Spotted Wilt Warning

Losses nearly double that of prior year.

• By Amanda Huber,
Editor •

tomato spotted wilt symptoms
Tomato spotted wilt

Without appropriate management strategies, tomato spotted wilt virus has the potential to become widespread again, says University of Georgia plant pathologist Bob Kemerait.

“I would say that 2019 was a wake-up call. It’s an alarm going off,” he says. “In 2020, I’m encouraging growers to recognize that we had a significant problem with spotted wilt the past year.”

Manage Before Planting

Although disease levels were not what they were in 1997 when the crop’s value was reduced 10%, the potential is there for the virus to become widespread again if producers don’t consider appropriate management strategies, Kemerait says.

“Because of new varieties and other management options, we’ve been able to keep this disease at bay. But it is still here, and we need to be vigilant and protect against it.”

Kemerait cautions producers to think about tomato spotted wilt virus early on. All spotted wilt decisions must be made prior to or at planting. After planting, the producer cannot change those early decisions that affect the next 140 days.

“When the furrow is closed, planting date, variety, tillage, seeding rate and any in-furrow insecticide for thrips management has been decided on. At that point, you must live with it for the rest of the season,” he says.

Preferred Insecticide

Tomato spotted wilt is vectored by thrips. While it should follow that controlling thrips populations should effectively reduce the spread of TSWV, most products have been ineffective in suppressing the primary infection. Despite this, the Peanut Disease Risk Index recommends the use of phorate.

whole plant typical symptoms
Whole plant showing typical syptoms

“Phorate (Thimet) applied in the furrow at planting reduces thrips feeding injury and is the only insecticide that has been proven to reduce the incidence of tomato spotted wilt in peanut,” says UGA Extension entomologist Mark Abney. “The risk of thrips injury and spotted wilt infection is highest for peanuts planted prior to May 10.”

Additional Options

Abney says applying imidacloprid as a liquid in-furrow at planting has gained popularity over the past few years. This treatment can generally keep thrips injury from becoming severe when used at recommended rates, he says.
Another approach is no at-plant insecticide and instead a foliar application, usually of acephate, if needed to reduce thrips populations.

“This approach can work and save money, but it carries additional risks compared to in-furrow insecticides,” Abney says. “Weather conditions and other farm activities such as planting can make it difficult or impossible to apply foliar insecticides in a timely manner. A foliar insecticide that is applied too late provides no benefit.”

Turn Back The Trend

In 2019, losses to tomato spotted wilt across the Southeast were estimated at 7%, a significant increase from 2017 and 2018. A warm spring may account for some of the increase in thrips early in the season. For this year, producers are encouraged to carefully consider those factors that reduce the incidence of TSWV to determine what varieties, practices and products could be used to turn back this trend.

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