Spider foraging strategies dominate pest suppression in organic tea plantations

Organic management of crops generally leads to greater predator richness. However conservation of natural enemy species richness does not consistently strengthen herbivore suppression. Here we explored relationships between abundance and diversity of predatory spiders with two distinct foraging strategies and their prey, leafhopper pests. In three organic tea plantations, we investigated abundance of these spiders, and population dynamics of an important tea green leafhopper pest, Empoasca vitis (Homoptera: Cicadellidae). We found that abundance and diversity of actively hunting spiders were significantly negatively correlated with leafhopper pest populations, but sit-and-wait spiders were not. The latter may have been limited by intraguild predation or other trophic interactions. Furthermore, there was no significant correlation between total spider and leafhopper numbers. Our study thus suggests that predator foraging strategy might be a key functional trait that can help to explain variation in pest suppression in agricultural systems.