Influence of Japanese beetle Popillia japonica Newman (Coleoptera: Scarabaeidae) on greenhouse gas emissions from infested soil

Root-feeding scarab larvae have the potential to accelerate root inputs to soil and stimulate the decomposition of existing soil organic matter. Aside from their negative impacts on the sustainability of managed ecosystems, scarab larvae are estimated to contribute 0.2-1.8% of soil N₂O emissions. Surprisingly, the impact of the highly invasive Japanese beetle Popillia japonica Newman (JB), on greenhouse gas (GHG) emissions from infested soil has not been examined. We assessed the impact of JB on soil GHG emissions, both in manipulative laboratory experiments and in the field. In laboratory microcosms, GHG emission rates were determined from JB larvae, JB infested soil, and post-infested soil. Emission of CO₂, CH₄, and N₂O per grub from infested soil were 6.3, 5.9 and 18.6 times higher, respectively, than emission from JB larvae alone. The emission per grub of CO₂ from post-infested soils (107.9±27.4 mg CO₂/Kg soil.h.grub) was 1.3X higher than that from JB larvae alone while the CH₄ or N₂O larval footprint in post-infested soils were not significant. At field sites, JB larval density was a significant predictor of soil CO₂ and CH₄ emissions, with 28.8±12.2 mg CO₂/m².h.grub, and 1.9±0.5 µg CH₄/m².h.grub. These results reveal that JB larvae promote GHG emissions from the soil directly through respiration and metabolic activities, and indirectly, by potentially changing physical, chemical, and biological conditions in soils favoring microbial processes involved in GHG emissions.