Final Report for OS13-081
Project Information
Honeybees contribute $15 billion in pollination services annually. Reliance on a single insect species, the honeybee, for the pollination of over 1/3 of the human food supply can be dangerous. Alternative pollination strategies that are less dependent on the honeybee must be developed in order to ensure long-term sustainably of insect pollinated crops.
The best alternative to honeybees is the native bees already present in the local environment. Therefore, research is needed to determine which native bees are present in a given region and how best to enrich the habitat (e.g. nesting areas) to increase target native bee populations.
Our studies have identified the mining bee, Andrena crataegi, and its close relatives, the Melandrena, as being the ideal native bee species for Georgia Apple production. It is time to expand the study to the next step: (1) to estimate the native population sizes in the orchards, and (2) to develop habitat enrichments and other strategies to increase the abundance of these target native bees in the apple orchards.
By establishing a strong network of native bees in Georgia agriculture, we can make Georgia agriculture more secure and sustainable. In addition, an increase in reliance on native bees means that farmers will spend less money on pollination services, which will result in greater farmer profits and potentially reduce food costs for the general public.
Introduction
Honeybees contribute $14.6 billion in pollination services to U.S. commercial agriculture annually [1]. The yields of some crops decrease by more than 90% when honeybees are not present [2]. Reliance on a single insect species, the honeybee, for the pollination of over 1/3 of the human food supply can be dangerous [3]. Indeed, this is especially true considering that honeybees are in decline from Colony Collapse Disorder (CCD), thus putting the global food supply at risk. Today, honeybee colonies are down by 40% compared to colonies available in the 1970’s [4,5]. In 2007, CCD resulted in sharp declines in honeybees in at least 35 states, including Georgia. In the affected areas, 50% of beekeepers reported significant colony losses [6].
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 [6]. The potential loss or reduction of the honeybee can have a devastating effect on agricultural production. Alternative pollination strategies that are less dependent on the honeybee must be developed in order to ensure long-term sustainably of insect pollinated crops.
The best alternative to honeybees is the native bees already present in the local environment [7-11]. With nearly 3500 species in North America alone, the diversity of different forms, pollen-strategies, and behaviors of native bees provide a wide range of use for agricultural operations. It is estimated that native bees already annually contribute $3 billion to U.S. agriculture [12].
In addition, native bees may exhibit much greater pollination efficiency compared to honeybees [13]. For example in apple pollination, one female Osmia cornifrons is estimated to pollinate 2450 apple per day, compared to 80 apples per day by a honeybee [14].
Every region, even every crop, has its own characteristic group of native bee pollinators. Data concerning regional make-ups of these native pollinator-guilds are severely lacking, which has led to our reliance on the European honeybee. In fact, across the continent, available information on native bees is spotty at best [15]. Therefore, research is needed to determine which native bees are present in a given region and how best to enrich the habitat (e.g. nesting areas) to increase target native bee populations.
Our studies have identified the mining bee, Andrena Crataegi, and its close relatives, the Melandrena, as being the ideal native bee species for Georgia Apple production. Other excellent apple pollinating native bees indentified were carpenter bees (Xylocopa virginica) and mason bees (Osmia species). It is time to expand the study to the next step: (1) to estimate the native population sizes in the orchards, and (2) to develop habitat enrichments and other strategies to increase the abundance of these target native bees in the apple orchards.
As mentioned previously, each geographic region has its own unique native bee species make-up. The mining bees (Family Andrenidae) are likely to be the main native bee group useful in pollinating early flowering fruits and vegetables in the Southeastern United States. The high clay content in the soils of the Southeastern United States has created ideal nesting sites for mining bees, resulting in large abundances of mining bees. In other areas of the U.S., such as the west coast, native bee research has focused on mason bees (Osmia species). In order to provide farmers with the most reliable scientific and agricultural information, field studies must be performed regionally.
By establishing a strong network of native bees in Georgia agriculture, we can make Georgia agriculture more secure and sustainable. In addition, an increase in reliance on native bees means that farmers will spend less money on pollination services (e.g. renting honey bee hives), which will result in greater farmer profits and potentially reduce food costs for the general public.
Literature Cited
1. 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.
2.Watanabe, M. 1994. Pollination Worries Rise as Honey Bees Decline. Science 265 (5176): 1170.
3. 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.
4. USDA National Agricultural Statistics Service. 1977. 1976 Honey production report. United States Department of Agriculture, Washington DC.
5. USDA National Agricultural Statistics Service. 2006. 2005 Honey production report. United States Department of Agriculture, Washington DC.
