Tipula larval populations affected by soil edaphic and microbiological properties: Insights from Ireland and Scotland

Herbivorous soil-dwelling pests cause damage in agriculture through decreases in root and shoot biomass, which can affect both plant and economic yield. Having a greater understanding of the soil environment of these pests could identify potential avenues for mitigation/control strategies. Leatherjackets (Tipula larvae) are pests of grasslands and cereals across Europe and North America, for which there are no known effective or economical non-chemical control options. Within this study, the soil habitats of Tipula paludosa in grassland and cereal sites were examined across Ireland and Scotland, to assess the impact of edaphic properties on their occurrence. Significant correlations were observed between leatherjacket populations and silt content, positively in cereal sites and negatively in grasslands. Larval populations were positively correlated with Na, Al, and Zn, and negatively correlated with Fe, Mn, and K. As grasslands were more vulnerable to high T. paludosa infestations, their soil microbiomes were also examined from a prokaryotic and fungal community structure context. Microbial community structure was linked to leatherjacket occurrence and abundance, and specific microbial genera were associated with the absence or high prevalence of larvae. Plant growth promoting bacteria (Flavobacterium) and fungi (Mortierellaceae) were significantly more abundant in soils where larvae were absent. Where there were larval populations above the economic threshold for crop damage, significantly higher abundances of anaerobic bacteria (Anaerolineaceae) were present. Studies of pest related soil microbiomes and environments could hold promise for future pest suppression strategies via management and biocontrol opportunities.

植食性土栖害虫（herbivorous soil-dwelling pests）会通过降低作物根系与地上部生物量，对农业生产造成损害，进而影响作物产量与经济效益。深入了解这类害虫的土壤栖息环境，或可发掘出害虫防控与治理策略的潜在可行路径。大蚊幼虫（leatherjackets，Tipula larvae）是欧洲与北美地区草地及谷类作物的主要害虫，目前尚无有效且经济的非化学防控手段。本研究对爱尔兰与苏格兰境内草地及谷类作物田中的华丽大蚊（Tipula paludosa）土壤栖息生境展开调查，以评估土壤理化性质（edaphic properties）对其种群发生的影响。研究发现，大蚊幼虫种群与土壤粉粒含量存在显著相关性：在谷类作物田中呈正相关，而在草地生境中则呈负相关。幼虫种群与土壤中的钠（Na）、铝（Al）及锌（Zn）含量呈正相关，与铁（Fe）、锰（Mn）及钾（K）含量呈负相关。鉴于草地更易遭受华丽大蚊的重度侵染，本研究同时从原核生物与真菌群落结构的维度，对其土壤微生物组（soil microbiomes）展开分析。微生物群落结构与大蚊幼虫的发生情况及种群丰度存在关联，且特定微生物属类群与幼虫的缺失或高侵染率显著相关。在无幼虫栖息的土壤中，植物促生细菌（plant growth promoting bacteria）的黄杆菌属（Flavobacterium）与真菌的被孢霉科（Mortierellaceae）丰度显著更高。当幼虫种群达到造成作物经济损失的阈值时，厌氧细菌中的厌氧绳菌科（Anaerolineaceae）丰度显著升高。针对害虫相关土壤微生物组与栖息环境的研究，或可为未来通过土壤管理与生物防控手段实现害虫种群抑制提供新的可行方向。