Research Project: Managing and Conserving Diverse Bee Pollinators for Sustainable Crop Production and Wildland Preservation

Location: Pollinating Insect-Biology, Management, Systematics Research

2019 Annual Report

Objectives
Objective 1: Improve the production and management of non-Apis bees such as blue orchard bees, bumble bees, and alfalfa leafcutting bees for crop pollination by increasing knowledge of bee nutritional needs and environmental effects on bee physiology (especially on diapause and overwintering). Sub-objective 1.1: Identify the pollen and nectar requirements for maintaining non-Apis bee fitness, in both native and managed ecosystems. Sub-objective 1.2: Develop a better understanding of the environmental factors that affect diapause in non-Apis bees, and develop methods to improve winter survival. Objective 2: Identify environmental (e.g. poor nutrition) and biological factors associated with bee declines (non-Apis species and the honey bee) and develop methods to diagnose and control non-Apis mortality, such as pollen ball and chalkbrood, that are caused by parasites, pathogens (e.g. Crithidia and viruses of bumble bees), and pesticides. Sub-objective 2.1: For non-Apis bees, develop methods to control pests and diagnose and treat infectious diseases. Sub-objective 2.2: Identify the primary environmental and biological factors that affect managed bee sustainability. Objective 3: Quantify bee forage in relation to floral resources and management practices, such as grazing and improve nesting design and strategies (e.g. using chemical cues to enhance nest location), to maximize bee pollination. Sub-objective 3.1: Improve the reproduction and health of Megachile rotundata (alfalfa leafcutting bee) and native bees by providing non-crop floral resources. Sub-objective 3.2: Improve production systems for managed non-Apis bees. Objective 4: Improve bee taxonomy and curation and identify mechanisms that affect bee diversity to enhance conservation efforts, particularly in relation to fire and climate change. Sub-objective 4.1: Expand the taxonomy and systematics of native bees and develop user-friendly identification keys. Sub-objective 4.2: Evaluate bee biodiversity and improve the knowledge needed to achieve effective bee conservation and stewardship. Sub-objective 4.3: Evaluate the effect of habitat-altering events on bee diversity and abundance, especially the effects of fire. Sub-objective 4.4: Identify climatic factors that define the ranges, phenologies and population persistence of select native bees.

Approach
Bees are vital to agriculture. The commercial production of more than 90 crops is accomplished through bee pollination. The honey bee is the best known crop pollinator, but unfortunately, honey beekeepers have been facing a recent bee health crisis. Although a significant amount of scientific time and effort has been invested into identifying the causes for poor colony health, the issue can be viewed as a more general problem, the declining availability of pollinators for agriculture and ecosystems. In addition to working toward finding solutions to the health issues facing honey bees, we provide another approach: tapping into the pollination potential of the diverse bee fauna of the U.S. This project plan addresses four main Objectives: (1) Improve non-Apis bee production and management systems. (2) Develop methods to control pathogens and parasites and identify environmental stressors for all bees. (3) Understand the foraging and nutritional needs of non-Apis bees. (4) Improve bee systematics and taxonomy and our knowledge of bee diversity. Our overriding goal is to provide agriculture with a tool box of pollinators. To achieve this, we must provide a better understanding of the causes behind pollinator declines, improve pollinator availability, and better understand how bee population size and density affect crop pollination. Of necessity, this requires addressing diseases and parasites, environmental impacts, and human-induced threats such as pesticides and habitat loss. Equally important is wild bee diversity. Wild bees provide free pollination services for agricultural crops, maintain plant reproduction in natural areas, and ensure a pool of future managed pollinators.

