Native Bee Assessment in North Georgia Apple Orchards: Measuring Diversity and Devising Methods to Boost Abundance

Final Report for OS12-066

Project Type: On-Farm Research
Funds awarded in 2012: $15,000.00
Projected End Date: 12/31/2013
Grant Recipient: Georgia Gwinnett College
Region: Southern
State: Georgia
Principal Investigator:
Dr. Mark Schlueter
Georgia Gwinnet College
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Project Information

Abstract:

European Honeybees (Apis mellifera) play a vital role in pollinating the majority of all human agriculture. Becoming so dependent upon a single species to pollinate such a large facet of food production has proven unsustainable, especially as worldwide declines intensify. Since 2006 alone, a 30% reduction in managed colonies of honeybees in North America has placed much of Georgia’s agriculture at potential risk by lowering crop yields and by increasing pollination costs (renting honeybee hives). Failure to act now could lead to future issues without the capital or time required to uncover adequate solutions.

It is prudent to find possible solutions and alternatives before a serious crisis develops. To safeguard Georgia agriculture, researchers must not only look for answers to Colony Collapse Disorder (CCD), but they must also devise alternatives to the honeybees if researchers fail to fix CCD and the other issues decimating honeybee populations.

One possible alternative to using honeybees is to use native bees for pollination services. Native bees could be used to supplement or replace the honeybee in the pollination of a specific crop. To investigate the potential native bees have for supporting commercial agriculture, a three-step approach must be taken. Step one is to perform native bee species surveys in order to know which species are present in a given farm or orchard. Step two is to identify specific native bees as potential target pollinators for certain cultivated plants. Step three is to perform minor habitat modifications to increase the abundance of the target native bees.

The current project has addressed steps 1 and 2. For step one, we have characterized the native bee species diversity and abundance in Georgia Apple Orchards over the past three years (2010-2012). For step two, we have confirmed the target native bee pollinators in Georgia Apple Orchards. We have identified Andrena crataegi as the “Georgia Apple Bee”. Other excellent bee pollinators in Georgia apple orchards were the mining bees in the sub-genus Melandrena, bumblebees, and carpenter bees.

Introduction

Honeybees (Apis mellifera L.) are a vital part of human agriculture. It is estimated that bees pollinate approximately one-third of all human food crops [1]. In the United States alone, bees pollinate about 130 agricultural plants [2,3]. To get high crop yields, most farmers rent honeybee hives from beekeepers to boost the number of bees pollinating their crops. It is estimated that the value of honeybee pollination to U.S. agriculture in 2000 was $14.6 billion [4,5].

Worldwide agricultural operations, however, are facing a growing dilemma that has the potential to jeopardize traditional farming practices and ultimately affect food production: the unprecedented decline of the European Honeybee (Apis mellifera). Especially prominent in the Western Hemisphere since the mid-1990s, Colony Collapse Disorder (CCD) threatens to decrease production of such staple fruit crops as peaches, almonds, cherries, and, of specific focus to this study, apples [6].

The first European honeybee (Apis mellifera) colony was imported in Jamestown sometime in 1621. Since that time, the honeybee has been the main commercial pollinating insect in the United States. However, since the 1970s and especially during the late 1990s, there has been a gradual escalating decline in the number of European honeybee colonies maintained by U.S. beekeepers. This phenomenon and the near complete disappearance of feral/wild colonies have led to great concern in the U.S. [7]. Beginning in 2006, the rate of attrition reached even higher proportions, and beekeepers reported unprecedented losses of 30-90% of their hives during the winter of 2006 [3]. At this time, the term "colony collapse disorder" was proposed to describe the sudden disappearances of bees. The decline of European honeybee colonies is blamed on a number of effects, including a fungus specific to Old World honeybees (all 7 Apis sp.), certain pesticides developed specifically for social insects (fiprinil, imaldicprid), exponential urbanization, and the overall drop in North American apiculturalists. The most important reason for the decline, however, is attributed to an introduced mite common to Asian Honeybee (Apis cerulae) colonies [8-10].

Several studies have shown that reductions in the supply of commercial honeybee stocks can result in significant declines in overall crop yield [11] if no alternate pollination sources are utilized. Some scientists have also predicted a potential disaster to the global food supply that will be brought about by a global pollination crisis. These scientists predict economic instability due to increased costs of food and the potential for famine [6]. Because of these dire consequences, the identification of alternative insect pollinators to replace or supplement European honeybees must be of paramount priority to the U.S.

