Further optimization of the UV-C strategy in strawberries

Further optimization of the UV-C strategy in strawberries


Mildew control with UV-C in strawberry is already well documented where the application of repetitive treatments can achieve a remarkable disease control. UV-C light causes DNA lesions that are lethal for mildew. In a new trial we further optimized the UV-C strategy.


Same application, different ‘dose-label’

From now on we will use a new way of referring to the doses used in the trails. The dose as referred to in the past is a minimum dose. After some measurements and calculations we decided to give the doses new ‘labels’. These new labels represent the maximum dose plants receive (measured at 167,5 cm from ground, point where highest intensity between lamps is reached at 20 cm from UV-lamps). In Table 1 an overview is given for each speed of the UV-robot. 


UV-C control equals IPM strategy for mildew control

In a spring cultivation in the plastic greenhouse the effect of UV-C radiation was tested on Elsanta plants divided into nine objects in four repeats. A group of untreated plants and a group of plants subjected to an IPM strategy serve as references. From previous trials at PCH we decided to focus on nighttime UV-treatments due to increased disease control (see previous news items Nov ‘18). The objective of this experiment is to determine the effect of UV-C on both Botrytis and mildew. We also investigate the possibilities of lowering the UV-C dose and the effect of two treatments a week instead of three. To further optimize application efficiency we compared one application of 110 J/m2 (only a single UV-C application when the robot moves forward through the crop) with two times 55 J/m2 (double UV-C application when the robot moves forward and backward) both resulting in plants exposed to the same total dose. To increase disease pressure, we inoculated three times with Botrytis cinerea. For powdery mildew we relied on a natural disease incidence. The UV-C treatments took place after sunset on Monday, (Wednesday) and Friday.


Results reveal that for Botrytis no overall trend can be seen in the different measurements of fruit rot. We therefore conclude that the effect of UV-C on Botrytis in these applications is rather minimal. Next, the UV- C doses applied did not influence crop yield. Production and grading is the same in all objects. Figure 1 shows the effect of UV-C on powdery mildew in the different objects. Mildew control is achieved with all applications of UV-C. No significant differences are observed between the plants subjected to different UV-C treatments. A UV-C treatment can equally control mildew as the conventional IPM strategy. In this trial no differences were found between the two times applications and the three times applications a week. Also no difference in infection rate is observed between the single- and double treatments (110 J/m² versus 2x 55 J/ m2). These results give opportunities to optimize the UV-strategy for the UV-robot. Under medium pressure mildew conditions, such as this spring cultivation, two treatments a week can be sufficient.


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