Oviposition site selection in the crepuscular moth, Grapholita molesta: does light matter?

Abstract

Some insects that particularly prefer sunny or shaded sites use light intensity to locate suitable oviposition sites during the day. However, it is not known whether crepuscular species can be guided by light for oviposition under dim or variable light conditions. We used the crepuscular moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a major pest of stone and pome fruits worldwide, to investigate oviposition response to light at various intensities (1000, 100, 10, and 1 mW m −2 ). Light intensity in sunny sites in a peach tree canopy is about 10× higher than in shaded sites. In both light vs. dark and brighter light vs. darker light choices, G. molesta females can discriminate differences in light intensity, exhibiting a strong preference for brighter light, independent of light intensity. Moreover, the light-dependent oviposition responses did not change when exposed to odor stimuli. Our findings show that this crepuscular moth G. molesta can use light intensity to direct oviposition toward relatively sunny sites under dim light conditions. This study highlights the importance of vision for crepuscular species in oviposition site selection.

Spectral sensitivity of retinal photoreceptors of tortricid moths is not tuned to diel activity period

“…Tortricids show preference when given a choice of traps of different colours (Knight and Miliczky, 2003;Myers et al, 2009;Zhao et al, 2013;Rayegan et al, 2016). In addition, mated females of G. molesta show colour and light intensity oviposition preferences under laboratory conditions (Yang et al, 2020(Yang et al, , 2022. Tortricid moths are an economically important group for which the alternative to insecticide control is mostly based on odour-baited traps and mating disruption with sex pheromones (Knight et al, 2019).…”

“…However, they use vision to fly and to navigate in odour plumes (Navarro-Roldán et al, 2019), and probably to recognize and land on the host plants. Vision could also be involved in mating and oviposition behaviour (Yang et al, 2020(Yang et al, , 2022. Colour has some effect on the capture of males in pheromone traps (Knight and Miliczky, 2003;Knight and Fisher, 2006;Zhao et al, 2013;Padilha et al, 2018;Rayegan et al, 2016), and UV light appears to influence male but not female captures in semiochemical traps (Adasme, 2022).…”

Fine structure of the compound eyes of the crepuscular moth Grapholita molesta (Busck 1916) (Lepidoptera: Tortricidae)

“…It has however been observed that adult Grapholita molesta are attracted to light, preferring violet and green light ( Sun et al, 2014 ). Our recent works show that G. molesta can visually discriminate between plants in microhabitats to guide oviposition even in dim light, exhibiting a preference for higher brightness/intensity ( Yang et al, 2020 ; 2022 ). Electroretinogram (ERG) spectral sensitivity measurements additionally reveal that three photoreceptor classes are present in compound eyes of G. molesta , with sensitivities peaking at UV (355 nm), blue (440 nm) and green (525 nm) wavelengths ( Martín-Gabarrella et al, 2023 ).…”