Abstract: 【Aim】Grapholita molesta is an important and frequent pest of fruit trees. This study aims to investigate the roles of light intensity on the oviposition preference of G. molesta, and to further reveal the dim-light vision ability in G. molesta. 【Methods】The numbers of eggs of G. molesta laid on leaves on the sunny side and shaded side in the peach tree canopy were investigated in spring, summer and autumn, and the difference in light intensity between the sunny side and shaded side at sunset was measured. Light-dark two-choice experiments were carried out indoor to test the oviposition preference behavior response of G. molesta adults to light intensity. 【Results】 In spring, summer and autumn, G. molesta adults preferred to lay eggs on leaves on the sunny side in the peach tree capony with significantly higher light intensity, the numbers of eggs laid on the sunny side were 4.24, 9.30 and 5.82 times as high as those on the shaded side, respectively. In the light-dark two-choice experiments, G. molesta adults preferred to lay eggs to light than to dark, with the oviposition selection rates of 87.48%, 83.68%, 82.92%, 80.08% and 84.84%, respectively, under 10 000, 100, 1 and 0.01 lx and natural light conditions. The oviposition preferences between to strong light and to weak light revealed that when the light contrast (strong light/weak light) was 10 and 2, respectively, G. molesta adults showed a preference to strong light under 10 000, 100, 1 and 0.01 lx and natural light conditions. Moreover, this preference to strong light did not decrease significantly with the decrease of light intensity, and the oviposition selection rates were higher than 75%.【Conclusion】 Light intensity can affect the oviposition preference of G. molesta adults. Female adults show obvious oviposition preference to strong light, and can still discriminate well the difference in light intensity even under dim light, exhibiting a well dim-light vision ability. The results provide a basis for new physical trapping techniques based on visual behavior regulation.

Key words: Grapholita molesta, oviposition preference, light, sunny sides, shaded sides, dim-light vision