Potential of UV‐C for management of two‐spotted spider mites and thrips in Florida strawberry

BACKGROUND Major pests of Florida strawberry (two‐spotted spider mites, Tetranychus urticae Koch; chilli thrips, Scirtothrips dorsalis Hood; and western flower thrips, Frankliniella occidentalis Pergande) are difficult to manage using only conventional chemical control. Previous research has demonstrated high mortality of T. urticae eggs after exposure to ultraviolet B (UV‐B) light. Additionally, ultraviolet C (UV‐C) light has been shown to suppress powdery mildew in strawberry at doses between 85 and 200 J m−2 with no damage to the plant. Therefore, UV‐C may also have the potential to be used as an integrated pest management tool for arthropod pests of strawberry. The objectives of this study were to: (i) determine the effect of UV‐C on T. urticae, S. dorsalis, and F. occidentalis natural populations in open‐field strawberry; and (ii) determine the effect of UV‐C on T. urticae egg hatch after application in open‐field strawberry. Field studies were conducted during the 2019–2020 and 2020–2021 strawberry seasons in Florida, USA. Four treatments were compared: (i) foliar application of spinetoram in response to natural pest pressure; (ii) application of UV‐C 200 J m−2 twice a week; (iii) application of UV‐C 350 J m−2 twice a week; and (iv) a non‐treated control. RESULTS In the field trials, suppression of T. urticae was observed at 350 J m−2 in 2020–2021. In the other field trials, no effect was observed due to low natural infestations. No negative impact on yield was observed from UV‐C applications. CONCLUSION UV‐C shows promise as a component of an integrated pest management program for T. urticae in strawberry. © 2022 Society of Chemical Industry. Ultraviolet C light was effective to manage Tetranychus urticae populations in open‐field strawberry, but its performance was variable for thrips suppression when compared with spinetoram.