The fall armyworm (Spodoptera frugiperda) is a well-known pest that causes significant economic losses worldwide. Light is a crucial external factor affecting the growth and development of insects. LED lights are commonly used in manufacturing and daily life because they are environmentally friendly and emit light across multiple wavelengths. However, few studies have examined the effects of different wavelength lights on the growth and reproduction of S. frugiperda, and even fewer have explored the underlying mechanisms. To find new strategies for integrated pest management amid the growing challenge of pesticide resistance, this study investigated the effects of 520 nm (green) and 570 nm (yellow) LED light on the growth, development, and reproductive capacity of S. frugiperda. Since vitellogenin receptor (VgR) is a key reproductive protein in insects, the full-length SfVgR gene was cloned, its spatial and temporal expression was analyzed, and RNAi-mediated knockdown was performed to explore the mechanisms under different light treatments. The results showed that exposure to either 520 nm (green) or 570 nm (yellow) LED light reduced developmental periods, increased sex ratios, and reduced pupation and emergence rates of S. frugiperda. Additionally, 520 nm (green) light notably suppressed the expression of both SfVg and SfVgR mRNA, which impeded ovarian development and significantly decreased fecundity. Moreover, silencing SfVgR led to abnormal oocyte development and markedly lowered fertility. These findings suggest that using 520 nm (green) light at night or RNAi targeting SfVgR could serve as novel approaches for the integrated management of S. frugiperda.
