California backyards from Ukiah to Los Angeles are nourishing hundreds of native bee species, according to a study published in the July-September 2009 issue of the University of California's California Agriculture journal.

Bees serve a critical role in pollinating native flora, crops and backyard plants and flowers. Evidence is mounting that the number of native pollinators, especially bees, are declining globally as human population expands.

A research team led by UC Berkeley entomologist Gordon Frankie counted bees at more than 30 different ornamental plant species in the gardens of seven California cities, and found a rich variety of native bees in addition to numerous nonnative honey bees. Over the three-year period, they conducted about 2,500 3-minute counts. The article is available online at californiaagriculture.ucanr.org.

"During the study period, we identified five bee families and between about 60 and 80 bee species in each city," Frankie says. "We have continued our counts in 2008 and 2009, and the number of new bees identified in each city continues to increase."

The cities studied were Ukiah, Sacramento, Berkeley, Santa Cruz, San Luis Obispo, Santa Barbara and La Cañada Flintridge (in the San Gabriel Mountains of Los Angeles County).

Of about 4,000 known bee species in the United States, about 1,600 have been identified in California. As opposed to better-known honey bees, which are social and live in hives, most native bees in California are solitary and nest in cavities or the ground.

Across the cities studied, specific bee groups were often associated with particular ornamental plants, such as sunflower and leafcutting bees, bog sage and large carpenter bees, and goldenrod and Halictid bees.

Frankie says that planting gardens in urban areas with an eye toward attracting native bees can help support populations of these important pollinators, as well as other species such as birds and butterflies. "Biodiverse home, school and community gardens can provide urban dwellers of all ages with the opportunity to enjoy, learn about and support insect-plant relationships close to home," Frankie says. "In addition, they may even serve as genetic reserves for the pollination of agricultural crops."

The July-September 2009 issue of California Agriculture journal also includes the following peer-reviewed research findings:

• Diaprepes root weevil, a new California pest, will raise costs for Southern California orchard and nursery operators if it becomes established.
• Lenticel rot, a postharvest disease of potatoes, is causing more economic losses in the San Joaquin Valley and is related to Erwinia early dying of potato plants in the field.
• A review of drip irrigation in the San Joaquin Valley finds that it is profitable and could potentially eliminate the need for subsurface drainage-water disposal facilities.
• Economic models can help policymakers plan responses to a foot-and-mouth disease outbreak in livestock.
• Very large hay bales of about 1,300 pounds are more economical to harvest, resulting in hay-market shifts in California's northern intermountain region and the San Joaquin Valley.
• Calculating whole-farm nutrient balances can help dairy operators comply with new environmental regulations to protect water quality.

California Agriculture is the University of California's peer-reviewed journal of research in agricultural, human and natural resources. For a free subscription, go to californiaagriculture.ucop.edu, write to calag@ucop.edu or call (510) 642-2431 x33.