6. Johnson, R. 2007. Recent honeybee colony declines. CRS Report to Congress.
7. 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.
8. 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.
9. 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.
10. 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.
11. 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.
12. Losey J.E., and M. Vaughan. 2006. The Economic Value of Ecological Services Provided By Insects. Bioscience 56:311-323.
13. Sampson, B.J., S.J. Stringer, J.H. Cane, and J.M. Spiers. 2004. Screenhouse evaluations of a mason bee Osmia ribifloris (Hymenoptera: Megachilidae) as a pollinator for blueberries in the southeastern United States. Small Fruits Review 3:381-392.
14. Parker, F.D., S.W.T. Batra, and V.J. Tependino. 1987. New pollinators for our crops. Agricultural Zoology Reviews 2: 279-304.
15. National Academy of Science. 2007. Status of pollinators in North America. National Academies Press, Washington, DC.
For the 2014 field season, we have 3 main objectives.
The first objective is to gain a better understanding of native bee population sizes and their distribution in the orchards.
The second objective is to develop habitat enrichments to boost the abundance of specific native bee species.
The third objective is to survey native bee abundance and diversity in the apple orchards. Native bee diversity and abundance shift during the apple bloom and can vary depending if very early or late apple bloom periods occur.
Research
Objective 1 – Measuring Native Bee Population Numbers and Determining Their Distribution in the Orchards
We will use the technique of mark and recapture method to estimate population numbers of target native bees in the apple orchards. Using a modified version of this technique (using bee paint of different colors to denote different areas in the apple orchards), we will be able to determine bee ranges and distributions in the orchards.
N =MC/R
N = Estimate of total population size
M = Total number of animals captured and marked on the first visit
C = Total number of animals captured on the second visit
R = Number of animals captured on the first visit that were then recaptured on the second visit
Objective 2 – Boosting Target Native Bee Abundances with Nesting Habitat Enrichments
In order to boost the abundance of the target native bee species, the mining bees (Andrena Crataegi and other Melandrena species), nesting habitat enrichment sites will be created on one side of the orchard. Trenches excavated will be 4 feet long x 2 feet wide x 12 inches deep. Mining bees prefer patches of soil in which to dig tunnels for their habitat and a place to brood their young. In addition, early blooming plants (e.g. cherry trees) will be placed just behind the trenches to recruit native bees to the orchard before the apple trees even flower. Based on our previous studies, floral enrichments and bare-soil trenches should attract mining bees. In order to assess the success of the enrichments for boosting the abundance of mining bees, we will examine the trenches for holes (entrances to new colonies). We will also compare native bee abundances on the nesting habitat enrichment side of the orchard with the other sides that did not receive enrichments.
In order to boost the abundance of the secondary target bee species (mason bees), eight special nesting boxes will be created within each plot. The center of three of the eight nesting boxes will contain a large section of about sixty tubes (prime nesting sites for mason bees) and a fourth nesting box will contain a wooden block with 7mm nesting holes drilled into it. Paper tubes (6mm, 7mm, 8mm) and wooden reeds (5mm-10mm) will be randomly bundled together in groups of 60 nesting tubes. The success of the collection tubes in the nest boxes for boosting the abundance of mason bees (Osmia species) will be measured by mason bee nesting rates and the number of larvae laid in the nesting tubes. We will examine each individual tube to get an exact count and size of the mason bee larvae/pupa in each tube. This examination will not harm the developing bee.
Objective 3 – Survey of Native Bees in Georgia Apple Orchards
The third main objective is to continue the survey of the native bee pollinators for a fifth year within the apple orchards, with a focus placed specifically on the apple bloom periods. Significant weather changes, perhaps due to global warming, have resulted in drastically different growing seasons in the past four years. In 2010, the apple bloom exhibited a traditional pattern of blooming in early to mid-April. The apple bloom shifted 4-5 weeks earlier in 2011 and 2012 from the typical bloom. These much earlier apple blooms were pollinated by a different composition of native bees. For example, mason bees, (Osmia species) were more abundant during early apple blooms. In 2013, the apple bloom occurred two weeks late (late April), resulting in fewer mason bees but more mining bees.
In these orchards, native bees will be 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 will be measured 2 weeks prior to and after the bloom, and weekly during the bloom itself. The traps will be set up around dawn and will remain up until after dusk during collection days, which is a typical 12-hour collection period.
