2018 ASHS Annual Conference

Herbaceous flowering or woody plant borders adjacent to highbush blueberry (Vaccinium corymbosum) fields have the potential to benefit both native pollinators and predatory insects and birds that feed on key blueberry pests, such as spotted wing drosophila (Drosophila suzukii; SWD). However, they may also draw pollinators away from the crop, serve as overwintering and/or refugia sites for SWD, and increase populations of wild birds that feed on fruit and transmit foodborne pathogens. The objective of this project was to explore the impacts of border vegetation adjacent to blueberry fields on multifunctional biodiversity. In 2017 we measured pollination services, populations of beneficial and pest insect and bird species, and production attributes of blueberry grown with or without adjacent border vegetation on 9 commercial farms in northwest Washington. Our border vegetation treatments include: 1) Control (primarily medium-height grasses); 2) Woody perennial vegetation [mixture of woody species including Cedar (Cedrus sp.) and Arborvitae (Thuja sp.)]; and; 3) Herbaceous vegetation [mixture of monocots (e.g., Poa sp. and quackgrass (Elymus sp) and broadleaves (e.g., Taraxacum officinale)]. There were no differences in pollinator abundance, pollinator visitation rates, estimated yield, and fruit quality across the treatments. Pest and beneficial insects were collected during a 16-week period using an insect vacuum and apple cider vinegar traps. All treatments exhibited similar pest:beneficial ratios, but arthropod numbers varied widely between treatments. Herbaceous borders represented nearly 50% of the total arthropods collected, while the control exhibited over twice that of perennial borders. Spotted wing drosophila were absent in all localities. Sticky card data used to monitor arthropod movement between blueberry fields and their borders suggested there were no differences in field populations by treatment. However, there were overall greater populations of both pest and beneficial insects in the border vegetation relative to in the blueberry field. Point count surveys conducted in hedges and blueberry fields were used to evaluate the effects of border vegetation on wild bird populations. Pest species were observed in all habitats, but treatment trends suggest greater density of some species in some habitats. Preliminary data from this project show that while arthropod numbers vary among different borders, blueberry fields remain low in insect biodiversity, which is likely influenced by weekly SWD insecticide applications. Our evaluated border treatments have small to negligible impacts on our measured variables and no clear multifunctional benefits associated with our different border vegetation treatments were detected.