Honeybees, however, are not responsible for 100% of the pollination of agricultural crops. An untapped solution common to every agricultural site is the incredibly diverse assortment of native bees [12]. Many of the species within this broad community have great potential to supplement or replace the dwindling honeybee as the primary pollinator for many diverse crops, with little more than simple habitat alterations [13].

Several studies [13-17] suggest these native bees may be the answer to our problem. Native bees account for the bulk of pollination activities in natural and cultivated areas throughout the world [14-17]. With nearly 3500 species in North America alone, the diversity of different forms (size, pubescence, etc.), pollen-strategies, and behaviors (early spring emergence, prolonged daily foraging, shorter inter-flower travel, etc.) of native bees provide a wider range of use for agricultural operations compared with the traditional work-horse, the European honeybee [12-17]. However, data concerning regional make-ups of these native pollinator-guilds are severely lacking, which has led to our reliance on the European honeybees. In fact, spotty information on native bees is available across the continent at best. Therefore, research is needed to determine if native bees can be efficient pollinators of commercial crops. Moreover, studies need to be conducted to determine which native bees are the most important pollinators and how effective native bees are at pollinating Georgia food crops.

We began investigating the native bees present in North Georgia apple orchards during the 2010 growing season. During the 2010 survey, we documented 129 bee species. Many of these native bee species were found to be abundant in Georgia apple orchards. These facts have led to the hypothesis that native bees have the potential to either supplement or replace the dwindling honeybee in Georgia’s commercial agriculture (e.g. apples).

LITERATURE CITED

1. Klein A.M., B.E. Vaissiere, J.H. Cane, I. Steffan-Dewenter, S.A.Cunningham, and C. Kreman. 2007. Importance of Pollinators in Changing Landscapes for World Crops. Proceedings of the Royal Society B: Biological Sciences 274: 303–313.

2. Delaplane K.S. and D.F. Mayer. 2000. Crop Pollination by Bees. CAB International, Oxon, United Kingdom, 344 pp.

3. Kaplin, J.K. 2008. Colony Collapse Disorder: A Complex Buzz. Agricultural Research. May-June 2008: 8-11.

4. Morse R.A. and N.W. Calderone. The Value of Honey Bees as Pollinators of U.S. Crops in 2000. Bee Culture 128:1-15.

5. Losey J.E., and M. Vaughan. 2006. The Economic Value of Ecological Services Provided By Insects. Bioscience 56:311-323.

6. Aizen, M.A., L. A. Garibaldi, S. A. Cunningham, and A. M. Klein. 2009. How Much does Agriculture Depend on Pollinators? Lessons from Long-Term Trends in Crop Production. Annals of Botany 103: 1579–1588.

7. Kluser S. and P. Peduzzi P. Global Pollinator Decline: A Literature Review. 2007. Geneva: UNEP/GRID.

8. Watanabe, M. 1994. Pollination Worries Rise as Honey Bees Decline. Science 265 (5176): 1170.

9. Stubbs, C.S. and F.A. Drummond (Ed). 2001. Bees and Crop Pollination – Crisis, Crossroads, Conservation. Thomas Say Publications in Entomology, Entomological Society of America, Lanham, MD, 156 pp.

10. Batra, S.W.T. 1995. Bees and Pollination in Our Changing Environment. Apidologie 26: 361-370.

11. Ricketts, T.H., G.C. Daily, P.R. Ehrlich, and C.D. Michener. 2004. Economic Value of Tropical Forest to Coffee Production. Proceedings of the National Academy of Sciences USA 101:12579-12582.

12. Bartholomew, C.S., D. Prowell, and T. Griswold. 2006. An Annotated Checklist of Bees (Hymenoptera: Apoidea) in Longleaf Pine Savannas of Southern Louisiana and Mississippi. Journal of the Kansas Entomological Society 79(2): 184–198.

13. Kremen, C., N.M. Williams, and R.W. Thorp. 2002. Crop Pollination from Native Bees at Risk from Agricultural Intensification. Proceedings of the National Academy of Sciences of the United States of America 99 (26): 16812-16816.

14. Chagnon M., J. Gingras and D. de Oliveira. 1993. Complementary Aspects of Strawberry Pollination by Honey Ad Indigenous Bees (Hymenoptra). Journal of Economic Entomology 86:416-420.

15. DeGrandi-Hoffman, G. and J.C. Watkins. 2000. The Foraging Activity of Honey Bees (Apis mellifera L.) and Non-Apis Bees on Hybrid Sunflowers (Helianthus annuus L.) and its Influence on Cross-Pollination and Seed Set. Journal of Apic Research 39:37-45.

