UV system means ‘lights out’ for strawberry pathogen

When the light goes on, it’s lights out for a ruinous strawberry pathogen. Just imagine this: Pulling an ultraviolet lamp behind a tractor out into your farm in the middle of the night, pointing the UV light at the strawberries and zapping powdery mildew right out of the leaves and fruit.

That’s the idea behind new research led by UF/IFAS plant pathology Professor Natalia Peres. A new study she led shows that UV light kills powdery mildew, a disease that can significantly damage strawberries.

“UV treatments applied once or twice weekly were as effective as the best available fungicides applied on similar schedules for control of strawberry powdery mildew,” Peres said. “It’s not a one-time fluke.” The UV equipment has to be custom-built, but the cost is much lower than that of sprayer equipment, and there is no additional cost other than labor after the unit is built, she said. Since UV applications have to be done at night, Peres and her team have been collaborating with Saga Robotics from Norway on a UV robot-like system that could reduce the labor cost.

Benefits of the UV light system come as good news to strawberry farmers. UF/IFAS economic research shows strawberries are about a $300 million-per-year industry in Florida. Similar trials are being conducted across North America and Europe by the research collaborators on crops such as grapes, hops and cucumbers, Peres said.

“While research on these crops is still under way, UV applications seemed effective controlling powdery mildew in all cases,” she said. For the study, published in the journal Plant Disease, Peres worked with a global group of scientists to study how to use UV light to suppress plant pathogens.

The team designed a tractor-drawn machine with several UV lamps. A breakthrough in the research took place when Norwegian researchers discovered that the treatments were more effective when applied at night, Peres said. Powdery mildew develops resistance to many fungicides. It has also evolved to survive natural UV in sunlight, Peres said. But part of that adaptation to sunlight resulted in the pathogen not being able to repel UV light at night.

Additional tool
So, they applied the UV light to bypass the natural defenses of the pathogen. That method catches the pathogen napping, she said.

“Strawberry growers have to deal with several diseases and pest issues throughout the season and need as many tools as possible to manage them,” Peres said. “UV can be one of these additional tools that can help our growers manage powdery mildew with reduced fungicide input.”

UV lamps are widely used in water purification and microbiological sterilization, according to scientists on the research team. Until now, they have not commonly been used for plant-pathogen suppression in open fields, but Peres and her team showed the system works.

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