Effect of Spectral Sensitivity and Light Intensity Response on the Phototactic Behavior of Exolontha castanea Chang (Coleoptera: Melolonthidae), a Pest of Sugarcane in China

Abstract

The phototaxis of insects is closely related to light source factors, such as spectrum and light intensity. The cane grub, Exolontha castanea Chang (Coleoptera: Melolonthidae), is an important underground pest of sugarcane in Guangxi province of China. To clarify the effect of spectral sensitivity and light intensity response on the phototactic behavior of E. castanea, the phototactic behavior responses of male and female adults to 13 monochromatic lights in the wavelength range of 365–630 nm and different light intensities were measured. We found that both male and female adults had positive phototaxis to 13 monochromatic lights. The phototactic response rate of males and females at ultraviolet and violet light was the highest in the wavelength range of 365–420 nm. Among them, the most sensitive spectrum of females and males was at 365 nm and 420 nm, respectively. From the intensity response of phototactic behavior to different spectrum, the G1 (strong phototaxis) response rates of females at 365 nm and males at 420 nm were the highest. In addition, the phototactic response rate of females and males increased with the light intensity, showing a significant positive correlation. This study showed that the spectrum and light intensity were the key factors affecting the phototactic behavior of E. castanea. The sensitive spectrum of males and females were different, with a similar trend in phototaxis.