Bees pollinate all of our fruits, nuts, and vegetables. Honeybees contribute approximately $15 billion in pollination services to U.S. commercial agriculture annually. However, reliance on a single insect species, the honeybee, for the pollination of a huge portion of the human food supply can be dangerous. Indeed, this is especially true considering that honeybees are in decline from Colony Collapse Disorder (CCD), thus putting the global food supply at risk. The best alternative to honeybees is the native bees already present in the local environment. With nearly 3500 species in North America alone, the diversity of different forms, pollen-strategies, and behaviors of native bees provides a wide range of use for agricultural operations. It is estimated that native bees already annually contribute $3 billion to U.S. agriculture.
Each crop and each region in the world has its own characteristic group of native bee pollinators. There is very little data concerning regional make-ups of these native pollinator-guilds, which has led to our reliance on the European honeybees. During the past five years, we have surveyed the native bees in North Georgia. Our studies identify the mining bee, Andrena crataegi, and its close relatives, the Melandrena, as being the ideal native bee(s) for North Georgia Apple production. Other excellent apple pollinating native bees indentified were the Mason Bees (Osmia species), Carpenter Bees (Xylocopa virginica), and Bumble Bees (Bombus species). It is time to move to the next step: to develop habitat enrichments and other strategies to increase the abundance of targeted native bees in commercial apple orchards.
Ideal native bee habitat enrichments should: (1) be easy to construct, (2) be low cost, and (3) ideally have the potential to provide farmers with a supplemental income source. If farmers are able to harvest bee larvae (pupa cocoons), they can sell them to other orchard owners or to the public (e.g. to boost their backyard vegetable garden yields). In the current study, we will investigate a prototype habitat enrichment that meets all three criteria.
The project had 2 main objectives or goals.
The main goal of the study was to evaluate the potential of native bee habitat enrichment to boost native bee abundances of previously identified target bee species, as well as provide farmers with a supplemental income source.
The secondary goal was to continue surveying native bees for a sixth year within the apple orchards, with a focus specifically on the apple bloom periods. Significant weather changes, perhaps due to global warming, have resulted in drastically different growing seasons during the past 5 years. The apple bloom shifted 4-5 weeks earlier during the past 2-3 years, occurring in March. Last year the weather shifted back to the typical bloom in April. Native bees abundance and diversity significantly varied during these blooms. These much earlier apple blooms can impact which native bees are present to pollinated the flowers (e.g. mason bees, Osmia species, are more important during early apple blooms).
MAIN GOAL – Evaluate the potential of native bee habitat enrichments
To achieve the main goal, experiments will be performed at three North Georgia apple orchards. In these orchards, habitat enrichment areas tailored specifically to the target Apple-pollinating native bees will be set up. Two groups of native bees will be targeted: mason bees (Osmia species) and mining bees (Andrena species).
Mason bees such as Osmia georgica and O. Taurus (two species identified with great potential in Georgia apple orchards) require nesting tubes, since they are plant stem cavity nesters in nature. Mining bees such as Andrena crataegi (species with the greatest potential to replace the honeybee) prefer patches of soil in which to dig tunnels for their habitat and a place to brood their young.
After some field experimentation, the following design will be implemented: a series of four bee houses with three soil trenches (12 inches wide X 30 long x 12 inches deep) placed in between each bee house. Each bee house will contain 40 different sized nesting tubes (6mm, 7mm, 8mm diameter).
H–H–H–H (H indicates a bee house, – indicates a trench)
Mountain View and Tiger Mountain Orchards will have four enrichment areas. Mercier Orchard will have two enrichment areas. In addition, half of the enrichment areas will have flowering fruit trees (cherry, pear, etc.). It is hypothesized that flowering fruit trees will lure mason and mining bees to enrichment areas, since no other plants are flowering at this time of year.
