UC Berkeley Urban Bee Lab - The Buzz, Volume 12, September 2016
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Trap Nesting
As part of our 'Farming for Native Bees' project in Contra Costa and Ventura Counties, we've installed and monitored diverse floral habitat on several small farms with the goal of attracting native bees to the sites. Developing this habitat has seemed to be a reliable way to build and maintain these populations over time, which is particularly notable for farmers because wild bees can supplement the pollination services of managed honey bees.

An understudied area of this work is nesting habitat for cavity-nesting bees. Roughly 30% of wild bees, including some of the most important crop pollinators, use cavities for nesting. Recommendations for creating 'bee condos' and 'bee hotels' abound, and we know that bees and other insects will use them, but fewer specifics are known about nesting. As part of her undergraduate senior thesis, Chiara Galassetti '17 has undertaken the work of figuring out some of these details. She writes: 

"As a UC Berkeley undergraduate volunteering in the Urban Bee Lab, I’ve always been intrigued by the trap nests implemented in our experimental bee garden on campus and in local farms in Contra Costa County. While an array of factors are contributing to the decline of our native bees, it’s thought that these trap nests may be part of helping counteract this phenomenon by providing additional spaces for cavity-nesting native bees to lay their eggs. However, when checking these trap nests, we often found that parasitic insects like wasps and spiders were living inside, instead of bees. This sparked my interest. Are manmade cavity nests actually providing shelter for bees or are they just housing other insects? To what extent is this true? I decided to do some research. To my surprise, hardly any scientific studies on trap nesting were conducted, and none were conducted in California agricultural settings. 

            As my senior year came around and I started thinking of thesis project ideas for my degree program in Environmental Science, I began discussing the potential of a trap nesting study with Dr. Frankie. We both became excited over the idea of placing trap nests around our farm sites to gather exploratory data on different variables. With the help of the other undergraduates in the lab, I started drilling and cutting wood for trap nests. I contacted five local farms to get approval to conduct my experiment in their orchards.  It was decided that we would be dissecting the nests to determine the ratio of bees to parasites nested. We also created differently-sized nesting holes, to see if that affected nesting rates. The trap nests were placed into the farms in late May and will be removed in October. We are now going out to the farms periodically to collect data and check on the nests. Hopefully when our data is collected and organized we can shed some more light on the effectiveness of creating additional nesting habitat, and ultimately help combat the decline of our native pollinators." 
-Chris Jadallah and Chiara Galassetti 

Featured Event: "Native Bees in Your Backyard" on September 17th in Hopland, CA.

How can you encourage your garden to be buzzing with life? Dr. Gordon Frankie and Dr. Rollin Coville, along with award-winning gardener and author of “The Bee-Friendly Garden”, Kate Frey, will come together for this workshop to discover more about our native bees and other pollinators.

The morning will be spent learning about some of the 1,600 native bee species found in California, from the leafcutting bee to the cuckoo bee, the sweat bee to the mining bee! How can we identify them and how can we accommodate their needs in our gardens? Dr. Frankie will share the research done by UC Berkeley’s Urban Bee Lab and Dr. Coville shares his incredible photographs of native bees in action!

After a locally sourced lunch from Black Dog Farm catering, we will carpool to the gardens of Kate Frey (approximately 5 miles from HREC, and 1 minute off Hwy 101 in Hopland). Kate’s gardens are renowned for their floristic diversity, color and the habitats they provide for wildlife.

This is a rare opportunity not to be missed, tickets are limited and registration is required. Details here. Can't make it? Consider coming to hear Gordon and Kate speak at the Cornerstone Gardens in Sonoma on October 2nd. Details below in 'Upcoming Events' section. 

Above: Images of Kate Frey's beautiful wildlife-friendly garden in Hopland, California. For more photos and information, visit 
Upcoming Events:
September 17: Native Bees in your Backyard Workshop. Details above. 
September 25 - 30: Gordon will be at the Entomological Society of America's XXV International Congress of Entomology in Orlando, FL. 

October 2: Gordon and Kate are speaking at the Cornerstone Garden in Sonoma. Find details for registration here

October 23: We will be at the Friends of Sausal Creek Fall Plant Sale in Oakland. Details TBA on website. 

Interested in bringing us to an event? Fill out a presentation request form here
Featured CA Bee:

 Ceratina spp.

Our Lab has been particularly interested in Ceratina spp. because of their role in crop pollination. Frequency counts have revealed them visiting the crop flowers of several target species, berries being a significant one. 

These small, rather hairless, shiny bees range in color from black to a metallic dark green. There are 350 species within the Ceratina genus worldwide, with 13 being found in California. Ceratina nanula and Ceratina acantha are two of the most common. Fun fact: Some populations of Ceratina acantha in Southern California consist only of females- they are able to reproduce asexually! 

They can often be found nesting in the hollowed-out pithy stems of woody perennials. Deadheading and cutting back shrubs like Salvia mellifera and Perovskia atriplicifolia creates ideal nesting habitat for them. They are generalists, meaning they’ll visit many flowers for pollen and nectar, with some favorites being in the Aster, Erigeron, and Nepeta genera.

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