Three of these critical problems can only be tackled at planting.
⋅ BY AMANDA HUBER ⋅
One of the greatest mystery novelist’s later works in her series of Hercule Poirot stories is The Big Four. In this story, Agatha Christie has Poirot looking for four criminal masterminds of an international crime syndicate. Solving the mystery involves faking his own death to draw in The Big Four. As always, the criminals are no match for Poirot’s “little grey cells,” and he dispatches them into the underworld obscurity.
According to University of Georgia Extension plant pathologist Bob Kemerait, the peanut crop has its own Big Four: Tomato Spotted Wilt Virus, seedling disease, nematodes and the fungal diseases leaf spot and white mold. In production meetings this spring, Kemerait referred to these as the four horsemen of the apocalypse, a Biblical reference to the harbingers of the end times. Any way you look at it, these four are critical threats to the peanut crop with the potential to kill the plant quickly or rob yields in the end. The only time to combat three of these problems is at planting, something that can be overlooked at the time.
Get Ahead By Looking Back
The first and most primary way of decreasing disease and nematode potential is with crop rotation. By increasing the interval between peanut crops in a field and planting crops that are not susceptible to the same diseases, growers can reduce the impact of diseases and nematodes and also reduce the reliance on chemical control methods.
The UGA recommendation is that peanuts are planted not more than once in a field over a three-year period. Growers should have a minimum of two years between each peanut crop. Short rotations lead to increased damage from disease and nematodes and increased yield losses.
Beyond rotation, Kemerait says growers should not focus too far ahead at planting. “I think we tend to white mold or leaf spot and get ahead of ourselves,” he says. “There is a lot that happens before then, and if you miss that opportunity, there is no going back.”
Looking ahead will overshadow the fact that this season started the previous year.
“When did the 2024 peanut season start? The answer is it already did,” Kemerait says. “The 2024 peanut season started with hot and dry conditions in 2023, which predisposes the crop to infection by Aspergillus fungi, A. flavus and A. niger. The fungus is already there.”
Other seedling diseases, such as Aspergillus crown rot and those caused by Rhizoctonia solani, are also a possibility, especially if those diseases have been a problem in that field before.
A fungicide seed-treatment, such as Rancona VPD, Rancona VPL or Trebuset, are seed treatments to help ward off these seedling diseases and get the crop off to a good start.
Spotted Wilt Still A Threat
Tomato spotted wilt is another disease that can only be reduced with decisions made at or before planting. Losses to TSWV in 2023 are estimated at around 5%, although it was much greater in some fields, but this is down from 7% in 2022. The factors affecting TSWV have long been identified but continue to be improved upon in Peanut Rx.
“Key considerations are planting date, variety selection and choice of at-plant insecticide,” Kemerait says. “Updates for 2024 include new varieties and point adjustments, as well as an update on Classic herbicide by UGA Extension weed specialist Eric Prostko.”
Specifically, growers can reduce their risk to losses from TSWV by planting resistant varieties. Newer varieties offer more resistance to TSWV than Georgia-06G, and growers should consider planting additional varieties on a few acres as a personal on-farm trial. Next, growers can further reduce their risk planting after May 10. Seeding rate, tillage, single rows versus double-rows, choice of at-plant insecticide and use of Classic herbicide are also points to consider. While it is difficult to follow all the management tactics outlined in Peanut Rx, growers can select the combination of a few that best fits their operation and offers some TSWV protection. All these decisions need to be made before planting.
“Once the furrow is closed, the die is cast for management of TSWV,” Kemerait says. “If you don’t do what you can before closing the furrow, you might regret it the rest of the season.”
In The Furrow
Kemerait says if you are trying to do everything you can to combat diseases and nematodes, don’t forget the in-furrow fungicides. Each have their own strengths.
As for options, Azoxystrobin is inexpensive and effective against some important fungal pathogens, especially Rhizoctonia. It is less effective against Aspergillus crown rot. Likewise, Abound or Quadris will enhance stands, improve vigor and is also good on Rhizoctonia but not Aspergillus crown rot. Proline offers some stand and vigor benefits and has activity against early season white mold and Cylindrocladium black rot, another disease that has no curative fungicides for in-season use. Velum in-furrow is also an option for the suppression of nematodes, Aspergillus crown rot, early and late leaf spot and white mold.
Other options for nematodes include: Telone II, AgLogic, Velum Total, Propulse, Vydate CLV and Return XL.
Kemerait says not all fields need an in-furrow fungicide at planting, but it is extra insurance to getting the crop off to a good start.
“Growers who plant high-quality seed, have a good rotation system and are careful about planting dates and conditions, may not need an in-furrow fungicide,” he says.
Fungal Disease
Weather conditions will dictate the type and severity of fungal disease in the coming season. In 2023, white mold was generally more severe than in 2022 because of the hotter conditions. Leaf spot is something growers can expect every year, with some years being more severe than others.
“Factors that increase threat to leaf spot diseases include environmental conditions, which also affects grower’s ability to make timely fungicide applications,” Kemerait says. “To prevent losses to leaf spot, especially late leaf spot, it is imperative to a) stay on a timely, proven program, and b) select fungicides or mixtures of fungicides based upon threat of disease in the field, and c) continue appropriate management programs through the end of the season.”
He also says that with peanuts staying in the ground for more than 140 to 150 days, more attention needs to be given to protecting the crop from white mold even after the traditional “four-block- 60-to-104-days-after-planting” window ends.
There are many fungicides and tankmixes that can be used against both soilborne and foliar diseases throughout the season. This one of The Big Four has copious options. However, once the furrow is closed, growers can only watch what happens in their crop from the other three: TSWV, nematodes and seedling diseases. PG
