Progress being made against TSWV

Milton Parrott unwittingly drew attention to himself last year. He had one field with 50 percent stand loss due to tomato spotted wilt virus — the worst in the state, but certainly not the only producer to suffer losses at the hand of the virus. This year, however, he's drawing attention of a different kind, one that holds promise of an effective control measure for TSWV.

Parrott, who farms in Florence County, S.C., had just as soon not have the attention, but he's glad he sees some promise in the fight against the virus.

For Parrott, the problems with TSWV began last year. South Carolina producers in the southern part of the flue-cured belt, along the Georgia line, have been battling TSWV for years. On his 30 acres of flue-cured tobacco, Parrott this season has experienced a 40-percent loss to TSWV. So far this season, South Carolina has had its worst-ever bout with the virus. The virus has also wreaking havoc in the eastern part of North Carolina.

“I decided last year to turn over a field to Clemson to see if they could find something that would help,” Parrott said on the recent South Carolina Tobacco tour stop at his farm.

Now the attention comes from neighbors eager to learn how the research is going. “Everybody's real interested because we see some promise,” Parrott says. Research is also being done in the Walterboro, S.C., area.

In Clemson University research and Extension on-farm tests, Actigard, used in combination with Platinum and Admire, reduced TSWV incidence from 50 percent to 10 percent, says Bruce Fortnum, Clemson University Extension plant pathologist.

The results are promising to the point where researchers are seeking a 24C label for Actigard, which isn't currently labeled for the control of TSWV in tobacco.

In tests, “Admire and Platinum, combined with Actigard can reduce losses due to TSWV by about 40 percent,” Fortnum says. “Alex Csinos and Paul Bertrand (University of Georgia plant pathologists) have already turned heads with their work with Admire and Actigard.

“While 10 percent loss due to TSWV is still high, it would bring it down to a level where farmers could manage the disease,” Fortnum says.

Fortnum says Actigard has an “additive effect” in the control of TSWV incidence in tobacco. “Admire and Platinum suppress TSWV, but when you add Actigard, it makes the control that much better. We think Actigard would be a valuable tool for farmers to have.”

Parrott says he'd welcome something that works. “This year I've got about 40 percent incidence in my fields.”

Fortnum says farmers may view the additional expense of controlling TSWV as being “cost-effective.

“When you have disease losses as high as 50 percent, the application of a product that can cut disease levels by as much as 40 percent will more than pay for itself,” Fortnum says.

In the state during the South Carolina tobacco tour, Alex Csinos, University of Georgia plant pathologist, pointed out the complex nature of the virus. “It seems to change every year.”

On another promising front, Albert Johnson, Clemson University Extension entomologist, reports one breeding line “has shown by far the best resistance to thrips or the virus” in South Carolina.

The South Carolina Tobacco Board saw the problem with TSWV coming and funded the research, Johnson says. In the variety tests, 45 entries had 60 percent incidence of the virus; 12 entries had less than 20 percent incidence; and the promising breeding line had only 3 percent incidence.

“We've got our fingers crossed for that one breeding line,” Johnson says.

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