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Clearfield hybrids recovering from early-season damage

Clearfield hybrid rice lines which showed damage from herbicide injury earlier this season appear to be recovering from the damage, according to most of those who observed or experienced the problem.

According to Van McNeely, technical services manager, RiceTec, the company that developed the hybrid technology for U.S. rice producers, around 95 percent of the rice that was reported to have had damage will reach its full yield potential — weather permitting a good harvest season.

“There are some fields out there we still have some concerns with. We’re working with those customers, and we will work with them all the way through harvest.”

McNeely, speaking at a company field day in Harrisburg, Ark., said that damaged Clearfield hybrid rice reported to the company comprised about 8 percent of acreage planted to hybrid rice this year. The damage primarily occurred on CL XL8 and to a lesser extent, CL XL730. Injury was reported in fields from south Louisiana to the Missouri Bootheel.

There were two separate reasons for the injuries, which were reported in late April and early May, according to RiceTec. The majority of the flashing, or herbicide injury, was due to “a problem with tolerance and/or environmental conditions which could be related back to a number of stresses, including the cool, cloudy, wet conditions, and Command was very active this year.”

McNeely said about 15 percent of the reported cases could be traced to Newpath injury. Other problems were related to herbicide drift and excessive water. And it was a strange season to say the least.

Noted Mike Martien, with RiceTec, “There were a lot of tractors in the field, then winter came back.”

There were also higher-than-normal occurrences of plant death in CL XL8. “We see this every year and will continue to see it to some extent every year,” according to McNeely. “With it being a hybrid, it’s an imperfect process and we are going to have some selfs (a self-pollinated plant which does not contain the resistant trait).

McNeely says that by law, a bag of hybrid seed “must be at least 75 percent hybrid seed. We try to get far above that with our quality assessments.”

The combination of higher-than-expected selfing and flashing in fields resulted in quite a number of thin-looking and yellowed stands. The problem wasn’t severe enough for rice consultants or RiceTec representatives to recommend widespread replanting, according to McNeely. The company reported that the percentage of replants were within historical expectations of around 2 percent.

Where self populations were concentrated, large gaps developed in the stand when the self died after being sprayed with Newpath. In most cases, surviving hybrids were able to compensate with additional tillering.

Arkansas rice producer Brian Stoner said his Clearfield rice hybrids tillered enough to fill in most of gaps, although he does expect a yield reduction in his CL XL730 and CL XL8. “I talked to Ford Baldwin (Practical Weed Consultants) who advised me to keep the stand. Research shows that most of the time you don’t gain yield by replanting. It looked pretty rough, but I took his advice.”

Today, Stoner’s crop “looks better than I ever thought it would.”

Stoner’s rice crop also suffered from glyphosate injury. “That was one thing that really complicated things in Brian’s area,” Baldwin said. “They had glyphosate drift over the top of Newpath injury on their hybrids.”

Baldwin had seen hybrid rice recover from similar injuries. “I saw a field several years ago that was about as bad as any I saw this year, and I would not have bought it for 100 bushels. It cut over 200 bushels. The hybrids do have a tremendous ability to overcome problems. But the combine will tell the tale.”

Baldwin said there may be added costs from herbicide injury in Clearfield hybrids. “It may be that the rice grows out and everything is fine, but in many cases, the farmer has had to flush once or twice when the rice should have been ready to flood. It’s taken one or two applications of fertilizer to try and get the crop to recover. That’s not cosmetic injury.

“I do feel like most of the rice will come back and yield fine, but the real story may be farmer acceptance of having to deal with a problem like this. If the new CL 170 AR and CL 151 AR turn out to be a step up from CL 131 and CL 161, the hybrids will have to step up, too. RiceTec feels like they have done that with their XP 729, and I hope they do.

“We need both these technologies to do well. The hybrid technology is still in its infancy and breakthroughs could come through a lot quicker. That’s the thing about hybrids. There are high expectations for it.”

Steve Linscombe, a rice breeder who works at the Rice Research Station in Crowley, La., where the first imidazolinone-tolerant plants were discovered and later marketed as Clearfield rice, said, “We did have some fields where yields were off somewhat and producers attributed some of the yield reduction to thinner stands that they thought were the result of the some of the injury. But the majority of the fields came back and are yielding pretty well.”

Linscombe saw considerably more injury that than he had seen before, some of which could be attributed to cooler weather. “We know from working with these Clearfield lines, that if we are going to get injury, it’s going to be more of a problem where we have less than optimum growing conditions for rice and it can’t recover as well. But we also saw this injury where we had ideal growing conditions.

“I didn’t know then what was wrong early on, and I don’t really know today,” Linscombe said. “We have known ever since we started working with RiceTec Clearfield hybrids that the level of resistance to Newpath is somewhat less than it is with CL 161 and CL 131. We also see a little more response to applications on the Clearfield hybrids than we do CL 161 and CL 131.”

Linscombe said on some fields the decision might have been made to forego a second application of Newpath, “but in my observations of rice fields, I have not seen a situation where we have rampant red rice in any of it. So we did a pretty good job of controlling red rice.”

While RiceTec doubled its customer base in 2006, the company said that grower inexperience was not a factor in any of the reported problems, noting that calls were evenly divided among all customers regardless of their experience with the technology.

RiceTec has formed a task force consisting of RiceTec staff, university research and rice consultants to investigate possible solutions and management recommendations for flashing seen in rice fields this season.

e-mail: [email protected]

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