2022 Volume 31 Issue 1 Pages 1-11
Artificial ultraviolet-B (UV-B) radiation is lethal to the two-spotted spider mite Tetranychus urticae. Recent studies in greenhouse strawberry have shown that light-reflecting sheets installed under strawberry plants can increase the suppressive effect of UV-B on T. urticae by reflecting the UV-B delivered from overhead lamps to the underside of the leaves. These methods are expected to be complementary to biological control methods, such as phytoseiid mites. However, light-reflecting sheets have low water permeability, which can result in the formation of puddles after pesticide spraying, leading to fruit deterioration and loss of yield. It is important to explore highly efficient installation methods for light-reflecting materials (LRMs) in spider mite control. Here, we examined the effects of three LRMs, and the impact of LRM orientation (horizontal vs. vertical), on T. urticae populations in greenhouse strawberry treated with UV-B radiation, chemical pesticides, and biopesticide control with phytoseiid mites. Of the three LRMs examined, a reflective 0.6 × 0.6-mm-mesh polyethylene net (“Mushi Furatto Net”) and a 2.0 × 7.0-mm-mesh polyethylene net woven with flashspun nonwoven fabric sheets (“Slimwhite 75”) offered significantly increased suppression of T. urticae populations compared with white mulching sheet alone. Even though these LRMs were installed horizontally, they were little stained at the end of the experiment, suggesting that puddle formation after pesticide spraying was avoided.