Honeybees pollinate 1/3 of all human food crops. The value of honeybee pollination to U.S. agriculture is over $15 billion each year. However, agricultural operations worldwide are facing a growing dilemma that threatens food production: the rapid decline of the Honeybee.
A solution to this problem is the diverse assortment of native bees. Many of these bees have the potential to supplement or replace the dwindling honeybee as the primary pollinator for a range of crops.
The focus of the current project was to identify the native bees present in North Georgia apple orchards, and to measure their pollination success.
It is estimated that 35% of global food production is dependent on animal pollination. Animal pollination is essential or at least important in 87 of the 115 leading global crops. Insects, mainly bees, are the main animal pollinator in almost every animal pollinated crop .
Honeybees (Apis mellifera L.) are the most important insect pollinator for the majority of agriculture crops, excluding cereals. The yields of some crops decrease by more than 90% when honeybees are not present . In the Unites States alone, honeybees contribute $14.6 billion in pollination services .
Reliance on a single insect species, the honeybee, for the pollination of over 1/3 of the human food supply can be dangerous. Indeed, this is especially true considering that honeybees are in trouble, thus putting the global food supply at risk. 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 [4,5]. The losses in managed honeybee colonies and the disappearance of wild honeybee colonies has been attributed to several factors, which include increases in parasites, improper use of pesticides, genetic inbreeding, and many other factors . In 2006, the situation worsened with a significant increase in honeybee losses (30-90% of a colony). These losses were documented particularly in the East Coast of the United States, due to the phenomenon labeled Colony Collapse Disorder (CCD) [7,8]. In 2007, CCD resulted in sharp declines in honeybees in at least 35 states. In the affected areas 50% of beekeepers reported significant colony losses .
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 .
The potential loss or reduction of the honeybee can have a devastating effect on agricultural production. We need to develop alternative strategies that are less dependent on the use of the honeybee 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. There are over 17,000 bee species in the world . 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 wide range of use for agricultural operations [10,11].
It is estimated that native bees already annually contribute $3 billion to U.S. agriculture . Many native bees already play an important role in the pollination of blueberries , watermelons , and many other crops.
This natural reservoir of insect pollinators needs to be fully utilized in order to safeguard the sustainability of commercial agriculture. With little more than simple habitat alterations to encourage native bee colony growth, many native bee species have great potential to supplement or replace the dwindling honeybee as the primary pollinator for many diverse crops .
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 honeybees. In fact, across the continent, available information on native bees is spotty at best . 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.
In the following study, we have taken the first step to identify the native bees diversity and abundance in North Georgia Apple Orchards. We have investigated bee abundance and diversity in four North Georgia apple orchards during the entire 2011 growing season. It is believed that native bees can supplement or even replace the honeybee in apple pollination in Georgia.
- 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. Free, J.B., 1993. Insect pollination of crops, 2nd edition. Harcourt Brace Jovanovich, London, United Kingdom. Morse R.A. and N.W. Calderone. 2000. Bee Culture 128:1-15. USDA National Agricultural Statistics Service. 1977. 1076 Honey production report. United States Department of Agriculture. Washington, DC. USDA National Agricultural Statistics Service. 2006. 2005 Honey production report. United States Department of Agriculture. Washington, DC. Johnson, R. 2007. Recent honeybee declines. CRS Report to Congress. Oldroyd, B.P. 2007. What’s killing American honeybees? PLOS Biology 5:1195-1199. Cox-Foster, D.L. S.C. Edward, C. Holmes, G. Palacios, J.D. Evans, N.A. Moran, P. Quan, T. Briese, M. Hornig, D.M. Geiser, V. Martinson, D. vanEngelsdorp, A.L. Kalkstein, A. Drysdale, J. Hui, J.Zhai, L. Cui, S.K. Hutchison, J.F. Simons, M. Egholm, J.S. Pettis, W. I. Lipkin. 2007. A metagenomic survey of microbes in honeybee colony collapse disorder. Sciencexpress. Published online: 6 Sept. 2007 [10.1126/science.1146498]. Michener, C.D. 2007. The bees of the world.2nd. Edition. John Hopkins University Press. Baltimore, MD. 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. 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. Losey J.E., and M. Vaughan. 2006. The economic value of ecological services provided by insects. Bioscience 56:311-323. Isaacs, R. and A.K. Kirk. 2010. Pollination services provided to small scale and large highbush blueberry fields by wild and managed bees. Journal of Applied Ecology. 47(4):841-849. Winfree, R., N.M. Williams, J. Dushoff, and C. Kremen. 2007. Native bees provide insurance against ongoing honeybee losses. Ecology Letters 10(11):1105-1113. National Academy of Sciences. 2007. Status of Pollinators in North America. National Academies Press. Washington, DC.
The study had two main objectives.
(1) The first objective was to conduct a survey of the native bees present in North Georgia Apple Orchards from March to September 2011, in order to measure native bee species diversity and abundance before, during, and after the apple bloom.
(2) The second objective was to measure the success of native bees in apple pollination and fruit production.
