Soybean South April 2020

ONE GROWER PUBLISHING, LLC

APRIL 2020

3 reasons to change preplant dicamba burndown use

Not as bad as you think Let’s rap about Dectes stem borer

APRIL 2020

ONE GROWER PUBLISHING, LLC

3 reasons to change preplant dicamba burndown use

Not as bad as you think

‘Most Crop Per Drop’ contest promotes water-saving efforts

Let’s rap about Dectes stem borer

CONTENTS 4 Not as bad as you think Let’s rap about Dectes stem borer in soybeans

6 3 reasons to change traditional preplant dicamba burndown use 8 Industry News Soybean business scene Cover photo by David Cappaert; Bugwood.org

DIGITAL EXTRAS

Soybean South: Covering Southern Soybean Production Soybean South is a supplement to the Mid-South and Southeast versions of Cotton Farming magazine and Rice Farming magazine.

It’s one thing to take top honors in yield contests, like Arkansas’ Grow for the Green, the Tennessee Top Bean Soybean Yield Contest or the North Carolina Soybean Yield Contest.

It’s quite another to place in the top three in Arkansas’ Most Crop Per Drop contest, since winners may not have the highest overall yield. Instead, they have the highest water-use efficiency and have squeezed the most bushels per acre from every acre-inch of rainfall and irrigation.

The top three soybean winners receive cash prizes as well as water-saving technologies donated by sponsors. The contest helps encourage growers to use technologies, such as moisture sensors, flow meters and surge valves, they might not otherwise try. Entrants Vicky Boyd also receive report cards that compare their water-use Editor efficiency to other contestants.

“Normally you don’t get any feedback about how good you’re doing, but this really tells you how you’re doing relative to your peers as far as water use,” says Dr. Chris Henry, University of Arkansas irrigation engineer. “When people get this (report), they get a real feeling for how they’re doing with their water.”

Last year, Arkansas received unusually heavy rainfall, which allowed producers to ease back on irrigation. Nevertheless, Poinsett County producer James Wray applied only 6.5 inches of irrigation, coupled with nearly 21 inches of rain, to produce about 113 bushels per acre. His water-use efficiency was 4.3 bushels per acre-inch of water.

As with many contestants, Wray entered in 2018 but didn’t win with a water-use efficiency of 3.09 bushels per acre-inch. He took what he learned and credits Pipe Planner computerized hole selection, sensor-based irrigation scheduling and variety selection for his improved water conservation. Before the contest, Wray relied on the old “experience” method for irrigation scheduling.

“This was my first year using sensors for irrigation timing in soybeans,” Wray told Henry. “I honestly didn’t trust them at first, so I would go check every time I thought I needed to turn the pump on. Based on my experience this year, I have concluded that I have been overwatering. I would have watered this field three additional times.”

Mississippi County producer Becton Bell was second with 88 bushels per acre and a water-use efficiency of 3.8 bushels per acre-inch. Cross County producer Clint Boles was third with a yield of 73 bushels per acre and a water-use efficiency of 3.5 bushels per acre-inch.

Now water-use efficiency is a prize that will yield rewards long after the cash award has been spent.

Vicky

Follow Soybean South on Twitter @soybeansouth

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Send comments to: Editor, Soybean South Magazine, 875 W. Poplar Ave., Suite 23, Box 305, Collierville, TN 38017 or email vlboyd@onegrower.com.

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Let’s rap about Dectes stem borer in soybeans

DAVID CAPPAERT; BUGWOOD.ORG

Not as bad as you think

By Scott Stewart

O

COURTESY UNIVERSITY OF TENNESSEE

ver the years and several times in the last month, I’ve had folks tell me how bad Dectes stem borer hurt their soybean yields. Almost without exception, they describe low-yielding spots in their fields and/or weak, dying and dead plants … and they found a lot of Dectes larvae in the stems. They are convinced the two are related and look at me like I’m crazy when I suggest they are not.

Here’s what I know.

Biology and pest status

} Dectes stem borer has multiple hosts, notably including ragweed and sunflower. } There is one generation per year. } They overwinter as larvae inside and at the base of stalks. Overwintering larvae will be at or below the soil level (very similar to southwestern corn borer in non-Bt corn). } Larvae pupate in the spring and adults emerge over a period of several weeks, typically during June in Tennessee. } Adults are strong fliers and can infest fields from a distance. } Adults prefer to lay eggs in plants that have a little size on them, often during R1-R3 growth stages of indeterminate soybean varieties.