Progress Report
This report documents progress for the bridging project 2080-21000-017-00D. Of the more than 20,000 bee species worldwide, only a small fraction of species has been successfully managed to pollinate agricultural crops. ARS scientists at Logan, Utah, continue research to improve production and management of several species of social and solitary bees currently managed in agricultural systems, and to seek novel pollinators to meet pollination needs. ARS scientists at Logan, Utah, performed research on solitary bees, bumble bees, and honey bees that is of relevance to the general public, alfalfa seed producers, almond growers, fruit growers, bumble bee producers, honey bee keepers, tomato producers, and agencies such as: the Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine Program, U.S. Forest Service (USFS), Natural Resources Conservation Service (NRCS), U.S. Fish and Wildlife Service (FWS), Bureau of Land Management (BLM), National Parks Service (NPS), U.S. Geological Services (USGS), and U.S. Environmental Protection Agency (EPA). Consultation and expertise have been provided to private citizens and to non-profit conservation groups such as Xerces Society for Invertebrate Conservation and North American Pollinator Protection Campaign. Through invited participation in meetings and publications, ARS researchers have informed regulatory agencies and agriculture/chemical industries on the biology of native bees and how their risk of exposure to agrichemical products may be potentially greater than honey bees, given major differences in nesting and provisioning behaviors. With increased focus on native bees, ARS scientists in Logan, Utah, actively collaborated in development and design of native bee surveys. For improved non-Apis bee production and management systems, significant progress was accomplished on using Blue Orchard Bees (BOB) in crop production. Using research findings for the management and deployment of BOBs from almonds, new research has been conducted in tart and sweet cherry and pear pollination using BOBs. Bee reproduction (guaranteeing pollinator availability next season) has also been evaluated, and a several fold return on female bees has been achieved. This research finding is significant since it indicates that a sustainable use of BOBs in pollination is achievable, under some management practices of commercial orchards. The impact of crop management practices is being evaluated on bee reproduction and pollination to develop best management practices to ensure crop pollination and production. Bumble bees used for crop pollination are raised year-round in facilities, and populations must be maintained to provide colonies during peak agricultural production seasons. A method for cold storage of mated bumble bee queens would allow producers to better target production peaks and reduce costs associated with year-round production. ARS scientists compared three cold storage strategies for short term cold storage of queens. By fluctuating the temperature of cold storage, mortality was reduced by nearly 50 percent from bees stored at a constant temperature for two months. These results provide promising insights for bumble bee producers when storing bees at cold temperatures. In other fruit crops such as apples, collaborative research with Cornell University has revealed that the greater the diversity (number and phylogeny) of bees, the greater the yield and quality of the fruit production. This research finding supports the need to maintain and encourage nesting and reproduction by many different species of bees near the orchards. Repeated surveys of bumble bee species throughout several regions of the U.S. and solitary bees in the family Megachilidae have been conducted. For bumble bees, research has found that accurate assessments of community structure can be derived from samples of 100 bumble bees in diverse environments and as few as 50 bees in areas with low diversity or where accuracy is not a primary consideration. These results can be implemented by resource managers seeking to assess bumble bee communities. These research results will be communicated with APHIS and the U.S. FWS. Progress was made in Objective 2 on identifying pathogens in different bee species. In the alfalfa leafcutting bees, progress has been made in describing association of a parasitoid wasp (Mellitobia), defining its species identity, and determining its distribution. Research has found that the parasitoid overwinters with the host. This finding is important to alfalfa seed producers that overwinter and then incubate their bees for the next season. Some of these growers have reported complete destruction of their bee stocks by the parasitoid and, as a result, loss of pollination of their crop. New parasites (queen castrating parasitic nematodes) were found in bumble bees that may be important mortality factors in some species. New species of chalkbrood have also been identified in solitary bees and molecular characterization performed. These research results will add to the ability to identify pathogens. For honey bees, bumble bees, and solitary bees, impacts of commonly used organosilicone spray adjuvants (OSS) and pesticides have been assessed. Both honey bees and bumble bees have decreased survivorship when fed organosilicones at low concentration. Additional research with adults has found that the OSS does increase viral titers in individual bees and that gene expression is altered. Fungicides, insecticides, and spray adjuvants were found to disrupt nesting behavior of solitary bees and impact the attraction of parasitoids to the alfalfa leafcutting bee nests. For Objective 3 (understand foraging and nutritional needs of non-Apis bees), the ability to hold adult alfalfa leafcutting bees for short periods of time has been examined. Feeding the bees sugar water allows for increased survival; future research will examine impacts on reproduction and energy stores of the bees. Progress has been made on understanding pollen needs of developing larvae for both ground nesting bees and bumble bees. The development of a new pollen trap has facilitated pollen studies in bumble bees. For ground nesting bees, such as the alkali bee, data indicates that pollen provisions absorb water and are ingested by larvae, accounting for significant weight gain. Research asking how bees choose host plants for leaf material in nesting has been initiated. Novel methods for tracking bee movement have been developed in collaboration with ARS colleagues in Maricopa, Arizona, and can be used over time without killing bees. Marker proteins and dyes are facilitating tracking of bumble bees in greenhouses and are useful for monitoring movement out of and back into greenhouses. For solitary bees like BOB, these dyes do persist on bees and are being used to monitor foraging distance and pollination in commercial orchards. In Objective 4, the number of specimens in the U.S. National Pollinating Insect Collection has increased since 2018 by 35,000 specimens for a total of over 1.69 million specimens and its publicly available database (U.S. National Pollinating Insect Database) increased by 50,000 data entries to a total of 2,164,774 records. Squash bees are specialist pollinators of squash and related plants and are important for crop production. Despite their importance, the phylogenetics and systematics of squash bees and their close relatives was poorly resolved. Using molecular sequence data, ARS researchers and academic collaborators from Pennsylvania and Brazil have created the most comprehensive phylogenetic tree of squash bees and relatives to date. This work allows for identification of these bees and provides a strong framework for future ecological, agricultural, and conservation-related investigations. The bee genus Hesperapis is found only in the U.S. and Mexico and is an important specialist pollinator of specific flowering plant species in natural and agricultural ecosystems. The genus includes 20 described species, but many undescribed species are known. Using molecular DNA sequencing, ARS scientists from Logan, Utah, and collaborators from several institutions, created a new resource to identify the species, updated the known list of species, and identified relationships among them. This has significance for knowledge of bee diversity and conservation in the U.S. and provides insights into how bees select the plants that they pollinate. In collaboration with APHIS and Utah State University, progress is being made on creating an online pictorial key for identification of potentially invasive Megachilidae and Apis species for use by APHIS inspectors and other regulators. The online key also provides access to other stakeholders for bee information and identification. New molecular methods have been developed that can resolve issues associated with bee systematics and that will be of use in bee identification by non-specialists.

