Hogs and hazelnuts: adaptively managing pest spillover in the agricultural-wildland matrix

Abstract

Pest spillover from wildlands to farms can create conflict between habitat conservation and agricultural production. For example, the key economic pest of hazelnuts in Oregon’s Willamette Valley is the filbertworm (Cydia latiferreana), a moth hosted by the native Oregon white oak (Quercus garryana). Oak habitat near hazelnut orchards can sustain source populations that compound pest load in hazelnuts throughout the growing season. This dynamic is of conservational concern as historical oak habitat has been greatly reduced and what remains is almost entirely on private land, often in proximity to hazelnut orchards. Here, we present a novel strategy to reconcile this regional conflict by using hogs (Sus domesticus) to reduce pest populations through prescribed foraging. From 2018 to 2020 we prescribed hog-foraging in early fall to glean filbertworm-infested acorns from an oak woodland understory. Hogs were both highly successful at reducing the total number of infested acorns and the ratio of infested acorns the following year. Despite an oak-masting year in 2019, foraging reduced both the emerging and adult mating population of filbertworm the following year. We did not measure significant changes in the woodland understory, suggesting intermittent hog-foraging may not entail tradeoffs for understory vegetation. Our results demonstrate that prescribed foraging in oak patches can be an effective strategy to reduce filbertworm source populations. By benefiting both conservation and farmers, this adaptive pest management approach provides a model for similar challenges and conflicts across the agricultural-wildland matrix.