Incidence of spotted wilt is on the increase; take steps to reduce thrips pressure and risk to this disease.
In the early days of ESPN’s SportsCenter, the anchors developed clever catch phrases to connect with the audience. One of those anchors, Dan Patrick, would inevitably say at least once during a broadcast,
“You can’t stop him; you can only hope to contain him.” That’s how the University of Georgia’s peanut researchers want producers to think of Tomato Spotted Wilt Virus.
“Tomato Spotted Wilt Virus never went away,” says Bob Kemerait, UGA Extension plant pathologist.
“We can’t eliminate the disease; all we can do is manage it and take steps to reduce the risk.”
Upward Trend In Losses
In 2016, losses to tomato spotted wilt (TSWV) were estimated to be 3.5 percent, which is slightly up from the 3 percent loss in 2015.
Kemerait says that although losses to TSWV have been low in many fields, there were significant losses in some fields.
“This disease continues to be a potential threat to peanut production and growers must continue to incorporate the lessons spelled out in Peanut Rx to minimize the threat from this disease,” he says.
Shorter rotations and a very warm winter are two primary reasons both Kemerait and UGA Extension entomologist Mark Abney are asking producers to be diligent against TSWV and thrips, the vector or carrier of TSWV.
It’s About Reducing Risk
While increased thrips pressure does not necessarily translate into increased TSWV, Kemerait advises leaning towards making good, strong management decisions for reducing the risk of TSWV through the use of Peanut Rx and in reducing thrips pressure.
The impact of direct thrips feeding on yield and time to maturity is not well understood, but minimizing crop stress is an important consideration in making thrips management decisions, says Abney.
“Everyone that puts a peanut in the ground will have thrips. How bad are they going to be? I’m not sure and neither is anyone else. However, they might be more significant this year because of the weather.”
Abney says since he moved back to Georgia in 2013, there has been moderate-to-high thrips pressure in peanuts in Georgia.
“It is important that we continue to use the recommendations found in Peanut Rx for reducing thrips pressure and TSWV,” Abney says. “Phorate or Thimet is still the only insecticide that has been shown to reduce TSWV incidence in peanut, and it provides good protection against direct feeding damage.”
Abney also says an in-furrow application of liquid imidacloprid has shown good efficacy against thrips in a number of university trials in recent years. However, he says, peanut seed treatments do not provide adequate thrips suppression in years with heavy pest pressure.
Once again, producers should know that insecticides will not be completely effective 100 percent of the time, and it is common to see some thrips feeding injury on peanut seedlings regardless of what at-plant insecticide is used.
No Decision Is A Decision
As Abney says, there is no such thing as doing nothing for thrips and spotted wilt. “Every decision you make when you plant peanuts affects thrips and TSWV from the day you plant, to the variety you select, to the row pattern, to seed spacing – it all affects thrips and TSWV and it’s all covered in Peanut Rx. Everything has an impact on thrips and TSWV in one way or another.”
For planting window, the University of Georgia recommends that growers consider planting a portion of their peanut crop in the latter part of April. Spreading the peanut crop over April and May offers many advantages to peanut producers. Although there continues to be increased risk to tomato spotted wilt for peanuts planted in April, this risk can be reduced by planting newer, more resistant varieties.