Enrichment areas offer mason bees nesting habitat and materials. Mason bees require mud to cap off and separate each cell in their nesting tubes. Excavated soil from trenches will be placed around the base of the bee houses. Enrichment areas with flowering fruit trees also offer an early food source. Based on last year’s preliminary study, Osmia georgica prefer 6 mm tubes and O. Taurus prefer 8 mm tubes. During our 5-year native bee survey, we found more than 10 different Osmia species in Georgia apple orchards. In order to assess the success of the nesting tubes for boosting the abundance of the mason bees, we will examine each individual tube to get an exact count of the Osmia. This type of examination does not hurt or injure bees. Most of these bees will be returned back to their originating orchard. Some larvae will be raised to adulthood in order to identify their species.
Mason bees are also a source of supplemental income for farmers. Excess mason bee cocoons (the pupa inside the nesting tube) can be sold to commercial companies like Crown Bees. These companies resell cocoons to individual gardeners and large commercial orchards or farms that wish to boost mason bee abundances. Each nesting tube will contain numerous cocoons. Our pilot study found that on average, 8 cocoons per nesting tube belonged to an Osmia female. Farmers can decide how many mason bees to keep and how many to sell. Additional wild mason bees can always be lured away from wild habitats by enrichment plots adjacent to a farmer’s orchard.
Enrichment areas offer mining bees nesting habitat. Excavated soil will be placed on one side of the trench to create a hill effect. The larger, bare soil hill is believed to attract mining bees to the enrichment area. Mining bees prefer patches of bare soil in which to dig tunnels for their habitat and a place to brood their young. Enrichment areas with flowering fruit trees also offer an early food source. In order to assess the success of the soil enrichment areas for boosting the abundance of mining bees, we will examine the soil for holes (entrances to the colony). We will excavate some areas of the soil to measure larvae abundance.
SECONDARY GOAL – Survey of Native Bees in Georgia Apple Orchards
To achieve the secondary goal, a survey of native bees will be conducted in four North Georgia Apple Orchards.
In these orchards, native bees will be collected using several types of insect collecting traps and procedures, including pan-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. Approximately, 10-12 collections will be made at each orchard during the growing season.
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. Likewise, 2 malaise traps will be set-up (1 trap in the center and the other trap near the edge of the plot) for each sample day. Active collection methods, such as 1-hour timed sweep netting, will also be performed at each orchard during each sampling day.
After the collection, the bees will be brought back to the GGC laboratory to be counted and identified. Bees will be determined to species, pinned, and mounted in permanent collection boxes. Species will be compared to reference collections at the USGS Bee Inventory and Monitoring Lab.
Main Objective – Habitat Enrichments to boost Native Bee Abundances
Mason Bees (Osmia species) – Habitat Enrichments
A total of thirty-two mason bee nest boxes were used in the study (16 at Mountain View Orchard, 8 at Mercier Orchard, and 8 at Tiger Mountain Orchard). The nesting boxes were divided into 2 groups. On one side of the orchard, floral enrichments (e.g. 2 cherry trees and 2 bushes that bloom before apple trees) were added around the nest boxes, while on the other side of the orchard, the“control group side” no trees or bushes were added around the nest boxes. At each orchard, significant nesting took place in the nest boxes. The floral enhancements did not impact mason bee nesting.
Each nesting box contained 70 nesting tubes (6 mm paper tubes, 7mm paper tubes, 8mm paper tubes, small hollow reeds (>7mm), and large hollow reeds <8mm).
650 Osmia cocoons were successfully produced in the nesting tubes. The highest level of nesting took place in 6 mm tubes (see Table 1). The two most common species nesting in the nest boxes were Osmia georgica and O. taurus. Significant parasitism took place in all orchards.
Mining Bee (Andrena species) – Habitat Enrichments
Four trenches were created at each orchard, in order to boost the abundance of the mining bees (Andrena crataegi) and other mining bee species. Mining bees prefer patches of soil in which to dig tunnels for their habitat and brood their young. Two trenches were placed at opposite sides of the sampling plot in each orchard. On one side of the orchard, floral enrichments (e.g. 2 cherry trees and 2 bushes that bloom before apple trees) were added around the trenches, while on the other side “control group side” no trees or bushes were added around the trenches. At each orchard significant nesting took place in the trenches. Both mining bees and sweat bees were observed to nest in the trenches. Approximately 30-50 nesting holes were observed in each trench.
