The highbush blueberry (V. australe Small and V. corymbosum L.) is the major cultivated species of blueberry in North America. A good commercial blueberry crop requires that at least 80 percent of the blossoms set fruit. Blueberry flowers are characterized as being an entomophilous flower, which is defined as a flower adapted for insect pollination. Three types of bees account for nearly all of the pollination of blueberry flowers; bumblebees (Bombus spp.), honeybees (Apis mellifera L.) and solitary bees (Osmia spp.). Due to cost and maintenance issues of honey bee colonies, other pollinator species for blueberry pollination needs to be evaluated.
Four pollinator treatments were evaluated; hornedfaced bee (Osmia cornifrons Radoszkowski), honey bees, natural pollinators, and no pollinators to determine if use of the hornedfaced bee will successfully pollinate blueberry blooms and produce an increased fruit set and a higher quality berry as compared to the other pollinator treatments. Hornfaced bees were not significantly different with respect to berry number, berry weight and weight per berry from the commercial bumble bee and the honey bee. The key difference was the population numbers of each treatment. Hornfaced bees per tent were approximately 30, commercial bumble bees per tent were approximately 75 and the honey bees per tent were approximately 10,000. This Preliminary data suggests that hornfaced bees are as or more efficient than other tested pollinators in this project.
Ericaceae are mostly shrubs comprising about 125 genera and 3,500 species which include several members that have economic importance for ornamentals and edibles in the U.S. Ornamental members include the genus Rhododendron (azalea and rhododendron) and edible members include the genus Vaccinium (cranberry and blueberry). Blueberry plants are cultivated primarily for their berries which can be eaten fresh or processed. Blueberry consumption has an added health benefit which has increased their market demand. Researchers at the USDA Human Nutrition Center (HNRCA) have found that blueberries have the highest antioxidant activity when compared to 40 other fresh fruits and vegetables (Wang et al., 1996). Antioxidants help neutralize harmful by-products of metabolism called “free radicals” that can lead to cancer and other age related diseases (Prior et al., 1998). Anthocyanin, a plant pigment that makes the blueberries blue is thought to be responsible for this major health benefit. Three distinct types of blueberry: rabbiteye (V. ashei Reade), lowbush (V. angustifolium Ait. and V. myrtilloides Michx.) and highbush (V. australe Small and V. corymbosum L.).
The highbush blueberry is the major cultivated species of blueberry in North America (NRAES, 1992). A good commercial blueberry crop requires that at least 80 percent of the blossoms set fruit (Merrill, 1936). Blueberry flowers are characterized as being an entomophilous flower, which is defined as a flower adapted for insect pollination and includes traits such as fragrant, pollen that is not wind-borne, and nectar producing (Eck, 1988). An entomophilous flower discourages self-pollination and encourages cross-pollination.
Three types of bees account for nearly all of the pollination of blueberry flowers; bumblebees (Bombus spp.), honeybees (Apis mellifera L.) and solitary bees (Osmia spp.)(Eck, 1988). Eck (1988) states that bumblebees are excellent pollinators but are not very prevalent during blueberry bloom and where land is intensively cultivated and suggests that colonies of honeybees are essential to insure adequate blossom pollination. Native bees have shown to interfere with blueberry pollination including a species of bumblebee (Bombus occidentalis Greene) and a species of carpenter bee (Xylocopa virinica L.)(Maloof, 2001; Sampson et al., 2004). Both of these species will cut slits at the base of the flower to reach the nectar, bypassing flower reproductive parts, thus they do not assist in pollination and has been termed as nectar robbery. Nectar robbery can have significant effects on reducing pollination of blueberry flowers due to the overlapping of foraging times of honeybees and carpenter bees. Sampson et al (2004) states that honeybee workers do not actively gather blueberry pollen and have a stronger predilection for gleaning nectar from robbery slits reducing their effectiveness as pollinators. Solitary bees are often considered to be pollen bees. Pollen bees gather pollen and honey to make bee bread used to feed their brood. Solitary female bees will mate, makes a nest with about 10 brood cells, stocks each cell with a nectar and pollen mixture as food for her larvae, lays an egg in each, and dies before her young emerge (Batra, 1994). Batra (1994) states that approximately 85% of all bees are pollen bees but due to intensive and extensive cultivation, urbanization and pesticide use, natural populations have declined in many areas resulting in the need for introduced colonies of honeybees for successful pollination.