16. Greenleaf S.S. and C. Kreman. 2006. Wild Bees Enhance Honey Bees’ Pollination of Hybrid Sunflower. Proceedings of the National Academy of Sciences USA 103(37): 13890-13895.

17. Kremen C., R.L. Bugg, J.P. Fay, and R.W. Thorp. 2004. The Area Requirements of an Ecosystem Service: Crop Pollination by Native Bee Communities in California. Ecology Letters 7:1109-1119.

18. Johnson, R. 2007. Recent honeybee colony declines. CRS Report to Congress.

Project Objectives:

OBJECTIVE 1 – Survey of Native Bees in Georgia Apple Orchards
A survey of native bees was conducted (March to September 2012) in four North Georgia Apple Orchards. Native bee species diversity and abundance before, during, and after the apple bloom was measured. This was the third year of the native bee survey. Long-term studies have the ability to assess the effects of weather (e.g. rainfall, global warming), and bloom period (e.g. early vs. late) on native bee populations, as well as measure shifts in native bee populations.

OBJECTIVE 2 – Measuring the Success of Native Bees in Apple Pollination.
The effectiveness of native bees to pollinate apple trees was investigated using netting enclosures. The netting enclosures allowed native bees access to the apple flowers. However, the netting prevented honeybees access to the apple flowers on select trees. Four different measurements of pollination success were taken: (1) percent of flowers pollinated, (2) the effectiveness of pollination on each flower (determined by seed count), (3) number of apples produced per branch, and (4) average size of apples produced.

OBJECTIVE 3 – Determine the Potential Usefulness of Nest boxes in Boosting Native Pollinator Abundance.
Small orchards surrounded by areas of natural vegetation have a much larger abundance of native bees than larger orchards (e.g. Mercier Orchards) (Schlueter and Stewart, unpublished data). For example, the Mountain View Orchard is a typical small-scale orchard surrounded largely by natural vegetation (continuous tracts of habitat impacted little by humans). Mercier Orchards, alternatively, is a large-scale orchard surrounded by limited natural vegetation, fragmented by human activity through agricultural and residential operations. Due to its massive orchard area (the largest orchard in GA, with over 215,000 apple trees), we have found that this orchard has a reduced diversity and number of native bees; particularly as you move to the center of the orchard. Can nest boxes help boost native pollinator abundance?

During this year of the study, we assessed whether the mining bees (Family Andrenidae) will use nest boxes filled with sand/loam mixtures. Andrenids were our target group because our data suggests that they are the most important group of native bees for apple pollination.

Cooperators

Click linked name(s) to expand
  • Dr. Mark Schlueter
  • Nicholas Stewart

Research

Materials and methods:

OBJECTIVE 1 – Survey of Native Bees in Georgia Apple Orchards
In these orchards, native bees were collected using several types of insect collecting traps and procedures, including pan-traps, vane-traps, malaise-traps, and timed sweep-netting. Insect diversity and abundance were measured weekly during the apple bloom and every 2 weeks just before and after the apple bloom. The sites were measured monthly from May to October. The traps were set up around dawn and remained up until after dusk during collection days, which was typically a 12-hour collection period.

The four orchards surveyed were: Mountain View Orchards (2984 Mobile Road, McCaysville, GA 30555) Mercier Orchards (8660 Blue Ridge Drive, Blue Ridge, GA 30513) Hillside Orchards (105 Mitcham Circle, Tiger, GA 30576) Tiger Mountain Orchards (1309 Bethel Road, Tiger, GA 30576).

After sampling, the bees were brought back to the GGC laboratory to be counted and identified. Bees were determined to species and either preserved in ethanol or pinned and mounted in permanent collection boxes. Difficult and rare bee species identifications were checked and verified by Sam Droege (U.S. Native Bee Lab, U.S. Geological Survey, Patuxent Research Center). The University of Georgia Natural History Insect Collection and Sam Droege's native bee collections were also used in specimen identification verifications.

OBJECTIVE 2 – Measuring the Success of Native Bees in Apple Pollination
In the following experiment, ten apple trees were randomly selected at Mountain View Orchard. In each selected tree, branches of the tree were enclosed with small mesh netting enclosure that excluded commercial honeybees from entering the enclosure and pollinating the flowers of the selected apple tree. Based on our preliminary research (2010 field season in the apple orchards), we determined that over 80% of native bee species are smaller than the commercial European honeybees. Small size native bees were able to enter the netting and perform pollination activities. In each enclosure, a large pan trap was placed inside to collect a sample of all the native bees that entered the enclosure prior to, during, and after the apple bloom. The enclosures were placed over the trees several weeks prior to the apple bloom and removed after 95% or more of the apple flowers fell off the apple tree.