Nesting frequency was more than double on average in “floral enrichment” trenches compared to the control group trenches without floral resources. Bee nesting increased in the trenches throughout the apple bloom. Nesting in the trenches ended in late May.
Secondary Objective – Native Bee Survey
There were 2410 bees collected in the 2015 survey (March-September). The bees showed a high level of abundance and diversity at each farm. The 2410 bees represented 5 bee families and 17 genera were collected during the survey. The most common group was Genus Andrena (mining bees) and Genus Lasioglossum (sweat bees). The Andrena made up 30% (720 of 2410) of the bees sampled, while the Lasioglossum made up 20% (476 of 2410) of the sample. Andrena crataegi continues to be the most common bee species collected in the apple orchards. This species is particularly useful in Georgia. Our past research indicated that these mining bees pollinate better than honey bees based on (1) time spent at the flower, (2) pollen on their body, and (3) behavior on the flower. At least in Georgia, and perhaps throughout the region, the mining bees (Genus Andrena) are the “apple bees”. See Table 2 for more information.
Educational & Outreach Activities
Schlueter, M.A. 2017. Using Native Bees to Boost Crop Production and Lower Food Cost. Keynote Speaker – Seminar on Science 2017. Kamphaeng Phet Rajabhat University, Kamphaeng Phet, Thailand. July 12, 2017.
Published Abstracts and Presentations at Professional Meetings
Stewart, N.G., and M.A. Schlueter. 2016. Temporal variation in the apple bloom from year-to-year (2010-16) significantly affect diversity and abundance of native bee species in north Georgia. 25th International Congress of Entomology. Orlando, Fl. September 25-30, 2016.
Schlueter, M.A. and N.G. Stewart. 2016. A six-year study of bee (Superfamily Apoidea) diversity and abundance in Georgia apple orchards. 25th International Congress of Entomology. Orlando, Fl. September 25-30, 2016.
Schlueter, P.M. and M.A. Schlueter. 2016. An Assessment of Apple (Malus domestica) Pollination by Native Bees. 2016 Annual Meeting – Association of Southeastern Biologists. Concord, N.C. March 31-April 3, 2016.
Schlueter, M.A. and N.G. Stewart. 2016. A Multi-Year Survey of Bee (Superfamily Apoidea) Diversity and Abundance in Georgia Apple Orchards (2010-2015) 2016 Southeastern Branch Meeting of the Entomological Society of America. Raleigh, N.C. March 13-16, 2016.
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, 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, 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.
This project has taken the first step in developing procedures and methods to increase the abundance of 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 identify and 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. In addition, the results of the current study indicate that it may be possible for farmers to harvest extra native bee larvae (cocoons) for an additional revenue source.
This project had several accomplishments.
The habitat enrichment methods designed to boost native bees in the orchards were both successful. The first method of adding nest boxes to the orchard did increase mason bee (Osmia species) abundance. Over 650 mason bees cocoons with developing bees inside were produced by adding the nest boxes. This may even potentially serve as a source of additional revenue for farmers who could sell the cocoons to wholesalers (e.g. Crown Bees), gardeners, or other commercial farmers who are interested in adding more native bees to their gardens or farms.
The second method using trench habitat enrichments (e.g. exposing naked soil) was also successful in boosting mining bees (Andrena species). Approximately 30-50 nesting holes were observed in each trench. The trench enrichments provided additional nesting habitat for the mining bees, which boosted nesting and increased their numbers.
The 2015 Native Bee Survey in North Georgia apple orchards was also quite successful. There were 2410 bees collected in this year’s survey (March-September). The bees showed a high level of abundance and diversity at each farm. The 2410 bees represented 5 bee families and 17 genera were collected during the survey. See Table 2 for more information.
Native bees can boost the pollination of commercial crops. Habitat enrichments can boost native bees, which in turn will help boost crop pollination and production.