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Pesticide and Pathogen Screening of the Alternative Pollinator Osmia Cornifrons

Danforth, Bryan
Cornell University
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Our project will focus on two main objectives to investigate the effects of pesticides and pathogens on a wild pollinator species in commercial apple orchards.

First, we will screen pollen provisions collected by female Osmia cornifrons in commercial apple orchards for pesticide residues. We will answer the following questions: (1) Are detectible pesticide residues present in the pollen provisions of Osmia cornifrons (2) Do management practices (i.e. organic, integrated fruit management, or conventional) effect the amount or type of pesticide we detect in pollen provisions (3) Is there evidence of pesticide-related mortality in Osmia nests placed in apple orchards

Our second objective is to screen adult Osmia cornifrons bees for pathogens associated with bee population declines in other species. For this objective we will answer the following questions: (1) Do species of Nosema, a microsporian fungus known to be pathogenic in other bee species, infect O. cornifrons (2) Does the level of Nosema infection vary widely among orchards/sites (3) Is the level of Nosema infection related to aspects of orchard management (e.g., pesticide use, presence/absence of honey bees, etc.) We will use the answers to these questions to create educational materials for orchard growers on the effects of pesticide residues and pathogens on alternative pollinator species. We will involve undergraduate students, graduate students, and extension professionals throughout the duration of the project. Alternative managed pollinators, such as Osmia cornifrons, have the potential to improve both the profitability and sustainability of New York apple orchards. This project will be among the first to extend the analytical and molecular techniques developed to look at the effects of pesticides and pathogens on the health of honey bees to wild, non-Apis bees. We will be the first to screen pollen provisions of Osmia species for pesticides and the first to look for Nosema in Osmia (and other wild bee) populations. This project will produce informational materials on the effect of various pesticides on solitary bees and suggest management plans to minimize risk. Our project will directly benefit apple growers and the over 17,000 people who work in the handling, distribution, marketing, processing and shipping of apples, apple consumers, and the natural environment of New York State. We will involve graduate and undergraduate students in the research, thereby exposing students to the importance of insect pollination in their daily lives. By supporting alternative bee pollinators, we will reduce reliance on imported honey bees. As declining populations of honey bees are reported throughout the eastern US, it is essential that we identify the management practices which have the least detrimental impact on native and wild pollinators.

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Non-Technical Summary:
Declines in honey bee populations across the United States over the past 50 years, and reports of dramatic honey bee losses caused by colony collapse disorder (CCD) over the past 5 years, has raised concerns about the long-term advisability of reliance on a sole, non-native crop pollinator (the honey bee). Alternative crop pollinators exist, including wild, native bees occurring naturally in the vicinity of agricultural production as well as managed, alternative pollinators, such as Osmia (mason bees) and Megachile (leaf-cutter bees). In eastern apple orchards there are over 100 native bee species that are likely contributing substantially to apple pollination. In addition, managed pollinators, such as mason bees are known to be excellent apple pollinators based on studies in the western US, Europe and Japan. Our project will focus on one such managed pollinator, Osmia cornifrons (the horn-faced bee). The horn-faced bee is common in the eastern US and populations can be managed and experimentally manipulated using artificial, trap-nests. We will use trap-nests to study two potential threats to long-term viability of horn-faced bee populations in apple orchards: (1) pesticides and (2) fungal pathogens. We will collect and analyze pollen provision masses from trap-nests of the horn-faced bee using standard analytical methods (gas and liquid chromatography) in order to detect the composition and level of pesticides in provision masses. We will screen broadly for insecticides, herbicides, and fungicides, which are all used heavily in apple orchards in the eastern US. We will also compare the levels of pesticides among orchards and we will focus on the impact of orchard management (conventional, IPM, and organic) on pesticide levels in pollen provision masses. Second, we will screen larval and adult bees for fungal pathogens widely implicated in honey bee and bumble bee population declines: Nosema. We will use standard laboratory techniques (PCR amplification of Nosema DNA and DNA sequencing of PCR products) to detect pathogen levels as well as pathogen identity. These results will help us understand whether fungal pathogens pose a threat to long-term management of mason bees in apple orchards. Finally, we will examine if there is an interaction between pesticide levels and pathogen levels. One might expect such an interaction because pesticides have been shown to depress immune function in a variety of organisms. Our project will be the first to directly measure pesticide levels in pollen provision masses and will be the first to attempt to identify fungal pathogens of managed mason bees. Long-term, sustainable apple production may require that apple growers manage their orchards in ways that support wild bee pollinators, and this project will be first step in identifying the best management practices to achieve this goal.

We will establish wild Osmia cornifrons populations at 12 apple orchards in the area surrounding Ithaca and Geneva. We will select farms with a variety of management practices (organic, integrated pest management, conventional) and honey bee abundances. Data on each farm's management and honey bee abundance has been collected by our lab for previous studies of native bee diversity in apple orchards. After bee foraging activity ends each year we will collect pollen provisions to analyze for pesticide residues and adult bees for DNA extraction and presence of Nosema infection. Pesticide residue screening: Osmia conifrons females over-winter as adults and emerge in early spring to mate. After mating, female bees begin the process of laying eggs and gathering pollen to provision each egg. Female bees are active for approximately six weeks, a period which overlaps with apple bloom so that any pesticides sprayed in apple orchards before, during, and after bloom may be present in pollen provisions. As soon as bee foraging activities finish we will collect a subset of nests from all sites. Pollen provisions will be removed and stored -80C for further analysis. Spray records for the period of bee activity will be provided by growers at each farm and will allow us to select which pesticides to screen. Based on pilot study conducted in May, 2011, we expect this list to include the fungicide captan along with the insecticides indoxacarb, difenoconazole, and abamectin. Multiresidue pesticide analysis will be performed by the Connecticut Agricultural Experiment Station's Department of Analytical Chemistry (USDA-CAES) in New Haven, CT and will include both gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Pathogen screening: Thirty adult bees from each site will be collected throughout the active foraging period and stored for pathogen screening. We will use polymerase chain reaction (PCR) and Sanger sequencing of PCR amplicons to determine if species of the microsporidial fungus Nosema are present in any O. cornifrons adults collected at our sites. PCR primers have been developed for Nosema spp. and a number of studies have successfully used this technique to detect Nosema in other bee species.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens