Wildflower plantings adjacent to commercial highbush blueberry fields do not increase natural enemy populations or reduce Drosophila suzukii (Diptera: Drosophilidae) populations.

Abstract

Intensive agricultural production can reduce beneficial insects by limiting access to undisturbed habitat. Wildflower plantings are promoted as conservation strategies to support pollinators and natural enemies on farms, yet their effects on certain crop pests remain understudied. We evaluated whether wildflower plantings adjacent to highbush blueberry (Vaccinium corymbosum L.) fields increased natural enemy abundances and reduced Drosophila suzukii populations compared to fields without this practice. In 2019 and 2020, across 12 farms in Michigan representing 3 management types (conventional management without wildflower plantings, conventional with wildflower plantings, or no chemical pest management), we quantified natural enemies, monitored adult D. suzukii abundance and fruit infestation, and measured removal of D. suzukii pupae. Unsprayed fields supported the highest natural enemy abundance and pupal removal but also had the highest D. suzukii abundance. There was some limited evidence for wildflower plantings increasing natural enemies, such as post-harvest, but overall, there was no significant difference between conventionally managed sites with and without wildflower plantings, and no impact on D. suzukii pupal removal. Additionally, wildflower plantings increased D. suzukii adult abundances post-harvest and in the wildflower plantings compared to mown field margins. Fruit infestation generally remained low in conventionally managed fields irrespective of wildflower plantings. Together, these results suggest that wildflower plantings only provide limited benefits for natural enemies and do not aid in D. suzukii control. Though typically established for pollinators, understanding how habitat enhancements impact particular pests of concern is essential for designing strategies tailored to specific production systems.