At each orchard, there will be a total of 13 sets of pan-traps. Each set includes 1 white, yellow, and blue pan painted with UV-reactive paint. In each orchard, 6 sets of vane traps will be used. Each set includes 1 blue vane trap and 1 yellow vane trap. Likewise, 3 malaise traps will be set-up (1 trap in the center of the orchard with the other 2 traps near the edge of the plot) for each sample day.
After the collection, all the bees will be brought back to the GGC laboratory to be counted and identified. Bees will be determined to species and either preserved in ethanol or pinned and mounted in permanent collection boxes.
Objective 1 – Measuring Native Bee Population Numbers and Determining Their Distribution in the Orchard
In the first objective, we estimated the population size of Andrena crataegi at Mountain View Orchard using the standard mark and recapture method. This measurement took place during the apple bloom on April 19, 2014. We began by marking 187 bees with yellow UV powder in the Northwest quarter of the plot, 110 bees with blue UV powder in the Southwest quarter of the plot, 173 bees with red UV powder in the Northeast quarter of the plot, and 247 bees with white UV powder in the Southeast quarter of the plot. After a very brief confinement (less than 1 minute) in a powder jar, the bees were released. We recaptured the bees seven days later. We recaptured 1078 bees (930 males and 148 females). It was not possible to sex the bees quickly enough during the powdering stage. After examining the bees, we discovered 4 blue powdered, 11 white powdered, 11 white powdered, and 0 red powdered bees. We are unsure why 0 red powdered bees were recapture, perhaps the UV light we used had difficultly picking up red UV powder. Using the standard mark and recapture formula, we calculated the following population estimates: 18,326 bees based on the yellow powder, 29,645 bees based on the blue powder, and 24,206 bees based on the white powder. If we average the three values we get an estimate population size of 24,059.
We repeated the mark and recapture experiment the following week at an Andrena crataegi’s huge communal nesting area. The communal nesting area occupied to rows of apple trees. In each row, the commune with hundreds of entrance holes, measured 20 meters x 3 meters in length. The estimate population size of the Western commune was 2,213 bees.
Objective 2 – Boosting Target Native Bee Abundances with Nesting Habitat Enrichments
In the mining bee artificial habitats (48 inch x 24 inch trenches with bare soil exposed), significant mining bee nesting was measured. Mining bees (Andrena species) dig tunnels in the soil and use the tunnels as their nest sites. Some mining bees are communal and live in large groups, while other mining bees are solitary, with each female making her own nest. Nesting rates were measured during a two-week period during the apple bloom. Nesting rates in the artificial habitats averaged 39 new nesting tunnels per artificial habitat. Most of the new nesting tunnels belonged to Andrena crataegi. So, each of these nesting tunnels would likely be used by multiple bees.
Previous nesting at the habitat had no effect on future nesting, and the presence/absence of floral resources (food) did not appear to make a difference. The only difference measured was a mining bee preference to nest in the side of the trench instead of the bottom of the trench. The bees preferred the side nesting area 2 to 1 compared to bottom of the trench nesting areas.
In the mason bee artificial habitats (paper tubes and wooded reed tubes in wooden boxes), significant mason bee nesting was measured. The most common species observed nesting in the artificial nesting tubes were Osmia georgica and Osmia taurus. There were 760 artificial nesting tubes or holes to nest in. 41 of the tubes were nested in by O. georgica, and 6 tubes were nested in by O. taurus. Tubes with O. georgica exhibited a high percentage (71%) of parasites that killed all the mason bee larvae in the tube. This parasitism was strongly correlated to paper tube vs. wooden reed nesting use. O. taurus exhibited no parasite problems.
Osmia georgica showed a strong preference for the smaller (6 mm) tube size. Osmia taurus showed a strong preference for the larger (8 mm) tube size. On average, O. georgica laid 9.6 larva per tube and had an average pupa size of 5.7 mm. The pupa cocoon of O. georgica was tighter packed in construction and had orange coloration compared with the fluffy brown cocoons of O. taurus. On average, O. taurus laid 10.3 larva per tube and had an average pupa size of 7.9 mm.
A total of 116 O. georgica and 62 O. taurus adults hatched out of the tubes. O. taurus hatched roughly 2 weeks (beginning March 1) before O. georgica. These bees were successfully released in their home orchards in March 2015.
Objective 3 – Survey of Native Bees in Georgia Apple Orchards
During the 2014 growing season (March-September), 3374 bees from 28 Genera were collected during the survey. The 3 most common native bee groups were Genus Andrena (mining bees) (43.6% of the sample), Genus Lasioglossum (sweat bees) (24.1% of the sample), and Genus Bombus (Bumblebees)(4.1% of the sample). Honeybees (Apis mellifera) made up 7.6% of the sample. Andrena crataegi continued to be the most common bee species collected in the apple orchards. See Table 1 for more information.