You will definitely see where the adults pick on varieties that are at the right growth stage when they emerge. } Females can lay numerous eggs during her life, but she deposits them singly inside a soybean leaf petiole in the mid and upper part of

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the canopy. There may be several different eggs laid on a single plant. } Larvae spend there entire life inside of the plant, first tunneling within the leaf petiole and then entering the main stem. Thus, foliar insecticide applications may kill adults but have little or no effect on larvae. } The leaves of infested petioles will eventually turn brown and drop from the plant at about the time the larva moves into the stem (see upper right picture). Thus, they do cause some minor defoliation. } By the time the larvae is full sized, it has tunneled inside the stalk all the way to the base of the plant where it will spend winter. The larvae typically mature about the same time as the soybean plant. It may be hard to believe, but data showing that this tunneling directly SOYBEANSOUTH.COM

COURTESY UNIVERSITY OF TENNESSEE COURTESY UNIVERSITY OF TENNESSEE

affects yield is hard to come by and questionable. Indeed, our data indicates no yield loss as a result of stem tunneling (see middle photo to the right). } Larvae are cannibalistic, so you rarely find more than one mature larva per plant. } In preparation for overwintering, the larvae often girdle the stem near the base of the plant by chewing around its circumference (from the inside). Thus, some stems may break and lodge before harvest.

This injury can cause yield loss, mostly by reducing harvest efficiency. Do not confuse this with “regular lodging” where the plants simply lay or bend over.

With Dectes, there will be a relatively clean break at the site of the girdle, and the larvae will be present in the stem below the break. } Any lodging that occurs is unpredictable, and significant levels are only rarely seen before fields are harvested. No one fully understands why lodging occurs in one field and not another, even though both are heavily infested. It sometimes appears variety related, but I’ve not been able to replicate that observation in test plots. I’ve left heavily infested soybean stand for many weeks after they were ready to harvest without seeing significant lodging, and then you see that rare field where the opposite happens. } In short, the potential for meaningful yield loss is from lodging, which is relatively rare and unpredictable. I’ve tried and have not been able to replicate the conditions that cause this.

50% to 90% in some years. } You generally can’t spray insecticides timely and often enough to provide good control because the adults come out over several weeks and lay eggs that are protected within the plant. It’s even less effective when there is high pressure. Thus, insecticide applications are typically not cost effective (and not recommended). } One caveat here: There is some data showing applications of chlorantraniliprole (Prevathon or Besiege), at least at high rates and when repeated, can kill the larvae. But it’s very questionable whether this is cost effective, and again, not recommended. It’s an expensive option considering meaningful lodging occurs in a small percentage of fields. } In summary, foliar insecticide applications are not recommended because they don’t work well, and anyway, the risk of lodging in low.

Don’t fool yourself!

I’ve never seen a Dectes stem borer kill a plant. If your plants are turning brown or withering, there’s a good chance you are dealing with a pathogen like stem canker, anthracnose, charcoal rot or taproot decline. I’ve walked many heavily infested fields where the grower points out how many Dectes there are in the “bad spot,” only to show them they were just as numerous in the good spots.

To reinforce my comments, I wanted to share some data collected some time ago in Tennessee, Arkansas and a couple of other locations. My colleagues, including Dr. Gus Lorenz, and I were testing an insecticide seed treatment (fipronil).

This insecticide is not and will not be labeled for use in soybean, but it does a good job killing the larvae before they do significant tunneling in the stems. As you will see in the table, we had high average infestation levels of Dectes across many trials.

The seed treatment provided good control, but yields were not consistently improved by it. We might have seen a yield response if significant lodging occurred in these trials, but it did not.

The take home is that stem tunneling had no obvious effect on yield. It’s apparent that the pith of that soybean stem is essentially dead tissue, so feeding by the larvae is not hurting the plant.

Dr. Scott Stewart is an integrated pest management specialist and entomology professor with the University of Tennessee. He may be reached at sdstewart@utk.edu.

Dectes Control with Fipronil IST and Yield Response * Location & Year

What should I do about Dectes stem borer?

