Violet light is the most effective wavelength for recruiting the predatory bug Nesidiocoris tenuis

Nesidiocoris tenuis (Heteroptera: Miridae) is a zoophytophagous mirid bug that is used as a biological control agent for agricultural pests including whiteflies. N. tenuis is mass-reared commercially and can be easily bred on banker plants. However, there are still difficulties in establishing populations on crops. Light illumination is a promising candidate for recruiting N. tenuis to crop plants. In this study, we investigated whether N. tenuis has a particular spectral preference using a six-arm arena equipped with six monochromatic LED lights: UV (365 nm), violet (405 nm), blue (450 nm), green (525 nm), orange (590 nm), and red (660 nm). Adult bugs were introduced into the arena, and phototactic behavior was observed. A greater number of male bugs chose violet light, whereas female bugs chose violet and UV light equally. We next examined the effects of violet illumination in a tomato greenhouse. In conventional plots, bugs remained near banker plants, whereas in illuminated plots, bugs immediately dispersed from the plants and became uniformly distributed in the greenhouse. Based on these results, we conclude that violet is a promising wavelength for the recruitment and establishment of N. tenuis on crop plants.