Abstract: To achieve precise control of tobacco scarab beetle damage, a fixed-point trapping method was employed to investigate the attraction effects of four light spectra on adult scarab beetles in tobacco fields of Weining County, Guizhou Province, as well as their safety for major beneficial insects. The characteristics of the four tested light spectra were as follows: 1#, 330-420 nm, with peak wavelengths at 350 and 370 nm; 2#, 330-600 nm, with peak wavelengths at 350, 380, and 560 nm; 3#, 570-680 nm, with peak wavelengths at 605, 628, and 650 nm; 4#, 330-490 nm, with a peak wavelength at 350 nm. The results showed that the attractiveness of the four light spectra to adult scarab beetles followed the order of 2# > 4# > 1# > 3#, with spectrum 2# exhibiting the highest attraction effect. Spectrum 2# attracted the greatest number of three key scarab beetle species: Maladera verticalis, Maladera ovatula, and Maladera orientalis, with a cumulative total of 1 693 individuals, accounting for 26.19% of the total insects trapped by this spectrum. Spectrum 4# ranked second, trapping a total of 1 215 individuals, representing 26.80% of its total catch. The safety analysis showed that spectrum 2# had the lowest beneficial-to-harmful insect ratio, with a value of 0.016. Analysis of phototactic rhythm revealed that the nocturnal phototactic activity of scarab beetles was mainly concentrated between 20:00 and 24:00. The highest number of the three key scarab beetle species was trapped during 22:00-24:00 (187 individuals), followed by 20:00-22:00 (96 individuals). Comprehensive analysis indicated that spectrum 2# demonstrated the optimal attraction effect for scarab beetle pests and key species, along with the lowest beneficial-to-harmful insect ratio, indicating good safety for application in tobacco fields. The optimal trapping period was recommended to be from 20:00 to 24:00.

Key words: tobacco field, scarab beetle, light spectrum trapping, beneficial-to-harmful insect ratio after trapping, phototactic rhythm