Ultraviolet-C irradiation has no short-term, direct effects on cyclamen mite (Phytonemus pallidus (Banks)) in strawberry

Abstract

Cyclamen mite is a nearly global pest of strawberry, inhabiting concealed spaces within folded leaves and flower buds emerging from plant crowns. It feeds on new plant tissue causing leaf discoloration and deformation, stunted plants, fruit bronzing and cracking, and yield losses at high population levels. Because ultraviolet-C (UV-C) irradiation is a promising new tool for disease and pest management in strawberry, and because there are few control options for cyclamen mite, we tested the direct, short-term effects of UV-C on cyclamen mite populations in potted strawberry plants in a controlled environment. Results from three experiments showed few differences in cyclamen mite populations on controls versus plants treated with UV-C (0.237 W m−1) for 3 or 4 weeks. In the second experiment, using a different strawberry cultivar and directing the UV-C from above the plant crown only, there was indication of a mild effect that may be due to some direct mortality and/or indirectly to plant defenses. However, longer-term studies will need to be conducted to determine whether pre-infestation exposure to UV-C can enable strawberry plants to better resist or tolerate cyclamen mite populations. Direct mortality did not occur as in previous experiments with pests, like twospotted spider mite, that live primarily on opened leaves.