Maximizing Pollinator Services from Native Bees

Maximizing Pollinator Services from Native Bees

Summary

In this field season we visited the four farm sites (we have added one because of the original’s lack of pollinators). We placed traps, collected the captured insects, prepared and mounted the specimens. We have focused identification on bees in the genera Bombus and Andrena as they appear to be those bees most involved in pollination of blueberries. We catch other genera in the traps set in the blueberry fields but we do not see them working the flowers. 

We have identified approximately 20 different Andrena species collected in the traps. We also sampled the field with a vacuum capture apparatus. If we discovered a bee on a blueberry flower we sucked it off the flower. In all three locations and four separate samplings (We sampled one location twice), we consistently found only two species of Andrena on blueberry flowers, Andrena carlini, and A. vicina.  The only thing different about locations was the ratio of the two species. 

Rather than trap Bombus species we proceeded with visual sampling. We found some 6 species of Bombus in the field locations although they were not present in equal numbers. More detail in following report. 

We have documented nesting habits of both genera although these species still present challenges for the way they are able to disguise their nest entrances. We have photographic documentation of same. 

We have a preliminary list of plants to provide forage for the genus Andrena whose life cycle extends several weeks on either side of the blueberry flowering window. Because Bombus is present for the whole growing season and builds significant numbers through their annual hive system, a completely different strategy regarding forage is discussed. 

This summer we will continue searching for nests and documenting observations regarding nesting. We will also produce two videos this summer. The first two years focused on determining the primary pollinating species, and having determined this, we can proceed with video production. 

Lastly, the results of this grant study have been presented to three professional audiences. The first is the Upper Midwest Fruit and Vegetable Growers’ Conference and the second is the Third Crop Producers Meetings sponsored by Rural Advantage. A presentation was also made to academic professionals as part of the Great Lakes Vegetable Working Group on 2/28/2017.

In addition results have been included in a series of presentations to non-professional audiences such as master gardeners and attendees at spring horticultural events. To date 6 such presentations have been made and two are scheduled for March and May of this year 2017.

Objectives/Performance Targets

1. Identify the best candidate native bee species to provide pollination services to the fruit and vegetable growers in the region

2. Determine critical parameters of nesting habitat for these identified species

3. Develop recommendations for native bee nesting habitat for fruit & vegetable growers

4. Develop a suggested plant list specific to each crop which will provide forage outside the flowering window of the crop and meet the needs of the identified pollinators

5. Develop a video demonstrating nesting habitat recommendations
To be developed and submitted on September 30, 2017

6. Develop a video demonstrating forage recommendations
To be developed and submitted on September 30, 2017

7. Present findings to various audiences

Accomplishments/Milestones

1. Identify the best candidate native bee species to provide pollination services to the fruit and vegetable growers in the region
4 bumble bee species and two Andrena species were observed to be the native bee species most active in the observed blueberry fields.
A total of 19 different Andrena species have been identified from bees captured in field years 2015 and 2016 (Table 1). Bees were captured while visiting blueberry flowers over a 50 minute time period. Only two species were captured in flowers during sampling (Andrena carlini and Andrena vicina, Table 2). 6 bumble bee species were observed during transect observations of the blueberry fields (Table 3). The most commonly encountered species in rank order was as follows: B. impatiens, B. griseocollis, B. ternarius, B. auricomus, B. bimaculatus, and B. vagans (Table 3).

The density of bumble bees was determined by counts over time (Table 4). Significant variation was encountered among differing field locations. The following paragraphs will appear in the discussion section of the final report. They are presented he to provide a context for which to consider the reported data.

To provide context for the density numbers please consider the following:
Rao and Stephen (2010) reported seeing 1.0 bee per minute in their survey of bumble bees in blueberry fields in the Willamette Valley of Oregon. It should be noted that 10% of the bees observed in their study were worker bumble bees, whereas we observed 100% queens. In their publication they also cite bumble bee observations in blueberries from other studies as follows: 0.04 bees per min in upstate NY, 0.55 bees per minute in the Fraser Valley of British Columbia, Canada. Our numbers compare quite favorably with theses as we observed bumble bees per minute at our three locations as 1) 0.8, 2) 1.6, 3) and 4.3 in an early season count and 2.9 in a late season count (Table 4).

Rao and Stephen (2010) also reported observing significantly greater numbers of bumble bee workers (100%) in Red Clover seed production fields. In the early bloom stage of red clover 0 to 4 bumble bees were observed per minute. However at peak bloom 15 to 30 bees were observed per minute. Rao and Stephen go on to discuss the benefits of two crop systems that complement life cycle of bumble bees; Blueberries providing forage in the spring for the queens and some early workers, and red clover providing forage in the summer for the now established annual colonies.

