University of Oregon - Hallett Lab
Our pigs spent autumn under the canopy of oaks and hazelnuts in constant pursuit of falling nuts. We did this to explore the potential for pigs to interrupt the life cycle of our hazelnut’s most feared (and effective) pest—Filbert Worm. These worms are native to Oregon and hatch as moths in early summer to lay their eggs near nuts before their hard shell has time to develop.
The worm burrows into the nut and eats the kernel all summer long before falling to the ground in October.
Our pigs spent autumn under the canopy of oaks and hazelnuts in constant pursuit of falling nuts. We did this to explore the potential for pigs to interrupt the life cycle of our hazelnut’s most feared (and effective) pest—Filbert Worm. These worms are native to Oregon and hatch as moths in early summer to lay their eggs near nuts before their hard shell has time to develop. The worm burrows into the nut and eats the kernel all summer long before falling to the ground in October. Assuming the worm isn’t removed from the ground, it will transform into a moth the following year and repeat the process. Filbert worms are a major problem in most Oregon orchards, and they are usually combated with pesticide. If a farmer’s orchard neighbors a stand of oaks, they are often advised to remove the native host of filbert worm: acorns.
In partnering with the University of Oregon, we spent 2018 moving our pigs through different oak and hazelnut paddocks, making sure to leave control areas untouched. We found that pigs no doubt have a strong preference for both hazelnuts and acorns. We’re won’t know the full results of the project until filbert worm moths are caught in 2019, but we sure don’t see a lot of nuts laying on the ground.
Project summary:
"The spillover of pests from wildlands to farmland creates conflict between habitat conservation and agricultural production. This is the case in the Pacific Northwest; where Oregon white oaks harbor the filbertworm moth, the key economic pest for hazelnuts. These oaks are dispersed throughout a matrix of private agricultural land and comprise one of the most imperiled habitats in Oregon – with less than 5% remaining in the state. Furthermore, the Willamette Valley accounts for almost all the hazelnuts grown nationwide and pest pressure incentivizes landowners to clear oaks from their property to reduce crop damage and pesticide cost.
A growing number of landowners are recognizing the need to conserve oak habitat and are looking for ways to adaptively manage filbertworm within the landscape. Agroforestry practices such as silvopastures, where animals graze within forested areas, is a promising tool for disrupting the life cycle of agricultural pests and can help align conservation principles with economic goals. Likewise, domestic hogs have historically grazed oak habitat in Spain and Portugal, creating some of the most desired ham in the world. If prescribed hog-grazing of oak habitat in the Willamette Valley is carefully managed, it could have significant economic and ecological potential for diversifying farms. With this in mind, we set out to see if prescribed hog-grazing reduces filbertworm pest pressure over the course of two years. Between 2018 and 2020, hogs grazed oak woodlands at My Brother’s Farm in October, when acorns infested with the filbertworm larvae fall to the ground. To minimize the effects of grazing on the understory vegetation and soil, the hogs were rotated through 2-acre paddocks every 4-5 days. To measure the population of filbertworm throughout Spring and Summer, we used ground emergence traps and commercial sticky traps in the oak canopy.
We found that hogs were extremely effective at removing infested acorns while having an insignificant change in understory vegetation. Additionally, the emerging filbertworm populations in the grazed paddocks diverged from the control with near-zero emerging in 2020. These results, along with an increased demand for nature-friendly pork and a decreased spillover potential, are a promising step towards resolving the conflict between oak conservation and hazelnut production in the Pacific Northwest. Although hog-grazing may not be practical in some cases, prescribed burns, and alternative grazers such as goats, could be additional tools for adaptively managing filbertworm and other pests in the agricultural-wildland matrix."
