Conservation biological control seeks to suppress insect pests by encouraging resident natural enemy populations. The use of non-crop ‘refuge’ areas is one such approach: the refuge is meant to provide food and shelter for predators when farm fields are unfavorable (e.g. winter) and then to supply those predators to crop fields during the growing season. While a handful of refuge strategies have been developed (e.g. beetle banks in grains), the elements of a successful refuge remain obscure for many crops and predators, including spiders. We conducted a pilot study to describe the spider fauna in refuge and crop habitats on a small, diverse vegetable farm in Virginia. We framed our study around two questions: 1) Does spider abundance or composition vary among farm habitats? and 2) Do refuge areas support agriculturally-relevant spiders? Using suction sampling in early fall, we collected spiders in an intentional refuge, a one-year-old fallow field (potential refuge), and three annual crop plantings (early tomatoes, late tomatoes, and peppers).
Results/Conclusions
Spider abundance was high (>50 spiders/m2) in both the crop and refuge areas, with highest densities in the intentional refuge and the early tomato planting. While all habitats hosted a handful of common spiders, refuge areas contained more hunting spiders while crop fields were dominated by small web-builders (≤ 2 mm). Notably, several species of known agricultural importance, such as the lynx spider Oxyopes salticus, were most numerous in non-crop habitats. Our results are consistent with a role for refuges in supplying spiders to farm fields; however, future studies are needed to quantify spider movement between habitats in the farm landscape.
