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.
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 . 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 .
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. . 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 . 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  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 . 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 . 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 .
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).
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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.