The first species of pollen bee to be brought into management was the hornedfaced bee (Osmia cornifrons Radoszkowski) which was introduced in the U.S. from Japan in 1977 (Batra, 1994). Batra (1994) gives 10 reasons for the rapidly increasing popularity of hornfaced bees and their close relatives for pollination which are: 1. these bees are active in the spring, before honeybee colonies reach large sizes; 2. they prefer fruit flowers, thus stay in the crop; 3. they usually contact the flowers’ anthers and stigmas on every visit; 4. they fly rapidly, thus working many flowers; 5. the pollen is carried loosely under the abdomen, thus being freely dusted on the stigmas; 6. males also pollinate; 7. their short flight range keeps them in the orchard; 8. growers can easily raise their own bees; 9. they are gentle, with a mild sting; and 10. they can be stored away between pollination seasons. Another important aspect of the hornedfaced bee is that as few as 80 female bees are needed per hectare of apples which contrast with the thousands of bees recommended per hectare for pollination of an orchard (Batra, 1994). Mites and diseases that trouble honey bees do don infest hornedfaced bees and they cannot interbreed with Africanized “killer” honeybees. Research has been conducted on different plant spp. (Brassica spp., Sinapis alba, Helianthus petiolaris) comparing the horned faced bee with honeybees to determine pollination efficacy within controlled field cages (Abel et al., 2003; Wilson et al. 2000). Wilson et al. (1999) stated that using honeybees as compared to hornedfaced bees in field-cage pollinations of Brassicaceae, there was a seven-fold cost increase making the hornedfaced bees more economical for use as a crop pollinator.
Batra, S. 1994. Diversify with pollen bees. Amer. Bee J. 134(9):591-594.
Eck, P. 1988. Blueberry Science. Rutgers University Press. New Brunswick, NJ
Maloof, J.E. 2001. The effects of a bumble nectar robber on plant reproductive success and pollinator behavior. Amer. J. of Bot. 88(11):1960-1965.
Merrill, T.A. 1936. Pollination of the highbush blueberry. Mich. Agr. Expt. Sta. Tech. Bul. 151.
Natural Resource, Agriculture, and Engineering Service. NRAES-55. Highbush Blueberry Production Guide. 1992.
Prior, R.L., G. Cao, A. Martin, E. Sofic, J. McEwen, C. O’Brien, N. Lischner, M. Ehlenfeldt, W. Kalt, G. Krewer, and C.m. Mainland. (1998). Antioxidant Capacity As Influenced by Total Phenolic and Anthocyanin Content, Maturity, and Variety of Vaccinium Species. J. Agric. Food Chem.46(7):2686 – 2693.
Sampson, B.J., R.G. Danka, and S.J. Stringer. 2004. Nectar robbery by bees Xylocopa virginica and Apis mellifera contributes to the pollination of rabbiteye blueberry. J. Econ. Entomol. 97(3):735-740.
Sanford, M. 1998. Pollination, the Forgotten Agricultural Input. Proceedings of the Florida Agricultural Conference and Trade Show J. Ferguson, et al eds., pp. 45-47
Wang, H., Cao, G. and Prior, R.L. (1996) Total antioxidant capacity of fruits. J. Agric. Food Chem. 44:701-705.
Wilson, R.L., C.A. Abel and R.L. Luhman, 1999. Comparing three bee species for controlled pollination of selected Brassicaceae. J. Iowa Acad. Sci. 106:1-3.
1. To compare the effects on blueberry flower pollination using hornedfaced bee (Osmia cornifrons), honey bees, natural pollinators, and no pollinators treatments at three different locations based on local pollinator population type.
a. West Virginia University Plant and Soil Science Farm – Established honeybee pollination program
b. Commercial Blueberry Farm – Established hornedfaced pollination program.
c. Developing commercial blueberry farm – Relying completely on natural pollinators with no honeybee or hornedfaced pollination programs located within pollination range.
2. To disseminate research information via peer reviewed journal articles, on-farm demonstrations, grower meetings, web-sites and other extension channels.
This research will give new insights in using hornedfaced bees as a pollinator in highbush blueberry production. The hornedfaced bee has been shown to be more economical, more efficient pollinator and easier to manage than honeybee colonies on species other than blueberry. Results from this project will be made available to growers via peer reviewed journal articles, on-farm demonstrations, grower meetings, web-sites and other extension channels which would benefit blueberry growers in the U.S. Northeast region. Submission of materials will be made to ‘The Blueberry Bulletin’ which is published weekly during the growing season by the Rutgers Cooperative Extension of New Jersey. During the first week of August 2005, the West Virginia University, Division of Plant and Soil Sciences Farm hosts an Organic Farm Field Day which includes tours of research projects being conducted on the farm and associated with the farm. This pollinator project would be included in the 2005 Organic Farm Field Day tour and presentations.
Three locations were selected for use in this research project based on the presence of local pollinator population type and production methods. The first site is the West Virginia University, Division of Plant and Soil Sciences Farm located in Morgantown, WV. This farm is USDA certified organic and presently has a planting of several highbush blueberry cultivars present for experimental use. This site also has an established population of honeybees used for onsite research projects and as a pollinator source which would increase the presence of honeybees being included into the natural pollinator population with limited hornedfaced bee presence. The second site is an established berry farm, McConnell Berry Farm owned and operated by Bob and Debby McConnell located in Independence,
WV. Blueberry crop is produced using standard conventional agricultural practices. This farm has plantings of several highbush blueberry cultivars and has an established pollination program involving hornedfaced bees with limited honeybee presence. The third site is a developing berry farm owned by Robert Burdette who would like to become a USDA certified organic farm in the near future located just outside of Morgantown, WV. This farm has plantings of three highbush blueberry cultivars and has no established supplemental pollinator program present with limited to no honeybee or hornedfaced bee presence.