Four different measurements of pollination success were taken during the apple season. These measurements included: (1) percent of flowers pollinated, (2) the effectiveness of pollination on each flower (determined by seed count), (3) number of apples produced per branch, and (4) average size of apples produced. For each selected tree, we compared the enclosed branches (experimental group) with similar sized unenclosed branches (control group) on the same tree.

OBJECTIVE 3 – Determine the Potential Usefulness of Nest boxes in Boosting Native Pollinator Abundance
In this experiment, we assessed whether the mining bees (Family Andrenidae) will use nest boxes filled with sand/soil mixtures (Xerces Society – www. Xerces.org). Andrenids were the target group based on last year’s sampling data. The data suggested that the mining bees were the most important group of native bees for apple pollination.

We placed 24 nest boxes (30 gallons) in the Mountain View Orchard. Twelve next boxes were placed in the ground and 12 boxes left above ground. Several different mixtures were tested. These included: (a) native red clay based soil from the orchard; (b) 80% soil - 20% sand mix, (c) 67% soil - 33%soil mix, and (d) 100% sand (control). The nest boxes were observed weekly during the apple bloom to measure nesting rates.

Research results and discussion:

The project had three main objectives: (1) to identify the native bees present in or near North Georgia apple orchards, (2) to measure the pollination success of the native bees, and (3) to determine the potential usefulness of nest boxes in boosting native pollinator abundance.

OBJECTIVE 1 – Survey of Native Bees in Georgia Apple Orchards
During the 2012 growing season (March- October), 5091 bees were collected. Table 1 provides a summary of the 2012 North Georgia Bee Survey at four apple orchards. A total of 5,091 bees were collected representing 5 families, 40 genera, and 115 species. Specifically, 1111 bees were collected from Hillside Orchard, 352 bees were collected from Mercier Orchard, 2075 bees were collected from Mountain View Orchard, and 1553 bees were collected from Tiger Mountain Orchard. Included in these numbers are 873 honeybees (Apis mellifera). Honeybees accounted for 17.1% of the collection, while native bees accounted for 82.9% of the collection. Mountain View Orchard continued to have the largest number of native bees (Mountain View orchard did not use honeybee colonies in 2012, it relied on native bee pollination). At this orchard 97% of the bees collected were native bees. Hillside Orchard had the largest numbers of honeybees. Hillside Orchards maintain a large number of permanent honeybee colonies located on the farm used in honey production for its country store. In this orchard 42% of the bees collected were honeybees (466 honey bees compared with 645 native bees).

There were 115 different bee species identified. The most abundant bee taxa identified were: Andrena (mining bees), Lasioglossum (sweat bees), Xylocopa (large carpenter Bees), Ceratina (small carpenter bees), and Bombus (bumblebees).

OBJECTIVE 2 – Measuring the Success of Native Bees in Apple Pollination.
During the 2012 season of the study, we assessed the pollination success of native bees using netting enclosure on trees.

There were 10 experimental apple trees used in the study. Each tree had a netting enclosure over an experimental branch and a similar size control branch without an enclosure. The netting enclosure prevented honeybees (and bees larger than honeybees such as bumblebees and carpenter bees) from getting to the apple flowers to pollinate them. Thus, native bees preformed all the pollination of the apple flowers in the netting enclosures. Pan traps inside the netting enclosures collected 160 native bees. The most common native bees captured in pan traps within the enclosures were Andrena crataegi (72.5%) and Andrena carlini (15.7%). Table 2 lists all the native bees collected by pan traps inside the netting enclosures.

Apples were collected from 5 of the trees in mid-season (June) prior to apple drop. Control apples had a mean circumference of 17.2 cm and a mean seed count of 8.1 compared with experimental apples with a mean of 16.8 cm and a mean seed count of 7.5. Statistical analyses indicated that there were no differences between the control and experimental groups in any of these measurements.

Mature apples were collected from 5 of the trees at the end of the season in August. Control apples had a mean weight of 123.8 g, circumference of 21.3 cm and seed count of 5.9 compared with experimental apples with a mean weight of 145.2, circumference of 22.6 cm and a mean seed count of 6.9. Statistical analyses indicated that there were no differences between the control and experimental groups.

