Diversification of agricultural landscapes is a cornerstone of conservation biological control. Provision of critical habitat and food resources for natural enemies of crop pests by perennial vegetation may be particularly important in frequently disturbed, annual cropping systems. For intensive annual vegetable production systems we determined if perennial vegetation enhanced natural enemy abundance or diversity at two scales: the field-level (vacuum samples on hedgerows adjacent to vegetable crops) and the landscape-level (Malaise trap samples in vegetable fields embedded in a range of vegetation and land cover mosaics). Further, natural enemy and pest movement rates from hedgerows into adjacent fields were tracked with fluorescent pigment, and parasitism rates of sentinel moth larvae (Trichoplusia ni) measured to determine if diversity, abundance, or movement rates of natural enemies predict conservation biological control potential.
Results/Conclusions

Results include: (1) a positive association between the amount of perennial vegetation cover and ichneumonid wasp species diversity, and a negative association between annual cropland cover and species diversity of ichneumonid wasps, (2) a positive association between parasitoid abundance and presence of Baccharis pilularis shrubs in hedgerows versus a negative association between these factors on the landscape-scale, (3) differential usage of hedgerow shrub species throughout the season, (4) differential movement rates of pests and natural enemies from hedgerows into the crop field, and (5) a tenuous association between biodiversity and parasitism rates. Effects of the spatial scale of analysis employed and methodological challenges for demonstrating conservation biological control will be discussed.