Five pollinator treatments are to be used in this research project which includes: 1. hornedfaced bees; 2. honeybees; 3. bumble bees (McConnell Berry Farm only); 4. natural pollinators; and 5. no pollinators. Enclosed cages are to be constructed around plants on each farm to prevent mixing of pollinator treatments. Each cage will contain a single pollinator treatment except for the natural pollinator treatment which will consist of plants not caged and exposed only to local natural pollinators consisting of different populations at each of the three farms. Most of the research will be conducted on the McConnell Berry Farm where the four pollinator treatments will be replicated three times. Replication of pollinator treatments at the WVU farm and Burdett’s farm will be conducted once due to limitations of size of plantings and cost.
All three farms have highbush blueberry cultivars present and various stages of development. Selected cultivars will consist of using Vaccinium corymbosum ‘Jersey’ at the WVU Division of Plant and Soil Sciences Farm and McConnell Berry Farm while Vaccinium corymbosum ‘Chandler’ at the Burdette farm since there are no plantings of ‘Jersey’ on this farm. Five plants will be used for each pollinator treatment and a minimum of three branches per plant will be sampled. Each sample branch must have 5 fruit buds present for McConnell Berry Farm plants while each sample branch from the plants on the WVU Division of Plant and Soil Sciences Farm and the Burdette farm must have 3 buds present. This difference is due to establishment age of the blueberry crops on the different farms
April 15, 2005
Identify and tag branches that have a minimum of 5 fruiting buds. Bud number will be counted. Frames for field cages and covered. Pollinator treatment will be introduced to field cage.
Count flowers on each tagged branch. Open field (natural) pollinators will be sampled.
Field cages will be removed along with pollinator treatment. Berries count will be taken and tagged branches will be covered with mesh bag to prevent berry predation.
Mesh bags will be temporarily removed and ripe fruit will be picked from each tagged branch. The fruit from each sample will be counted and weighed.
Repeat ripe fruit picking, counting and weighing of each tagged branch.
Repeat ripe fruit picking, counting and weighing of each tagged branch.
If needed, repeat ripe fruit picking, counting and weighing of each tagged branch and discontinue use of mesh bags.
Data was only collected from McConnell Berry Farm because of Japanese Beetle damage at the two other sites. Berry clusters were covered in mesh bags to prevent predation of berries to allow them to ripen for data collection. The mesh size did not prevent the beetles from entering the bags and subsequently destroying the berries. This result was unexpected which prevented data collection from the WVU Organic Farm and Burdette’s farm, both of which are being managed organically.
Berry Number: 10
Berry Weight: 11.88 grams
Weight per Berry: 1.19 grams
Commercial Bumble Bee (Bombus impatiens)
Berry Number: 249
Berry Weight: 246.20 grams
Weight per Berry: 0.99 grams
Honey Bee (Apis mellifera)
Berry Number: 289
Berry Weight: 259.74 grams
Weight per Berry: 1.14 grams
Open (Native and Introduced) Pollinators
Berry Number: 289
Berry Weight: 380.81 grams
Weight per Berry: 1.32 grams
Hornfaced Bee (Osmia cornifrons)
Berry Number: 195
Berry Weight: 223.54 grams
Weight per Berry: 1.15 grams
Weight per berry was highest with the open pollinators treatment which may be due to a cross pollination effect. Studies have shown that larger berry size is positively correlated with cross pollination of the blossoms. Since the open pollination treatment was not tented, the plant used in this treatment had the possibility of being cross pollinated by other varieties present in the field. Also the open pollination treatment had more bees available due to the established presence of hornfaced bees already on the farm. Hornfaced bees were not significantly different with respect to berry number, berry weight and weight per berry from the commercial bumble bee and the honey bee. The key difference was the population numbers of each treatment. Hornfaced bees per tent were approximately 30, commercial bumble bees per tent were approximately 75 and the honey bees per tent were approximately 10,000.
This research is providing new insights in using hornedfaced bees as a pollinator in highbush blueberry production. The hornedfaced bee has been shown to be more economical, more efficient pollinator and easier to manage than honeybee colonies on species other than blueberry.
Preliminary data suggests that hornfaced bees are as or more efficient than other tested pollinators in this project.
Education & Outreach Activities and Participation Summary
American Society for Horticulture Science
Submitted Abstract for Presentation for 2006 Annual Conference.
WV Entomological Society Meeting – January 2006
Presentation given on results from project.
WV Farm Bureau News – 2006
Arcticle submitted which gives summary and results from this project.
WVU Organic Field Day – August 2005
Presentation and field demonstration was given on results from this project to approximately 50 attendees.
Areas needing additional study
This project showed that hornfaced bees were suitable for highbush blueberry pollination but further data is needed to provide information to be able to make recommendations of use to growers. Further studies need to address questions such as; how many hornfaced bees are needed to pollinate an acre of blueberries, do hornfaced bees have blueberry variety preferences, and do blueberry growers want to use hornfaced bees for pollination?