Educational & Outreach Activities
Participation Summary:
One of the best methods to interact with famers and the public is through the “Native Bees of Georgia” website that was created as part of this project. The website is found at http://native-bees-of-georgia.ggc.edu/ . The website provides a photograph based identification key to the native bees found in Georgia, as well as information of agricultural benefit, life history, and features of the major groups of bees.
Schlueter, M.A. and N.G. Stewart. An Assessment of Native Bee Diversity and Abundance in North Georgia Apple Orchards from 2010-2014. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Schlueter, C.G. and M.A. Schlueter. An Examination of Hoverfly (Family Syrphidae) Diversity and Collection Methods in Georgia Apple Orchards. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Schlueter, P.M., N. G. Stewart, and M.A. Schlueter. Osmia Taurus, O. Cornifrons, and Anthidium Manicatum in North Georgia: Three Introduced Bee Species Making Their Way Down South. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Schlueter, C.G. and M.A. Schlueter. A Survey of Hoverfly (Family Syrphidae) Diversity and Abundance in North Georgia. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Schlueter, M.A. and N.G. Stewart. A Five-Year Survey of Native Bee Diversity and Abundance in North Georgia. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Schlueter, P.M., N. G. Stewart, and M.A. Schlueter. Nesting Habits of Introduced and Native Mason Bee Species (Osmia species) in North Georgia Apple Orchards. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015.
Stewart, N.G. and M.A. Schlueter. An evaluation of Georgia’s mason bees (Osmia species) and their nesting preferences. 91th Annual Meeting – Georgia Academy of Science. Augusta, GA. March 28-29, 2014.
Schlueter, G.C., N.G. Stewart. and M.A. Schlueter. Observing and Measuring the Pollination Effectiveness of Andrena Crataegi and other bees in Commercial Apple Orchards. 91th Annual Meeting – Georgia Academy of Science. Augusta, GA. March 28-29, 2014.
Schlueter, M.A. and N.G. Stewart. The mining bee, Andrena crataegi, a potential new commercial pollinator. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Stewart, N.G. and M.A. Schlueter. Temporal patterns of the apple bloom impacts the abundance and diversity of native bees. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Rodriguez, T., S. Brown, M. Coger, N. Stewart and M. Schlueter. A comparison of pollination behaviors in bumble bees, carpenter bees, mining bees, and honey bees on apple and blueberry flowers. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Schlueter, G.C., N.G. Stewart. and M.A. Schlueter. The identification of Andrena crataegi as the apple bee in Georgia. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Stewart, N.G. and M.A. Schlueter. Diversity and abundance of native bees in orchards are significantly impacted by the timing of the apple bloom. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Rodriguez, T., S. Brown, M. Coger, N. Stewart and M. Schlueter. Native bee pollination behaviors and pollen load measurements. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013.
Stewart, N.G. and M.A. Schlueter. Fluctuations in Species Abundances of Major Apple Pollinating Native Bees During Progessively 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.
Stewart, N.G. and M.A. Schlueter. Mason Bee (Megachilidae:Osmia) Abunadance 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.
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.
Project Outcomes
This project has identified the native bees with the greatest potential to replace or supplement honeybees in apple pollination in Georgia. We successfully developed procedures and methods to increase the abundance of these target native bees. The current project has shown that by providing habitat enrichments (e.g. nesting sites), we can boost native bee abundance. Once researchers have developed a methodology to maximize the abundance of target native bees for a broad range of Georgia crops, we can state sustainable agriculture in Georgia is safeguarded. By establishing a strong network of native bees in Georgia agriculture, we can make Georgia Agriculture more secure and sustainable. In addition, an increase in reliance on native bees means that farmers will spend less money on pollination services (e.g. renting honey bee hives) that will increase farmer profits and potentially reduce food costs for the general public.
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 [4,5]. 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 our experimental orchards have observed 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 next several growing seasons, the farmers have agreed to allow the placement of several different experimental nesting habitats. Also, the farmer cooperators 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.
Areas needing additional study
Results from this project and from other studies have 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, mining bees (Andrena species), bumblebees (Bombus species), carpenter bees (Xylocopa species) and mason bees (Osmia species). Results from this study illustrate that habitat modification can boost native bee abundance. The next step is to continue to develop and test appropriate habitat modifications (supplemental nesting sites, additional pre-bloom floral resources) 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.