Ground cover and floral resources in shelterbelts increase the abundance of beneficial hymenopteran families

摘要

Hymenopteran parasitoids are important natural enemies of pest species in many agricultural crops, including grapes, and there is increasing interest in using habitat manipulation to enhance populations. In the present study, we investigated which vegetation variables of shelterbelts are associated with increased hymenopteran family abundance by screening 60 shelterbelts adjacent to vineyards or pasture near Melbourne, Australia. Associations between vegetation characteristics and parasitoid abundance, sampled five times at monthly intervals using canopy sticky traps, were investigated. The presence of vineyard or pasture adjacent to the shelterbelt had no impact on hymenopteran family abundance within the shelterbelt. The availability of floral resources influenced a single family; the abundance of the Trichogrammatidae was doubled by the presence of canopy floral resources. By contrast, an increased abundance of some large Hymenoptera families was associated with a decreasing leaf litter depth and the proportion of introduced ground cover, an increased grass height and the amount of ground with vegetated cover. These findings suggest that specific manipulations of shelterbelts could increase populations of beneficials to some degree, with potential effects on pests.