Does pasture plant diversity influence abundance and diversity of lacewings and Hymenopteran parasitoids?

The lack of plant biodiversity in New Zealand pastoral ecosystems may limit the abundance and diversity of generalist parasitoids and predators, predisposing these ecosystems to pest outbreaks. To test this hypothesis, patches of four treatments of increasing plant complexity were established in pasture, commencing with ryegrass alone, and increasing exponentially up to eight forage plants. In summer 2017, suction samples were taken to assess how plant diversity influenced the abundance and diversity of lacewings and parasitic Hymenoptera aggregating in the patches. While plant diversity had no impact on lacewing abundance, fewer parasitic Hymenoptera were recovered from the ryegrass only plots compared to more diverse plots and more parasitoid families were represented in the more diverse plant treatments compared to the less diverse treatments. Such diversity may have beneficial impacts on pasture ecosystem stability and pest outbreak risk