} Given their biology, it is not surprising that Dectes populations are higher in no-till areas. Because they overwinter in the base of plants, tillage can kill overwintering larvae. However, this will have considerably less impact in no-till areas unless it is done across a large area because adults can readily infest from neighboring fields or from weedy hosts. And of course, tillage is not a good production practice for many fields in West Tennessee. } Most importantly, harvest heavily infested fields as soon as they are mature to reduce the chance of significant lodging. Unfortunately, by the end of the season, many fields may be infested at levels of TWITTER: @SOYBEANSOUTH

% Infested Plts in Untreated Plots

% Reduction

By Fipronil

Average Yield (Treated, Untreated)

Yield Change (Treated Untreated)

Jackson, 2011

58

97

46.5, 44.1

2.4

Milan, 2011

73

98

32.8, 33.4

-0.6

Milan, 2010

13

90

48.5, 48.8

-0.3

Jackson, 2009

40

97

44.2, 42.8

1.6

Milan, 2009

29

79

66.9, 62.7

4.2

Jackson, 2008

58

85

44.8, 49.1

-4.3

Milan, 2008

82

86

42.0, 39.8

2.2

Milan, 2008

83

55

40.8, 40.6

0.2

Arkansas, 2008

59

64

45.1, 44.5

0.6

Missouri, 2008

50

73

38.3, 36.7

1.6

Jackson, 2007

70

86

—

—

Jackson, 2007

65

92

—

— 0.0

Arkansas, 2007

85

88

38.5, 38.5

Kentucky, 2007

70

90

30.0, 29.0

1.0

59.6

84.3

43.2, 42.5

0.7

Average

Fipronil is not labeled for use on soybeans and is not expected to receive a label.

*

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COURTESY UNIVERSITY OF TENNESSEE

Junglerice escaped a glyphosate plus dicamba burndown in Titpon County, Tennessee, in 2019.

3 reasons to change traditional preplant dicamba burndown use

By Larry Steckel

F

or the past two decades, dicamba has been used extensively as a preplant burndown on almost all Tennessee cotton and soybean acres. It was often used at 8 to 12 ounces per acre of a Clarity-type product 14 days before planting.

I know it has become tradition to use it in this fashion, but I believe this should be changed for three reasons. } First, the reason for all the dicamba use in a burndown was to target horseweed. At the time, it was a weed with no effective in-season herbicide option for control.

However, that is no longer the case. Most soybean and cotton acres in Tennessee are planted to an Xtend variety and the rest are planted to Enlist varieties. Depending upon which technology, horseweed can now be easily removed in crop with a dicamba, 2,4-D or Liberty application. } Second, it is becoming abundantly clear that the decades-long use of dicamba plus glyphosate as a burndown has selected for weeds that can survive and indeed thrive in that environment. Ryegrass, poa, junglerice, barnyardgrass and goosegrass are all now regularly escaping burndown applications of dicamba plus glyphosate.

I would suggest to go with glyphosate or glyphosate tankmixed with clethodim to have the best chance for success controlling these grasses before the crop emerges. Also consider using a residual that

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has good grass activity. Verdict would be a good option here as it has both burndown activity and grass residual. Others like Anthem Max, Dual Magnum and Zidua would also be good choices. } Third, from a financial standpoint, I would save the money on using dicamba before planting or even at planting as it will likely hinder grass control. In 2019, grasses often, and Palmer pigweed in some fields, escaped the initial post application of dicamba plus glyphosate.

As such, there were often second or third post applications needed to control those escapes. That money used on dicamba in the early burndown could be put to better use on those follow-up applications.

Recent greenhouse screenings of Palmer amaranth, junglerice and barnyardgrass plants grown from seed collected from those escapes in 2019 would suggest that grass and Palmer control will be even more of an issue this spring.

Finally, it is apparent that dicamba plus glyphosate has taken a step backward with respect to consistent control of many grasses and in some cases Palmer amaranth. Therefore, starting clean has never been more important. Gramoxone used right behind the press wheel will be the most important herbicide used on all our no-till soybean and cotton acres in 2020.  Dr. Larry Steckel is a University of Tennessee Extension weed specialist. He may be reached at lsteckel@utk.edu.

