early season peanut disease control

UNIVERSITY OF GEORGIA Plant Pathologist Tim Brenneman explains early season peanut disease control.

Early-season disease control keeps peanut yield foe at bay

• The old yield-robbing foe that has popped up with too much regularity from Georgia to Mississippi over the past three years is white mold. • Caused by the fungi Sclerotium rolfsii, white mold, or Southern stem rot, as it is often called, came on late in the season and kept statewide yields across the belt from setting the record yield bar even higher.

The 2012 peanut production season was literally one for the record books, with growers throughout the U.S. making record-high yields and production. Having accomplished such a feat, many in the industry are asking, “What’s next?” For the answer to this question, it’s important to take a look at what is in the peanut research pipeline — those problems, issues and initiatives currently being addressed that will lead to even more efficient and profitable peanut production. The “Pipelines to Peanut Profitability” series takes an in-depth look at these areas of research, what they could mean to growers, and when producers can expect to see practical, on-farm applications of this research.


Last year was the first time in history the Southeast peanut-producing region averaged two tons per acre — an indication diseases were kept under control, but an old disease nemesis came on strong late in the year to take some of the luster off the record-breaking crop.

The old yield-robbing foe that has popped up with too much regularity from Georgia to Mississippi over the past three years is white mold.

Caused by the fungi Sclerotium rolfsii, white mold, or Southern stem rot, as it is often called, came on late in the season and kept statewide yields across the belt from setting the record yield bar even higher.

Some contend white mold never really went away and has been a contributing factor in keeping peanut yields in the 3,000 pound per acre range for several decades.

The trend in peanut yields is going up, but not always on a predictable schedule.

Back in 1967, peanut researchers and growers alike reveled in the country’s first 2,000 pound average yield peanut crop. Just as they are doing now, growers back then were clamoring for the next frontier in peanut yields.

Improvements in weed management technology, new highly efficacious, easy-to-use fungicides and a renewed interest in peanut research quickly pushed that frontier to a new level.

Within seven years the average peanut yield in Georgia, perennially the country’s top peanut producing state, reached 3,000 pounds per acre.

Again, growers clamored for more.

Changes in the politics of peanuts, changing weather patterns, and some contend just plain bad luck kept peanut yields in the 3,000-4,000 pound per acre range for 39 years, with growers finally making it to the 4,000 pound average last year.

University of Georgia Plant Pathologist and UGA Peanut Team member Tim Brenneman, says the next yield frontier may come much quicker, pushed by improved varieties with better disease resistance and powered by growers willing to find ways to best apply the new technologies that are abundant.

“I remember three years ago, standing in a peanut field with a cooperating grower and how excited I was to take pictures of the first three-ton per acre peanuts I’d ever helped grow.

Takes bigger yield now

“Now, you’ve got to go well over 6,000 pounds per acre to get excited enough to break out the camera and call the neighbors,” Brenneman says.

Will peanut farmers as a group be able to harness all the tools that are currently available and push on to the 5,000 pound per acre frontier in the next few years? One of the keys to answering that question is how well growers will be able to protect their peanut plants from diseases.

Brenneman, and other veteran peanut disease researchers, agree the tools are available to growers to manage peanut diseases well enough to significantly improve yields.

However, the occurrence and severity of the major diseases of peanuts has changed in the past few years and adapting the available tools to manage these diseases will be critical to pushing yields on up toward three tons per acre.

Some of the new Virginia-type peanut varieties have excellent disease resistance packages, and these will no doubt be critical in the battle against diseases.

New varieties like Bailey and Sugg from the North Carolina State University breeding program have excellent disease resistance.

However, Brenneman points out that most of the new runner type varieties and some of the new Virginia types are still highly susceptible to diseases, particularly to soil-borne diseases.

New varieties, new production practices, new fungicide technology and seemingly a new weather pattern may all be critical to how well growers are able to adapt to and most profitably apply disease management technology.

For example, in both Carolinas last year, there were more 90 degree days in March than in May and more rain fell in August than in April.

While few in the academic arena are ready to announce global warming is here to stay, all do agree weather patterns are changing and these different conditions will play a part in production of all crops, all over the world.

Peanuts are no different.

“Three years ago I spoke at the South Carolina statewide peanut meeting, and my main topic of discussion was CBR (Cylindrocladium black rot). This disease was a big problem in Georgia, and it was an even bigger problem in South Carolina and further north in the peanut producing belt,” Brenneman says.

CBR has been minor problem

“For the past few years, CBR, at least in Georgia, has been a minor problem. Don’t forget about CBR — it’s still around, but it’s not been nearly so much of a problem in recent years, he adds.

“Our biggest disease challenge in Georgia the past few years has been white mold. Not only are we seeing more of the disease in peanuts, but we are seeing it occur at much more damaging levels at much different times of the growing season than we used to see it.

White mold is a warm-weather craving disease. Historically, it has been considered a mid-to-late season problem, but that scenario has changed dramatically in recent years.

White mold is an historic pest of peanuts, but it’s been on the quiet side until recent years.

“The warmer early season temperatures in recent years have been particularly favorable for outbreaks of white mold, and historically white mold has been the most damaging of all peanut diseases, causing millions of dollars of loss to Georgia growers,” Brenneman says.

Currently grown cultivars are moderately to highly susceptible. Several effective fungicides are available, but they are expensive, and there are cases each year when disease control has not been as good as expected.

This occurs since Sclerotium rolfsii can grow extensively underground, and pods are a difficult target for a fungicide to reach. These fungicides are systemic but do not move down in plants.

“Night sprays, when peanut leaves are folded, and use of irrigation to wash fungicides off the foliage, have both improved disease control and yield,” he says.

Timing sprays is also important. Traditionally white mold sprays go out 60-100 days after planting. But early season hot temperatures, especially in 2010 and 2011, have allowed white mold to start much sooner on peanuts only several weeks old.

To combat this, a totally new concept in improving white mold control is the use of banded sprays early after emergence.

Back in 2010, Brenneman’s main focus was still on reducing CBR damage to peanuts.

Early emergence banding

As part of that effort he tried a system called ‘early emergence banding’ in which he uses Proline in a 40 gallon over-the-top spray, concentrated  in a 4-5 inch band.

That volume of water in the band is equal to 300-400 GPA broadcast, and was designed to  force a good volume of fungicide down to the root system of young peanut plants where CBR infections begin.

“Though our target was CBR, our initial test in 2010 showed dramatic reductions in white mold with one spray of Proline at 21 days after planting (a time when we normally do not even spray fungicide).

“Additional trials in 2011 showed significant yield increases. Results in 2012 were more mixed, probably due to the cooler early season temperatures, but several trials again demonstrated a strong yield response,” the UGA researcher says.

In addition to the target pest, CBR and white mold, the use of banded sprays early in the season also showed good control of leafspot, and lower spray volumes (10-20 gallons per acre) have done just as well as 40 GPA.

“We have learned more about how several different fungicides work in this type of early application, but there are still questions about use on twin row peanuts, spray volumes, etc.

“The main questions regard how to incorporate these early sprays in full-season fungicide programs to give the best economic return, and how they actuallycompare to simply broadcasting similar fungicides early in the growing season, Brenneman says. 

“Either way, preventing white mold before it begins is an important step toward obtaining the full potential of new high-yielding, but disease-susceptible cultivars like GA-06G,” he adds.

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Other articles in the series:

New, improved varieties leading way for U.S. production

X-ray vision points to more efficient peanut grading system

Water-use efficiency becoming priority for peanut producers who irrigate

Lack of nematicides slows use of variable rate application in peanuts

Taking guesswork out of determining peanut maturity





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