Tuesday, April 23, 2024

Panel Discussion Takeaways

Experts addressed the theme ‘Provisia — save the technology’ during a recent conservation forum.


Author’s note: At the end of January, Horizon Ag hosted a Provisia Rice Panel during the National Conservation Systems meeting in Jonesboro, Arkansas. Participants included Drs. Tim Walker, Jason K. Norsworthy and L. Connor Webster. Following are some key takeaways from that forum.

Dr. Tim Walker, Horizon Ag general manager, kicked off the discussion by getting right to the point.

“Once we lose the Provisia Rice System, we’re not aware of anything that is up and coming in the next few years to replace Provisia from a weedy rice management standpoint,” he said. “It is of dire importance that we take care of the tool we have with Provisia rice.”

From left, the Provisia rice panel included Drs. Jason Norsworthy, University of Arkansas weed scientist; Tim Walker, Horizon Ag general manager and Connor Webster, LSU AgCenter rice weed scientist.

Dr. Connor Webster, rice weed scientist at the LSU AgCenter, started working with the Provisia Rice System in 2017.

“In Louisiana, we have about 15 populations of outcross with the Provisia system that we confirmed two years ago,” Webster said. “This past year, we saw about six different populations of outcross, so we are trying to tackle this head on with best management practices.”

Dr. Jason Norsworthy, weed scientist with the University of Arkansas, began working with the Provisia Rice System two to three years prior to its launch. “We have three new populations in Arkansas I confirmed resistant to quizalofop this past year,” Norsworthy said. “I had 21 or 22 samples that came in for screening in the herbicide resistance screening program for weedy rice and they all tested positive for resistance to imazethapyr (Newpath).”

Residual, No Residual

An important point to consider is that the Clearfield Production System for Rice included Newpath herbicide, and the FullPage System included Preface herbicide. Both of these residual herbicides would carry you to flood, which meant there was little risk of outcrossing. In the Provisia Rice System, Provisia herbicide has no residual activity associated with it.

Provisia variety PVL03 is the most planted rice seed line in Louisiana.

“This changes how we think about the timing of our herbicides and how we position the Provisia rice weed control program,” Norsworthy said. “We’ve got to do something different. We’ve got to get soybean into the rotation.”

Webster adds that when they documented their first Provisia-resistant weedy rice, he asked the grower about his field history to learn what might have contributed to the resistance.

Rates And Timing

Norsworthy said that Provisia rates, timing and the inclusion of Rogue herbicide is a good strategy to help control weedy rice.

“I think one of the biggest mistakes we made early on was applying 15 ½ ounces of Provisia following by another 15 ½ ounces,” he said. “Because Provisia has no residual, weedy rice starts emerging before you get to flood, and there are no bullets left in the gun.

“Our current recommendation is to put Command — or clomazone — herbicide down at planting so it can help remove barnyardgrass, sprangletop and all the other grasses out there that reduce the coverage of Provisia herbicide. So, I like to start out with Command at a low pre and then at 2-leaf, overlay it with 11 ounces of Provisia. Then I come back at pre-flood with another 10 ounces of Provisia. As soon as the flood is established and there is some open canopy, I’m going to apply another 10 ounces of Provisia.”

Where there is a zero-grade field with side-inlet irrigation, Norsworthy includes Rogue herbicide in the mix. If weedy rice has emerged and is beneath the flood, Rogue will kill it. If it’s above the flood, Provisia will take it out.

“This is a planned weed control program that starts at Day 1,” Norsworthy said. “You have to go into the season with a planned approach. Also, if you have cold, wet, cloudy conditions, you are likely to see injury. When this happens, the worst thing you can do for the outcrossing weedy rice scenario is stop spraying. If you quit spraying, the weedy rice is going to outcross and the technology is as good as dead in that field.”

Rice/Soybean Rotation

During the discussions, the panel continued to promote implementing a rice/soybean rotation. Some takeaways include:

If you are inundated with Clearfield-, FullPage-resistant weedy rice, you are better off going into soybeans.

If you have low populations of the resistant weedy rice, you are better off going into the Provisia rice system.

Although glyphosate herbicide is an excellent grass material, like Provisia it has no residual. Be sure to include herbicides with residual activity before barnyardgrass produces a viable seed. Growing a soybean crop that has grass seed production in the crop means you haven’t moved forward in terms of managing the soil seed bank.

If you are going to protect Provisia, there is no reason to plant anything other than soybean behind it.

A pertinent question from the audience addressed herbicide strategy in drought-stressed conditions. “What weed management strategy should be followed when rice is planted later in the season and it’s time for pre-flood herbicide applications, but the planted rice and the weedy rice are stalled out and there is not much herbicide metabolizing going on?”

Norsworthy said his recommendation is don’t change the course. “Even if the plant is stressed, and Provisia is not going to be as effective in that scenario as it would if you had good growing conditions and high moisture, you are still going to have some activity. What concerns me is when all of a sudden you drop nitrogen on there and water on there. The plant will no longer be stressed, and if I had not sprayed it and have 3-inch, 4-inch weedy rice, how tall is that weed going to be in the next seven days?

“I assure you that you’re going to have difficulty controlling weedy rice post flood,” he added. “I want weedy rice at three inches or less when I’m trying to control it post flood — not 8-inch, 10-inch or 12-inch weedy rice that’s tillering. That’s why I come back to Provisia. My recommendation on Provisia is 11-10-10. That rate does not change regardless of environmental conditions.”

Concluding Remarks

Walker pointed out that situations do arise that can put you behind the eight ball. He recommends “growing the crop on paper” before the season begins and focusing on timeliness. Once the herbicide applications get off schedule, and the weeds are still growing, the snowball effect is huge with Provisia rice.

“Educating landlords and decision makers is probably a missing piece in the puzzle,’ Walker said.

The consensus among the panel members was that landlords are going to have to come to the realization that four or five years down the road rice will not be grown in these fields, considering today’s weedy rice populations. If landlords say they want to grow rice because it’s economically profitable, they have to understand it’s not going to be economically profitable four or five years from now if measures — such as rotating rice with soybeans — are not implemented right away.

Although this is one example of how to protect Provisia rice, consider following all the Best Management Practices to steward and hopefully save — or prolong — the life of the technology.

To learn more about Best Management Practices for Provisia Rice, visit https://www.horizonseed.com/news/best-management-practices-for-provisia-rice.

Carroll Smith is the associate publisher and editor-in-chief for One Grower Publishing magazines.

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