Reducing ploughing promotes ground-nesting flying insects

Many flying insects, such as bees, wasps, and hoverflies, live aboveground, but depend on soil for nesting, development, and overwintering. In agricultural landscapes, soil is managed for production and therefore frequently subjected to disturbances such as ploughing, potentially influencing flying insects during their belowground life stages. To investigate the effects of ploughing on ground-nesting flying insects, we conducted a two-year field experiment in twelve wildflower strips. All strips were ploughed and sown during establishment and were 0, 1, 2 or 3 years old at the start of the experiment. Within wildflower strips, we compared unploughed control plots with adjacent treatment plots that were ploughed between the two sampling years. This design allowed us to assess the ploughing effect across different ages and whether time since establishment influenced insects. We used emergence traps to sample insects emerging from the soil and measured insect biomass, abundance, and body size. We found that ploughing substantially reduced ground-nesting flying insect biomass. When wildflower strips were left unploughed, biomass increased rapidly, particularly during the first years after their establishment. Ploughing consistently reduced insect biomass to equally low levels regardless of how long the wildflower strips had been established. This was driven primarily by declines in the abundance of large insects. Our findings highlight that even moderate reductions in ploughing frequency - for example, only every second year - can benefit ground-nesting flying insects and point to the potential for incorporating reduced ploughing frequencies into agricultural management and agri-environmental schemes. • Ploughing reduced the biomass of ground-nesting insects in wildflower strips. • Biomass rose rapidly in unploughed sites, especially during the first years. • Biomass dropped to equally low levels after ploughing, regardless of recovery time. • Large insects were most affected by ploughing, causing biomass drops. • Reducing ploughing, even to every two years, enhances insect biomass.