Assessing the effects of non-honeybee insects on pollination in diversified organic farms

View the project final report

• 2016 annual report

Commodities

Practices

• Crop Production: beekeeping, intercropping, pollination, pollinator habitat, pollinator health
• Education and Training: demonstration, farmer to farmer, on-farm/ranch research, participatory research, workshop
• Natural Resources/Environment: biodiversity
• Production Systems: organic agriculture, transitioning to organic

The goal of our project was to characterize communities of non-bee pollinating insects on organic farms and urban gardens in the Puget Sound region of western Washington State, and examine their interactions with bees. To achieve this, we measured the abundance and diversity of flowering plants on 35 farms in 2015 and 2016, and monitored insect visitation to these plants. While these plants were visited primarily by bees, we also observed frequent visits from one key group of non-bee insects, syrphid flies (Diptera: Syrphidae). Other groups of non-bee pollinating insects, including moths and butterflies (, were rare. Syrphid flies visited the reproductive structures of 83% of the different flowering plant species in our farms, suggesting they may be important pollinators. Moreover, syrphid flies visited 3 of the 4 flowering plant species that were not visited by bees, suggesting that these two groups have complementarity in terms of pollination services. Syrphid abundance was similar on farms location in urban compared to rural locations, but increased with greater floral diversity on farms in either type of landscape.

Our research goals were paired with an extensive outreach and education program, whereby we disseminated information to hundreds of growers, educators, and researchers of the importance of these non-bee pollinating insects through a wide array of forums. This outreach has resulted in the development of a pollinator monitoring team of growers and citizen scientists contributing to an extensive observational study aimed at pollinator conservation in the western Washington region. Using the data collected during this project, to date we have published a peer-reviewed guide to native pollinators of western Washington, including non-bee pollinators. We are in the process of developing a scientific publication as well on non-bee pollinating insects that will be submitted in the fall or early spring 2018.

Introduction

Insect pollinators are essential for the production of 70% of the most widely consumed global food crops (Klein et al., 2007). Historically, it has been assumed that honeybees and native bees provide the majority of these pollination services (Garibaldi et al., 2013). Many non-bee insects such as moths, butterflies, flies, wasps, and beetles also function as pollinators, however (Garibaldi et al., 2013; Rader et al., 2009). In addition, non-bee insects might indirectly impact pollination by interacting with bees (Romero, Antiqueira, & Koricheva, 2011). However, the ecological impact of non-bee insects, and whether they contribute to sustainable crop pollination on farms, has rarely been studied. Research on the impacts of non-bee insects on pollination services is thus critical, especially considering the recent, widespread declines in honeybee and native bee populations (Listabarth, 2001; Rader, Howlett, Cunningham, Westcott, & Edwards, 2012). If non-bee insects provide substantial pollination services, or increase the pollination efficiency of bees, then conserving these species could improve the stability and profitability of many agricultural systems (Crowder, Northfield, Strand, & Snyder, 2010).

Project Objectives

1. Our project objectives were as follows
   1. Characterize communities of non-bee insects on diversified organic farms and their direct contribution to crop pollination
   2. Examine whether non-bee insects indirectly affect crop pollination by bees
   3. Educate farmers and the public on the role of non-bee pollinators in sustainable farming