These results indicated that native bees pollinated apple trees just as well as the honeybees. Furthermore, pan traps inside the netting enclosures clearly show that Andrena crataegi (Figures 1 and 2) was the main bee performing the pollination of the apple flowers. The netting experiment confirmed the numerous field observations of A. crataegi observed interacting and pollinating the apple flowers during the apple bloom. We have observed A. crataegi females and males crawling deep within the apple flowers and even observed A. crataegi males asleep in the apple flowers. Based on the field observation and the results of the study, we have labeled Andrena crataegi, Georgia’s “apple bee”.

OBJECTIVE 3 – Determine the Potential Usefulness of Nest boxes in Boosting Native Pollinator Abundance.
During this year of the study, we assessed whether the mining bees (Family Andrenidae) will use nest boxes filled with sand/soil mixtures. Andrenids were our target bee group because our past year’s data suggests that they are the most important group of native bees for apple pollination.

Unfortunately, our results do not support the hypothesis that nest boxes will boost native bee abundance. Initially, the mining bees (Andrena species) colonized both the raised nest boxes and in-ground nest boxes. These mining bees did construct tunnels in the soil in the nest box to be used as their nests. However after less than a week, the bees abandon the nest boxes. At the same time, at the Mountain View Orchard (and also the Tiger Mountain Orchard), we observed the construction of several large Andrena crataegi nests in bare patches of dirt located under apple trees. Several other much smaller mining-bee nests (solitary bees - Andrena Melandrena species) were also observed. All of these nests had significant amount of bee activity with bees going in and out of the nests.

We believe that factors such as: (1) the small size of the nest boxes (30 gallons), (2) increased temperature of nest boxes above the ground, and (3) drainage issues after a rainfall all contributed to the failure of the nest boxes.

From our observations, we have concluded large bare earth patches (grass-free areas) are a prerequisite to mining bee colonization. These patches may be located on flat or elevated ground. The nest box experiment did show that the native bees preferred their native soil (containing red clay soil) to the other topsoil/sand mixtures.

The 2012 study’s results will assist in new designs for new nesting habitats. Preliminary designs for the 2013 season will focus on the construction of 2 X1 foot trenches. This new in-ground design will incorporate all the nesting perquisites needed by the mining bees (Andrena species).

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Stewart, N.G. and M.A. Schlueter. Fluctuations in Species Abundances of Major Apple Pollinating Native Bees During Progressively Earlier Apple Blooms Over a Three Year Period in North Georgia. 2013 Annual Meeting – Association of Southeastern Biologist. Charleston, WV. April 10-13, 2013.

Stewart, N.G. and M.A. Schlueter. Identification of a Native Bee Species to Serve as the Primary Pollinator for Commercial Apple Cultivation in North Georgia. 2013 Annual Meeting – Association of Southeastern Biologist. Charleston, WV. April 10-13, 2013.

Schlueter, C.G., N. G. Stewart, and M.A. Schlueter. An Assessment of Pollination Success by Native Bees in North Georgia Apple Orchards. 90th Annual Meeting – Georgia Academy of Science. Valdosta, GA. March 29-30, 2013.

Stewart, N.G. and M.A. Schlueter. Mason Bee (Megachilidae:Osmia) Abundance and Diversity in North Georgia Orchards from 2010-2012: The Role of Osmia During Premature Apple Bloom Conditions. 90th Annual Meeting – Georgia Academy of Science. Valdosta, GA. March 29-30, 2013.

Stewart N.G. and M.A. Schlueter. The Influence of a Premature Apple Bloom in North Georgia on the Abundance of Native Bee Species. 89th Annual Meeting – Georgia Academy of Science. Kennesaw State University, Kennesaw, GA. March 23-24, 2012.

Schlueter, M.A. and N.G. Stewart. A Multi-Year Collection Inventory of Bees and Pollinating Flies Found In North Georgia Apple Orchards: Comparing an Early Apple Bloom with a Late Apple Bloom. 59th Annual Meeting of the Entomological Society of America, San Diego, CA. Nov. 13-16, 2011.

Schlueter, M.A. and N.G. Stewart. Which Trap Type And Trap Color Work Best In Collecting Different Groups Of Bees (Family: Apidae) And Pollinating Flies (Order: Diptera)? 59th Annual Meeting of the Entomological Society of America, San Diego, CA. Nov. 13-16, 2011.

