Non Technical Summary
Summary Blueberries are an important crop in the US, worth approximately $797 million annually. The crop is primarily pollinated by honey bees, but it can take 5 to 10 colonies per acre to achieve optimal yields. There is a native, solitary bee species, Osmia ribifloris, that specializes on blueberry-type flowers and has been shown previously to pollinate the crop well. This bee's native range includes California and Oregon, who together account for 40% of the value of the US crop ($320 million). While it has been known that this species could be an excellent blueberry pollinator, it has not yet been put into use on a commercial scale. The first step is to begin propagating a large population in their native habitat. Foothill Bee Ranch has located sites in California, on private property, where the bee thrives and over the past 4 years has built a population of over 10,000 bees. This is enough to begin pollinating on a larger scale, as it has been estimated that 1,000 bees per acre are needed. For this research, we will deploy these bees on a significant scale in a real-world, open field trial, to gather data on bee establishment rate, blueberry yield and pollen species collected by the bee. Foothill Bee Ranch will team with an organic blueberry producer in Stockton, California and with solitary bee experts at USDA-ARS and UC Davis. The study will be conducted in six 1-acre plots with honey bees, paired with six 1-acre plots with honey bees and O. ribifloris. We will measure nesting establishment, reproductive rate, flower visitation rate and blueberry yield. If successful, we will be able to plan for raising more of these bees and scaling up the system to pollinate more acres every year. While blueberry yields are often good, honey bees are not ideally suited, anatomically, for blueberries and have been shown to be vulnerable to biotic and abiotic stresses in the environment. Previous research has shown that pollination can be improved when more than one pollinator species is present in a crop setting. Blueberry growers may be able to improve yields by adding this gentle, native species and reducing their numbers of honey bee hives rented. We believe the time has come to begin working with this species on a larger scale and this project will allow us to take the first steps towards that goal.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
211	1120	1130	100%

Knowledge Area
211 - Insects, Mites, and Other Arthropods Affecting Plants;

Subject Of Investigation
1120 - Blueberry;

Field Of Science
1130 - Entomology and acarology;

Goals / Objectives
Goals:1) Prove the concept that O. ribifloris can be deployed in blueberries, successfully pollinate the crop, and measure the reproduction rate there.2) Measure female nest establishment rate in artificial cavities and test three different nesting materials to find an optimal nesting environment in blueberries.3) Examine the pollen brought back by the bees to determine flower species visited and microorganisms present. Verify that the bees visit blueberry flowers and measure flower handling time.4) Measure yield and quality of blueberries where O. ribifloris were deployed and compare to locations without the bee.5) Measure production of bees propagated in natural habitats and compare to reproduction (number of offspring and sex ratio) in commercial blueberry fields.

Project Methods
Methods The experimental design will be to release the bees in 6, 1-acre plots, each separated from each other by at least 100 feet. There will be 6 untreated 1-acre plots, each paired with one of the O. ribifloris plots, at least 300 feet away from them. This will be a paired, t-test experimental design, with the treatments being (1) honey bee only pollination [control], and (2) honey bee and O. ribifloris pollination [treatment]. In an open field trial such as this, it would be impossible to keep honey bees far enough away from the plots to have an O. ribifloris-only test. However, our trial will be a realistic assessment of how the bees will fare in the presence of honey bees, since we would not expect growers to adopt this practice without having some honey bees present as well. One thousand bees will be released in the center of each one-acre plot when bloom begins. Torchio (1990) recommended 300 nesting females per acre for blueberries. The percentage of females in our propagated bees has averaged 39.5% female. We expect to have some of the bees leave the area and not establish and nest. After releasing ≈395 females, an establishment of 50% of the females will provide nearly 200 nesting females per acre, which should be sufficient in the presence of honey bees. Five nesting stations, with a total of 960 holes, will be available for the females to nest in. Each station will be comprised of a 6-foot t-post with three different nesting cavities available (see below). Nests will be protected from rain and wind by placing them in plastic corrugated boxes. Four plants equidistant from the center of the plot and from each other will be tagged, their buds and flowers counted, and later sampled for total number of fruit, to calculate percent fruit set from flowers present, total weight of fruit, and seeds per fruit. Objective 1: During the pollination and nesting period, bee activity will be measured 3 times per week. 20 randomly selected plants in the one-acre area will be watched for one minute, and the number of O. ribifloris and honey bee visitors will be counted. Each week, at least 4 females per plot will be selected and we will measure the length of time that females take to complete a leaf pulp or nectar/pollen foraging trip. The number of completed nests will also be counted on each visit.When the bees are finished nesting, the nests will be retrieved from the field and stored at appropriate summer developmental temperatures (20 to 30°C). A sample of nests will be opened to count the cells, and the number of males and females in each nest. This will allow us to estimate the total number of offspring produced, even if some of them succumb to pests and pathogens. This can be compared to the number of bees released to measure overall bee reproduction in the trial. In the fall, when the offspring have reached the adult stage inside their cocoons, the cocoons will be carefully removed and any dead, diseased or pest species will be removed. The cocoons will be stored at 4°C for the winter to be ready for the next season. Objective 2: We will measure the actual establishment rate by counting the number of females in the cavities after sunset at each release site. Nesting materials offered will be wood laminate nests with 7.5 mm diameter holes, paper tubes with 7.5 mm diameter holes, and paper tubes with 6 mm diameter holes. Objective 3: Sample nests will be opened during the early, middle and late blooming periods and a sample of pollen in the provisions will be collected and sent to Neal Williams and Rachel Vannette at UC Davis for analysis of pollen and microbes present. The composition of pollen and microbes in the provision will be assessed using microscopy and high-throughput sequencing. These results will be compared to nest samples taken from bees nesting in wild habitats. Objective 4: At first harvest, all the ripe fruit will be picked from each sample plant, counted, and weighed to the nearest gram. A random sample of 30 berries will be weighed, to obtain weight per berry. 10 of these berries will be taken to the lab and dissected, and the seeds per berry counted. This will be repeated with subsequent harvests, following the schedule provided by the grower. Objective 5: In January, nesting blocks will be placed on at least 4 privately owned properties in the Sierra Nevada mountains where O. ribifloris has been found previously. At least 500 cocoons will be placed in release chambers at these sites. The nesting blocks will be retrieved in June, and the number of completed nests and live offspring per nest will be measured. These reproductive rates will be compared to the reproductive rates observed in commercial blueberries.