Increasing the pest control services provided by flowering plants in agroecosystems

Pest control is a key ecosystem service that is diminished in many agricultural systems. Insect predator and parasitoid populations may be augmented when they have access to nectar and pollen. Therefore, a need for integrating flowering resource plants into agricultural landscapes is well recognized. The most frequently used plant species are annuals exotic to the area of study. Perennial native plants, however, vary from region to region and often have no published record of attractiveness to predators and parasitoids. We tested the hypotheses that 1) predator and parasitoid abundance at perennial native plant species was equal or greater than at annual exotics and 2) plant characteristics play a role in explaining differences in insect abundance at flowering plants. We compared natural enemy abundance at 43 perennial native Michigan plant species and five exotic annuals during summer 2005. Natural enemy abundance at many perennial natives was equal or greater than at previously recommended exotic annuals. We also measured plant characteristics of all 48 plant species to determine which best explain variability in natural enemy abundance at each plant species. These included: week of peak bloom, maximum flower height, floral area, flower color, and corolla depth and width. Natural enemy abundance increased significantly with peak bloom week and floral area. This suggests that within any given bloom period, selecting plants with the largest floral area would simplify screening for highly attractive plants and could increase the pest management service of agroecosystems.