Accomplishments
1. Achievement of sustainable reproduction of blue orchard bee in cherry orchards. The blue orchard bee, or mason bee, can be used in commercial pollination of nut and fruit crops. Traditionally the bees have been sourced from trap nests placed in natural ecosystems. ARS researchers in Logan, Utah, have found ways of managing the bees in commercial pollination to achieve sustainable production of the bees to ensure populations for pollinating the crops the next season. The bees can synergistically work with honey bees to give increased fruit set in the orchards. Like honey bees, the mason bees are also impacted by the crop management practices.

2. Bumble bee cold storage investigated. Bumble bees used for crop pollination are raised year-round in facilities and populations must be maintained to provide colonies during peak agricultural production seasons. A method for cold storage of mated bumble bee queens would allow producers to better target production peaks and reduce costs associated with year-round production. ARS scientists in Logan, Utah, compared three cold storage strategies for short-term cold storage of queens. By fluctuating the temperature of cold storage, mortality was reduced by nearly 50 percent from bees stored at a constant temperature for two months. These results provide promising insights for bumble bee producers when storing bees at cold temperatures.

3. Improved fruit yield and quality is achieved by pollination by diverse bees. ARS researchers in Logan, Utah, collaborated with researchers at Cornell University, and found that crop yields in fruit orchards was highest when there were many different species of bees present. A greater phylogenetic diversity in the bees was associated with higher fruit weight. In addition, it was associated with a greater number of seeds, and with less malformation of the fruit. Growers will benefit from efforts to encourage and conserve bee diversity in and near fruit orchards.

4. Exotic Bee Identification Tool aids in detecting invasive bees. A number of non-native bee species have become established in the U.S. within the last decade and some have had negative impacts. Detecting exotic bees at ports of entry is of great importance to prevent further introductions. The ability to distinguish exotic from native bees is challenging because there are an estimated 20,000 species of bees in the world. The majority of the invasive bees in the U.S. belong to the family Megachilidae. ARS researchers in Logan, Utah, have developed an illustrated, interactive, web-based guide to the bee genera of Megachilidae that allows Animal Plant Health Inspection Service (APHIS) inspectors to identify bee genera that are exotic. Because Megachilidae is a major component of the bees found throughout the United States, the guide is also of use for pollination researchers, land managers, and interested naturalists in identifying their native bees.

