Enhancement of pollination by native bees in blueberries and cranberries

View the project final report

• 2009 annual report
• 2010 annual report

Commodities

• Fruits: berries (brambles), berries (cranberries)

Practices

• Education and Training: extension, on-farm/ranch research
• Production Systems: general crop production

Pollination is critical for blueberry and cranberry production in the Pacific Northwest. Growers typically rent one-four honey bee hives per acre, but diseases and the recent colony collapse disorder have reduced their availability and made rentals more expensive. In addition, honey bees do not perform well on cold and windy days. Native bees, especially bumble bees, are adapted to Oregon’s climate and are better pollinators of blueberries and cranberries, but they are not consistent or predictable and are inadequate for the large numbers of flowers in berry fields. Commercial bumble bees can be purchased in most U.S. states, but this is prohibited in Oregon. To provide Oregon growers a competitive edge there is an urgent need to enhance populations of native bees for improving pollination and thereby increasing yield and grower profit. The research is aligned to Western SARE goals as it seeks to: 1) Enhance pollination for increasing PNW farmers' profits and competitiveness; 2) Augment farmers' income by reducing honey bee rental costs; 3) Reduce insecticide applications and optimize timing of sprays; 4) Promote crop diversification through addition of hedgerows of flowering plants; 5) Examine practices for enhancing native bee pollinators for sustainable and economic crop production. Objectives and Methodology: 1) Estimate native bee pollinator species diversity and abundance in berry fields. A native bee census will be conducted through weekly monitoring during bloom, and captured bees will be preserved and identified. 2) Compare honey bee and bumble bee foraging behaviors in berry fields. Weekly two-minute visual counts will be made of adults at different times of the day during bloom to compare the activity of each species. Ten bumble bees and 10 honey bees will be collected from flowers every hour once a week, and the numbers with pollen and pollen weight and identity will be compared. 3) Evaluate the impacts of insecticide sprays on bumble bees. In a caged study, bumble bees will be exposed to flowers from fields treated with insecticides, and mortality will be determined. 4) Examine strategies for drawing native bees to berry fields. A cluster of attractive blue devices will be placed in fields (strategy 1) and bee attractive flowering plants will be planted in adjacent areas (strategy 2) to determine if these two tactics draw additional bees to the fields. 5) Build capacity in growers to identify, protect and enhance native bee pollinators in their fields for increasing berry production. Native bee identification workshops will be organized, and growers will be trained in strategies for preserving and enhancing native bees in berry-growing regions. Experimental design: Each test will include at least three blueberry fields and three cranberry beds, each one serving as a replication. Paired t-tests and ANOVA will be used for statistical analysis. Producer Involvement will be extensive as the program will adopt the Type D model. Growers have participated in proposal development and will be actively engaged in experiments to be conducted primarily in their fields. The evaluation plan includes review of feedback on evaluation surveys administered during meetings, comparison of 'before' and 'after' scores on annual grower surveys and record of hits to the webpage. Measurable impacts include estimation of growers who can identify bumble bees and those that adopt new practices for enhancing native bees in their fields. Expected short-term outcome: Growers will have increased knowledge about the efficiencies of honey bees and bumble bees in pollination of berry crops, the ability to recognize native bumble bees and the ability to estimate their abundances. Expected medium-term outcome: Growers will time pesticide sprays to minimize negative impacts on native bees, change attitudes about flowering plants in the area and adopt practices that will draw native bees to their fields. Over time there will be an increase in flowering plants that attract bees in landscapes around berry fields. Educational products include presentations at meetings, pictorial native bee identification key and extension and peer-reviewed articles.

Our long-term goal is to enhance native bee populations in berry fields for augmenting pollination and thereby increasing yield and income for berry producers. In this project, two separate programs are being integrated into one with similar experiments being conducted in blueberry fields in the Willamette Valley and cranberry filds on the coast. Our objectives are to:

1) Estimate native bee pollinator species diversity and abundance in berry fields.

2) Compare honey bee and bumble bee foraging behaviors in berry fields.

3) Evaluate the impacts of insecticide sprays on native bees.

4) Examine strategies for enhancing native bees in berry fields.

5) Build capacity in growers to identify, protect and enhance native bee pollinators in their fields for increasing berry production.