about new herbicides. We don’t have them coming out now. The ballgame is changing.”
Baldwin points out that it’s often easy for a grower to get behind the curve on a case of herbicide resistance. “The first year, you see a few escapes, you don’t think a lot of it. You see a few more the next year, you think it’s just a bad year. The next year, you really step it up and make sure you do everything right. You up the rate and drop the hammer on it, and you have even more escapes. You pull a sample and you find out it’s resistant. Then you’re three years behind the program.
“I’m afraid that we’re seeing some of these situations out in the field. I wouldn’t be surprised if we see confirmed ALS resistant barnyardgrass this year, ACCase as well.
“What can we do now? Rotate crops. Don’t plant rice behind rice. Don’t plant Clearfield rice behind Clearfield rice. We can rotate herbicides, but on a lot of fields, we’re using them all now. That’s scary.”
Baldwin says a better stewardship strategy for Clearfield will help, “but I don’t know what that’s going to be if we’re going to plant 75 percent of our acres in Clearfield rice.”
Baldwin says a move toward trait-based weed control technology would help. “That is where it’s happening in other crops. We all know about the LibertyLink situation in rice, but I don’t see anything else close to providing us help.
“I think all of the decisions made so far on LibertyLink rice have been right. Lawsuits complicate things in that they stop dialogue. I understand that it’s not going to work without marketing acceptance, but I also realize that if weeds continue to box us in, we’re not going to have to worry about marketing segments if we can’t grow the crop. We’re not there yet, and we won’t be there next year. But in three years, in my opinion, farmers will be begging for that technology. I hope we can get some dialogue started on the issue. I don’t see a lot of other options either.”
Rather than spend $100 an acre on weed control, farmers may simply go to crops with better technology,” Baldwin says. “I haven’t heard anyone say they’re not planting a field to rice because they can’t control weeds on it, but I think that time is coming.
“We have great university weed scientists and great people out in the field, but we’re getting boxed in. If the rice industry is not going to go with traits, we better be thinking about what Plan B is going to be.”
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