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I N D U S T R Y

While completing his master’s degree, Moseley worked for the University of Arkansas in Logan County as an Extension agent with agriculture and 4-H youth development responsibilities.

He can be reached at dmoseley@agcenter.lsu.edu or 318-4272663. His office is at the AgCenter Dean Lee Research and Extension Center in Alexandria.

■ Bayer has new postemerge herbicide in early development

Bayer has announced an herbicide molecule in Phase 2 of early development that has demonstrated effective control of key resistant grasses in research trials, according to a company news release.

The announcement comes at a time when an increasing number of weed species have developed resistance to multiple modes of action, leaving growers with fewer weed control measures in their toolbox.

Phase 3 covers late development, and Phase 4 involves filing registration packages with the U.S. Environmental Protection Agency and other countries’ regulatory bodies.

Should the product come to market, it would mark the first new postemergence mode of action for broad-acre weed control in 30 years. The last new family of herbicides were the HPPD inhibitors.

Each new herbicide takes at least 10 years and more than $250 million to bring to market.

Bayer has not yet announced a brand name for either the active ingredient or the individual products.

■ EPA registers new Valent herbicide premix

The Environmental Protection Agency has registered Perpetuo herbicide from Valent U.S.A. to control annual broadleaves and grasses in corn and soybeans.

The postemergence herbicide is a premix of pyroxasulfone, a Group 15, and flumiclorac, a Group 14. Together, they provide both burndown and residual control that can be used in combination with any soybean or corn trait system, according to a news release.

Weeds, such as waterhemp and Palmer amaranth, have a long germination window that can last through late summer, making them hard to control with a single preemergence application.

One reason why these weeds are so difficult to manage is that even if the emerged weeds are controlled with a burndown, germination can still occur prior to canopy closure. If weeds do emerge during this time, they compete with the soybean plant for water and nutrients, robbing it of yield potential.

This gap in coverage can lead to weed breakthroughs that can reduce yields by as much as 10%, according to the United Soybean Board’s “Take Action Herbicide Resistance Management Program.”

PHOTO COURTESY LSU AGCENTER

Dr. David Moseley

■ LSU AgCenter hires new state soybean specialist

The Louisiana State University AgCenter has appointed Dr. David Moseley assistant professor and state soybean specialist.

He has responsibilities for coordinating Extension soybean activities, including oversight of official variety trials and off-station variety core block demonstrations across the state.

With experience working with both industry and the public, Moseley says he looks forward to assisting soybean producers and supporting the industry by conducting research and sharing both new research results and existing research-based information.

“Choosing the best genetics is one of the most important steps to success for producers,” he says.

Moseley’s major projects will involve working with other AgCenter researchers and agents to aid on-station research and on-farm variety performance trials, and collaborate with experts in disease, insect and weed management.

He earned his doctorate from the University of Arkansas in crop, soil and environmental sciences, focusing on soybean breeding and genetics. He received his master’s degree in agricultural, food and life sciences from the University of Arkansas after completing his bachelor’s degree at Texas A&M University.

Before joining the AgCenter, Moseley was a production research scientist with Monsanto/Bayer in Nebraska.

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N E W S

■ AMVAC adds 4 herbicides to its porfolio

AMVAC plans to launch four herbicides for the 2020 season that it acquired last year from Corteva Agriscience.

The products are tankmix partners for a variety of primary herbicides used in the U.S. market, according to a news release.

• Classic herbicide expands the postemergence weed control spectrum in soybeans.

• FirstRate herbicide provides preemergence and postemergence control of key broadleaf weeds in soybeans.

• Hornet herbicide delivers postemergence broadleaf weed control of glyphosate-resistant weeds in field corn.

• Python herbicide allows flexible broadleaf weed control in soybeans and field corn.

■ Helena unveils 3-way herbicide premix

Helena Agri-Enterprises LLC recently introduced Antares Complete herbicide, a premix of three different active ingredients to offer preemergence residual control of a host of broadleaf weeds and grasses. Among its targets are pigweed, lambsquarters, common ragweed and cocklebur as well as those resistant to glyphosate and a number of other herbicide groups.

Antares Complete combines the active ingredients of metribuzin (Group 5), sulventrazone (Group 14) and s-metolachlor (Group 15).

The premix manages early weed competition in all soybean cropping systems with long residual control, according to a news release.

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