Objective 1 – Survey of Native Bees in Georgia Apple Orchards
Native bees were collected using several types of insect collecting traps. These traps included: pan traps, vane traps, and malaise traps. Insect diversity and abundance was measured 2 weeks before the bloom, weekly during the bloom, and once a month after the bloom. During collection days, the traps were set up in the morning and remained up until dusk, which yielded 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)
Objective 2 – Measuring the Success of Native Bees in Apple Pollination
In the following experiment, ten apple trees were randomly selected. In each selected tree, branches of the tree were enclosed with small mesh netting 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, (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). At each orchard, we set up ten experimental trees.
The project had two main objectives: (1) to identify the native bees present in or near North Georgia apple orchards, and (2) to measure the pollination success of the native bees.
Objective 1- To identify the native bees present in or near North Georgia apple orchards throughout the year.
During the 2011 growing season (March- October 2011), 3352 bees were collected. For the bees, 868 were collected from Hillside Orchard, 364 were collected from Mercier Orchard, 1596 were collected from Mountain View Orchard, and 524 were collected from Tiger Mountain Orchard. Included in these numbers are 520 honey bees (Apis mellifera L.). Honeybees accounted for 15.5% of the collection, while native bees accounted for 84.5% of the collection. The bees collected in the 2011 season are listed Table 1.
Mountain View Orchard had the largest number of native bees. At this orchard 96% of the bees collected were native bees. Hillside Orchard had the largest numbers of honey bees. Hillside Orchards maintain a large number of permanent honey bee colonies located on the farm used in honey production for its country store. In this orchard 40% of the bees collected were honeybees (344 honey bees compared with 524 native bees).
There were 82 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), Bombus (Bumble Bees), genera in the Tribe Augochlorini (Green Sweat bees). Hillside Orchard and Mountain View Orchard had the most species diverse collections.
The different groups of native wasps are presented below in Table 2. The native wasps are shown because they were observed landing on the apple flowers, and some wasps are known to drink the flower nectar. There were 505 native wasps collected in the apple orchards. For the wasps, 74 were collected from Hillside Orchard, 32 were collected from Mercier Orchard, 205 were collected from Mountain View Orchard, and 194 were collected from Tiger Mountain Orchard.
Objective 2 – Measuring the Success of Native Bees in Apple Pollination
This year, we had mixed results on a preliminary measurement of the success of native bees in apple pollination. Due to unusually severe weather, including tornados and strong winds in the orchard area of North Georgia, most of our netting enclosures, as well as numerous apple trees in the orchards, were damaged and/or destroyed. Only one enclosure in the Mountain View Orchard remained perfectly intact. In this enclosure, native bees were successful in pollinating the apple blooms. These branches produced a total of 18 apples, which was similar to un-netted branches on the same tree. There were 16 bees captured in the pan traps in the enclosure: 4 Andrena (Melandrena) carlini, 5 Andrena forbseii, 1 Andrena illicis, 5 damaged Andrena (Trachandrena) species, and 1 Lasioglossum (Dialictus) imitatum. Based on this limited study, bees in the Andrenidae family (mining bees) are likely to be the most important native pollinator in North Georgia Apple Orchards.
Tentatively, it can be stated that native bees are capable of fully pollinating the apple trees. Honeybees may not be needed for commercial apple agriculture if an adequate number of native bees are present.
Educational & Outreach Activities
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.
The 2011 study found that most Georgia apple orchards have diverse and abundant sources of native bees. Over 3300 native bees were collected at 4 North Georgia apple orchards in the 2011 growing season. To date, over 100 native bee species have been identified in Georgia Apple orchards by the researchers.
This study has identified the target native bee(s) for apple pollination in North Georgia as Andrena crataegi and Andrena (Melandrena).
The limited netting experiment showed that native bees are capable of pollinating apple flowers and producing large size apples in the same frequency as apple trees pollinated by a combination of honeybees and native bees. It can be concluded that native bees have the potential to replace or supplement honeybees in apple pollination.
In the Unites States alone, honeybees contribute $14.6 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 (Johnson 2007).
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.
During the 2012 growing season, the farmer cooperator at the Mountain View Orchard 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: (1) reducing grass mowing of the orchard (allows wildflowers to supplement native bee food sources), (2) allow the placement of artificial breeding/nesting habitats, and (3) reducing pesticide use. This farmer currently does not bring in honeybee colonies for additional pollination services. However, several honeybee hives (3-4 hives) are adjacent to the orchard. These hives are maintained by a non-professional beekeeper (hobbyist).
Areas needing additional study
The limited netting experiment showed that native bees are capable of pollinating apple flowers and producing large size apples, in the same frequency as apple trees pollinated by a combination of honeybees and native bees. It can be concluded that native bees have the potential to replace honeybees in apple pollination.
In the next growing season, a more detailed netting experiment will be required in order to assess the efficiency of native bees to fully pollinate apples in Georgia’s apple orchards. Special attention will be given to the numbers and size of apples produced by the native bees as compared with honeybees.