Stewart, N.G. and M.A. Schlueter. A Two-Year Comparison of Native Pollinators under Strikingly Different Seasonal Conditions in North Georgia. 59th Annual Meeting of the Entomological Society of America, San Diego, CA. Nov. 13-16, 2011.

Stewart, N.G. and M.A. Schlueter. Replacing The Honey Bee: Why Wait? Increasing Sustainable Agricultural Practices and Cost-Cutting for Small-Scale Farming. 58th Annual Meeting of the Entomological Society of America, 59th Annual Meeting of the Entomological Society of America, San Diego, CA. Nov. 13-16, 2011.

Stewart, N.G. and M.A. Schlueter. A Seasonal Survey of Pollinating Flies and Bees in North Georgia Apple Orchards. 88th Annual Meeting – Georgia Academy of Science. Gainesville State College, Gainesville, GA. March 25-26, 2011.

Project Outcomes

Project outcomes:

The 2012 study found that most Georgia apple orchards have diverse and abundant sources of native bees. Over 5000 native bees were collected at 4 North Georgia apple orchards in the 2012 growing season. To date, 181 native bee species have been identified in Georgia Apple orchards by the study’s researchers. This study has identified the target native bee species for apple pollination in North Georgia as Andrena crataegi and secondarily the bees of the subgenus Melandrena (Genus Andrena).

If methods can be developed to boost the abundance of these target native bee species, farmers can begin to shift their pollination services from the struggling honeybee to native bees. These changes will safeguard Georgia’s agriculture and will provide a more cost-efficient sustainable method of pollinating Georgia’s apple crops.

Economic Analysis

In the Unites States alone, honeybees contribute nearly $15 billion in pollination services. The yields of some crops decrease by more than 90% when honeybees are not present. The reliance on a single insect species, the honeybee, for the pollination of over 1/3 of the human food supply can be dangerous. In the United States, there has been a sharp decline in managed honeybee colonies, from 4 million honeybee colonies in the 1970’s to 2.4 million colonies in 2005.

The reduced availability of honeybee colonies has increased food production costs and reduced potential crop yields. Most farmers are dependent on rented honeybee hives in order to ensure their crops are fully pollinated. The shortage of honeybee colonies has resulted in a rapid increase in the cost of renting honeybee hives. For example, the cost of renting a single honey bee colony used in almond pollination in California increased from $35 in the early 1990’s to $150 per colony in 2007 [18].

If native bees can be harnessed as the primary pollinator, or even as a supplement pollinator of targeted food crops, farmers will reduce their production costs by reducing or eliminating the use of rented hives. Consider the annual savings if native bees can pollinate roughly half of a farmer’s crops. For example, a farmer who requires 100 rented hives for crop pollination might pay (100 hives @ $150 = $15,000) before adding habitat enrichments (e.g. nesting areas) for native bees. If the native bees provide half the pollination required, the farmer spends only $7,500 (50 hives at $150) each year on pollination services.

Farmer Adoption

Based on this study, farmers at all four orchards have seen the significant role that native bees play in the pollination of their orchards. The long-term goal of our research in shifting pollination services to native bees from honeybees is appealing to farmers because of the significant cost savings and better long-term sustainability. In order to boost the abundance of “target” native bee populations, certain habitat modifications will be necessary. The most important of these modifications is providing more nesting habitat for native bees. During the 2013 growing season, the farmers have agreed to allow the placement of several different experimental nesting habitats. Also, the farmer cooperators at all four orchards will make a special effort to implement procedures to enhance native bee abundance (particularly just before, during, and just after the apple bloom). These changes will include: reducing grass mowing of the orchard (allows wildflowers to supplement native bee food sources) and reducing pesticide use.

Recommendations:

Areas needing additional study

Past research from this project and from other studies has documented that native bees have the potential to supplement and/or replace the honeybee in commercial agriculture. This study has clearly identified which species of native bees are most suited for the pollination of commercial apple orchards in Georgia. These target bees include: Andrena crataegi, Melandrena bees, bumble bees, and carpenter bees. Other bees of interest are mason bees (Osmia species) and bumblebees (Bombus species). The next step is to develop appropriate habitat modifications (supplemental nesting site, additional pre-bloom floral resource) in order to boost the abundance of these target native bee species. If methods can be developed to boost the abundance of these target native bee species, farmers can begin to shift their pollination services from the struggling honeybee to native bees. These changes will safeguard Georgia’s agriculture and will provide a more cost-efficient sustainable method of pollinating Georgia’s apple crops.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.