The Dragon: UV Light for Disease Management

In 2015 as part of a Cornell University project in collaboration with the University of Florida, Mark Rea and his team at RPI’s Lighting Research Center (LRC) designed “the dragon”, a tractor-pulled implement that delivers precise doses of UV-C light to replace the use of fungicides to fight powdery mildew in strawberries.  In 2017 they sought NYFVI funding to bring this novel light-based approach to summer squash.

The review panel and the board of directors were intrigued by the concept and liked the DIY plans that were proposed as part of the project.  If the approach proved efficacious they wanted to make sure it would be available quickly.  The proposal was funded.

Based on the Florida strawberry project, the LRC team knew UV-C light would kill powdery mildew. Based on work by colleagues in Norway and Cornell they also knew a lower dose could be used (enabling faster speeds) if the light was delivered after dark, to avoid the DNA repair mechanisms that are activated by blue light from the sun.

What they didn’t know was the optimum amount and duration of exposure that would allow the squash plant to thrive while killing the pathogen.  In order to keep the new approach as cost effective as possible, the target goal was to follow the typical spray schedule with once a week dosing.  Based on the lab work, it appeared this would work.

But, as farmers and researchers know, results are sometimes different in the field. While weekly dosing demonstrated some control of the disease, unlike with its use in Florida strawberry fields, it was no better than the fungicidal treatments.  One possible reason is the structure of the squash plant with its large leaves. Another factor was that the disease severity was high for all three conditions (untreated, fungicide and UV-light), suggesting that the disease control procedures may have been applied too late.

Past NYFVI board member, Larry Eckhardt and his son Andrew were actively involved with the research trials which took place on their farm in Stephentown. Kinderhook Creek Farm is a diverse vegetable and field crop operation which grows both organic and conventional crops, primarily for the wholesale market.

“This approach offers some clear advantages.  While the light needs to be delivered at dusk, unlike pesticides, the wind and rain doesn’t interfere with the schedule.  Additionally, there are no concerns about treatment immediately prior to harvest” said Larry.

He continued “I really liked the DIY aspect of the project. My son Andrew was able to follow the plans and build the dragon that was used for field trials in less than a day.”

Downy Mildew. The project had a second component which was to understand the effect of UV-C light on the equally vexing pathogen downy mildew in the lab.  They learned that, unlike powdery mildew, light dosing wasn’t as effective to fight the downy mildew pathogen once it was present.  However, it was very interesting to learn that prophylactic light dosing may stimulate a defense response in the plant allowing it to fight the downy mildew pathogen.

In 2019 the LRC team received NYFVI funds to test the prophylactic approach in cucumber fields. That work will be trialed in the summer of 2020.

Next steps: LRC submitted a 2020 NYFVI proposal to continue their work in summer squash. Their hope is to incoproate leaf agitation into the dragon, and examine the impact of starting earlier in the season with more frequent dosing.  The proposal also seeks to evaluate the “unintended consequences” of the UV-C approach.  Some of the collaborators believe that the dosing may be controlling not just powdery mildew, but also downy mildew and angular leaf spot disease! Since UV-C is a well-established germicidal modality, it is expected to be lethal to a wide range of bacterial, fungal and viral diseases. The ability to translate this capability to agriculture is dependent on the right design, field conditions, dose and schedule. Just like the large investment of prior approaches using chemistry, UV-light optimization represents another approach to integrated pest management.

More information and the plans to build the dragon can be found here.

Larry Eckhardt and his son Matt at a safety training held at their farm. Not pictured is Andrew Eckhardt who built the implement for field trials in the farm’s machine shop.