Investigating Artificial Native Bee Habitats as a Means to Boost Native Bee Pollination and Provide an Additional Revenue Source for Farmers
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 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
Based on the preliminary results of the 2015 survey (March-September), 1582 bees from 17 genera were collected during the survey. (Note: not all the bees have been examined) The most common group was Genus Andrena (mining bees). Andrena crataegi continues to be the most common bee species collected in the apple orchard. See Table 2 for more information.
Impacts and Contributions/Outcomes
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.