5. Improved systematics developed for squash bees and its close relatives. Squash bees are specialist pollinators of squash and related plants and are important for crop production. Despite their importance, the phylogenetics and systematics of squash bees and their close relatives has been poorly resolved. Using molecular sequence data, ARS researchers in Logan, Utah, and academic collaborators from Pennsylvania and Brazil, have created the most comprehensive phylogenetic tree of squash bees and relatives to date. This work allows for identification of these bees and provides a strong framework for future ecological, agricultural, and conservation-related investigations.

6. New methods developed to identify bees that specialize on specific composite flowers. The bee genus Hesperapis is found only in the U.S. and Mexico and is an important specialist pollinator of specific flowering plant species in natural and agricultural ecosystems. The genus includes 20 described species, but many undescribed species are known. Using molecular DNA sequencing, ARS scientists from Logan, Utah, and collaborators from several institutions, created a new resource to identify the species, updated the known list of species, and identified relationships among them. This has significance for knowledge of bee diversity and conservation in the U.S. and provides insights into how bees select the plants that they pollinate.

Review Publications
Rothman, J.A., Andrikopoulos, C., Cox-Foster, D.L., McFrederick, Q.S. 2018. Floral and foliar source affect the bee nest microbial community. Microbial Ecology. 78(2):506-516. https://doi.org/10.1007/s00248-018-1300-3.
Boyle, N.K., Alix, A., Lehmann, D.M., O'Neill, B., Thompson, H.M., Morandin, L., Singh, R., Abbott, J., Raine, N.E., Cox-Foster, D.L., Pitts-Singer, T., Hiranejos, S., Steeger, T. 2018. Workshop on pesticide exposure assessment paradigm for non-Apis bees: foundation and summaries. Environmental Entomology. 48(1):4-11. https://doi.org/10.1093/ee/nvy103.
Griswold, T.L., Rightmyer, M.G. 2017. A revision of the subgenus Osmia (Diceratosmia), with descriptions of three new species (Hymenoptera, Megachilidae). Zootaxa. 4337(1):1-37. https://doi.org/10.11646/zootaxa.4337.1.1.
Rhoades, P., Griswold, T.L., Waits, L., Bosque-Perez, N.A., Kennedy, C.M., Eigenbrode, S.D. 2017. Sampling technique affects detection of habitat factors influencing wild bee communities. Journal of Insect Conservation. 21(4):703-714. https://doi.org/10.1007/s10841-017-0013-0.
Messinger-Carril, O., Griswold, T.L., Haefner, J., Wilson, J.S. 2018. Wild bees of Grand Stairscase-Escalante National Monument: richness, abundance, and spatio-temporal beta-diversity. PeerJ. 6:e5867. https://doi.org/10.7717/peerj.5867.
Gonzalez, V.H., Griswold, T.L., Engel, M.S. 2018. South American leaf-cutter bees (Genus Megachile) of the subgenera Rhyssomegachile and Zonomegachile, with two new subgenera (Hymenoptera: Megachilidae). American Museum Novitates. 425:1-74. https://doi.org/10.1206/00030090-425.1.1.
Delphia, C.M., Griswold, T.L., Reese, E.G., O'Neill, K., Burkle, L.A. 2019. Checklist of bees (Hymenoptera: Apoidea) from small diversified vegetable farms in southwestern Montana. Biodiversity Data Journal. 7:e300625. https://doi.org/10.3897/BDJ.7.e30062.
Sgolastra, F., Hinarejos, S., Pitts-Singer, T., Joseph, T., Luckmann, J., Raine, N. 2018. Pesticide exposure assessment paradigm for solitary bees. Environmental Entomology. 48(1):22-35. https://doi.org/10.1093/ee/nvy105.
Strange, J.P., Delaney, D.A., Tarpy, D.R., James, R.R. 2017. Novel microsatellite loci reveal high genetic diversity yet low population structure for alfalfa leafcutting bees in North America. Conservation Genetics. 18(3):679-687. https://doi.org/10.1007/s10592-017-0943-9.
Tripodi, A.D., Strange, J.P. 2018. Rarely reported, widely distributed, and unexpectedly diverse: Molecular characterization of mermithid nematodes (Nematoda: Mermithidae) infecting bumble bees (Hymenoptera: Apidae: Bombus) in the USA. Parasitology. 145(12):1558-1563. https://doi.org/10.1017/S0031182018000410.