2. Determine critical parameters of nesting habitat for these identified species
Andrenid bees or Mining bees nest in the ground. We observed that they did not have a soil preference and built nests in soil types that varied from loamy sands, to sandy loams, to silt loams. These bees do an excellent job of camouflaging their nest entrances. We have videos and still photos of this phenomenon. One practically needs to be present when the bee enters her nest to discover and validate the hole in the soil as a nest entrance.
Bumble bees do not mine their own nest but rather use other sites such as rodent holes in which to build their nests. Bumble bees are strong flyers and have been seen to leave fields climbing to a height of 30 or 40 feet and disappearing into the distance. These bees are also secretive and it is a challenge to locate their nests (S. O’Connor et. al. 2012). Bumble bees are quite adaptable in terms of nest location. On one farm the various barns served to provide nest sites. The bumble bee queens would enter the barn through spaces between the adjacent siding boards. They would find a location that hadn’t been disturbed in years, according to the owners, and build their nests. We observed a B. auricomus continually visiting one such location. We decided not to disturb her. Other Bombus species would nest in the space between the upper floor surface and the lower floor ceiling. They simply crawled into the space and pushed away the insulation to create a hollow chamber serving as a nest site. We would see the bumble bee queens coming and going through holes in the ceiling as well as through the siding slats of the barn.

We will continue to pursue this topic this coming spring as our grant has been extended to September 30, 2017.

3. Develop recommendations for native bee nesting habitat for fruit & vegetable growers
For Andrena species our recommendation is to locate nests and designate them and areas not to be disturbed. We hope to attempt to mimic some of these locations and expand the nesting area. One farmer has expressed interest in pursuing this.
For bumble bees the barn solution has several advantages. These sites are off the ground and thus not subject to rain ice and snow. Batting insulation is an excellent choice for nesting bumble bees. A number of different artificial bumble bee nests have been created but the adoption rate by bumble bees is quite low. Our strategy is to see where they nest and then see if it makes sense to attempt to create more of the same.

4. Develop a suggested plant list specific to each crop which will provide forage outside the flowering window of the crop and meet the needs of the identified pollinators
We are in the process of creating two forage lists: One for the Andrena species and another for the Bumble bee species.

The two species of Andrena some of the earliest bees to emerge in the spring and thus would need pollen and nectar from plants flowering before blueberry. In addition their lifecycle continues for several weeks after blueberry flowering and would need pollen and nectar from plants flowering right after blueberry. Some preliminary recommendations are listed below.

A preliminary recommendation for plants flowering before blueberry is as follows: Willow, Red Maple, Magnolia, Currant, Gooseberry, Cherry (several Prunus species), and Apple.
A preliminary recommendation for plants flowering after blueberry is as follows: Zizia, Baptisia, Wild mustards, Penstemon, Chives, Wild roses, Milkweeds, and Culver’s root.

Bumble bee species create annual nests and are therefore present from early spring to frost. We are seeing the queens of these colonies and thus the numbers of worker bees could be in the range of 100 to 200 individuals per hive. Also considering that our 30 minute sample likely represents a small percentage of the actual population, some participating farms would need to provide forage for 10s of thousands of bumble bees. Providing for this many bees would certainly exceed the forage available on the farm. Thus we are of the opinion that the areas surrounding the farm are critical in providing forage to support for the colonies created by this population of queen bumble bees.

We will also be considering this aspect of the study this spring and through the summer.

5. Develop a video demonstrating nesting habitat recommendations
To be developed and submitted on September 30, 2017

6. Develop a video demonstrating forage recommendations
To be developed and submitted on September 30, 2017

Karl Foord SARE Report 3 2017 Tables Karl Foord SARE Report 3 2017 References

A presentation showing preliminary data from this project was made at the Upper Midwest Fruit and Vegetable Growers Conference on January 14, 2016. A presentation of findings through the 2015 and 2016 field seasons was made at the Upper Midwest Fruit and Vegetable Growers Conference on January 19, 2017. Actual presentations will be included in pdf format as an appendix to the annual report due on March 1, 2017. The Upper Midwest Fruit and Vegetable Growers Conference managed by the Minnesota Association of Fruit and Vegetable Growers (MFVGA).

Presentation to MFVGA attached.

An additional professional audience received this information at the Rural Advantage 3rd Crop Producer Meetings held in Fairmont, MN. Presentations were made on 3/21/2016, and 2/27/2017.

A presentation was also made to academic professionals as part of the Great Lakes Vegetable Working Group on 2/28/2017.

Although the primary audience of this grant is fruit farmers, findings from this research have been incorporated into a number of presentations made to non-professional audiences as follows:
3/2/16 – Minnesota Landscape Arboretum staff Meeting, Chanhassen, MN
3/4/2016 – Chaska Scott County Master Gardeners Garden Fever Spring Horticulture Day, Chaska, MN
3/12/2016 – Isanti County Horticulture Day Keynote, Cambridge, MN
4/6/2016 – Lamberton Horticulture Day, Southwest Research and Outreach Center (SWROC ) University of Minnesota, Lamberton, MN
4/23/2016 Lyon County Master Gardeners Garden Day, Marshall, MN
10/28/2016 9th Grade Biology Class of Moorestown Friends School, Moorestown, NJ
11/4/16 & 11/21/16 Thomas Pryce Lego League, Minneapolis, MN
Upcoming
3/25/2017 Stearns County Garden Education Day
5/10/2017 Hymenoptera Working Group U of MN Entomology

Grant extension timeline – attachedKarl Foord SARE Report 3 2017 Grant Extension Timeline

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