Light intensity differentially mediates the life cycle of lepidopteran leaf feeders and stem borers.

BACKGROUND: Leaf feeders, such as Spodoptera frugiperda and Spodoptera litura, and stem borers Ostrinia furnacalis and Chilo suppressalis, occupy two different niches and are well adapted to their particular environments. Borer larvae burrow and inhabit the interior of stems, which are relatively dark. By contrast, the larvae of leaf feeders are exposed to sunlight during feeding. We therefore designed series of experiments to evaluate the effect of light intensity (0, 2000, and 10 000 lx) on these pests with different feeding modes. RESULTS: The development of all four pests was significantly delayed at 0 lx. Importantly, light intensity affected the development of both male and female larvae of borers, but only significantly affected male larvae of leaf feeders. Furthermore, the proportion of female offspring of leaf feeders increased with increasing light intensity (S. frugiperda: 33.89%, 42.26%, 57.41%; S. litura: 38.90%, 51.75%, 65.08%), but no significant differences were found in stem borers. This research also revealed that the survival rate of female leaf feeders did not vary across light intensities, but that of males decreased with increasing light intensity (S. frugiperda: 97.78%, 85.86%, 61.21%; S. litura: 95.83%, 73.54%, 58.99%). CONCLUSION: These results improve our understanding of how light intensity affects sex differences in important lepidopteran pests occupying different feeding niches and their ecological interactions with abiotic factors in agroecosystems. © 2024 Society of Chemical Industry.

Investigation of the effects of biochar amendment on soil under freeze‒thaw cycles and the underlying mechanism.

Biochar (BC) is widely utilized as a soil amendment; however, for widely distributed seasonally frozen soils, the effect of BC on soil and the optimal utilization of BC during the freeze‒thaw process are still unclear. In this study, the effects of freeze‒thaw aged biochar (FT-BC) and BC on soil properties and wheat cultivation were systematically investigated, and the underlying interaction mechanism between BC and soil was explored. The results show that FT-BC dramatically reduces the adverse effects of freeze‒thaw cycles on soil, enhances wheat growth, and increases dry matter yield by 17.5 %, which is mainly attributed to the ability of FT-BC to maintain soil structure, reduce water loss rates to below 0.20 g/h, and decrease nitrogen leaching by more than 20 % during freeze‒thaw cycles. Additionally, fresh BC had a greater effect on the fixation of cadmium than FT-BC in the soil, reducing its accumulation in wheat by 22.5 %. Multiple characterizations revealed that the freeze‒thaw process increased the porosity and specific surface area of FT-BC, providing more sites for water and nitrogen adsorption, whereas the dissolved organic matter released from fresh BC had a better ability to trap cadmium. These findings provide insights into the interactions between BC and soil components during the freeze‒thaw process and suggest the optimized utilization of fresh BC and FT-BC for different soil repair purposes.