A lack of pollination by honey bees — brought on by increased insecticide use to control onion thrips — was linked to a sharp decrease in yields of California onion seeds, according to research published in the July-September 2011 issue of the University of California’s California Agriculture journal.
“Honey bee visits to onion flowers were negatively correlated with the number of insecticides applied per field and field size,” wrote the study’s authors, Rachael F. Long of UC Cooperative Extension in Yolo County and Lora Morandin of the Department of Environmental Science, Policy and Management at UC Berkeley. “Reduced onion seed yields in recent years could be associated with the increase in insecticide use, which may be repelling or killing honey bees, important pollinators of this crop.”
The research was conducted in May and June 2009, in 13 commercial hybrid onion seed production fields in Yolo and Sacramento counties. At each of six sampling sites per field, the researchers observed the numbers and types of insects visiting onion flowers that were potential pollinators of onions. To assess onion seed yields relative to insect pollinator activity, they collected onion umbels from the sampling sites and counted the seeds to obtain average yield data. Ground mapping was done around each field to determine whether other preferred floral resources were available to honey bees, perhaps luring them away from onion flowers.
Onion thrips were previously of minor importance in onion seed production. However, iris yellow spot virus is a new pathogen for California onions that is vectored by onion thrips, and it can cause significant onion seed yield losses if left unmanaged. The insecticides used by growers at these field sites to control onion thrips included spinosad, spinetoram, methomyl, cypermethrin, lambda-cyhalothrin and sodium tetraborohydrate decahydrate. The number of insecticides applied per field ranged from one to seven, including tank mixes, with all pesticides applied prebloom. The number of bee hives per acre ranged from four to 14, with the exception of one field that had resident hives at 42 per acre.
“This study found that the number of insecticides applied and field size were the strongest predictors of honey bee activity and onion seed yields,” the authors wrote.
Long and Morandin cautioned that to confirm a causal relationship, more information is needed on the specific effects of different classes and rates of insecticides on honey bee activity. In addition, cultivar can play a role in honey bee activity and needs to be further investigated with respect to pesticide use and bee activity.
“Our study suggests that growers should exercise caution when using insecticides, applying them only when needed as opposed to preemptively, to better protect both wild and honey bee pollinators,” the authors wrote. “Also, the negative correlation between field size and honey bee activity suggests that spreading honey bee colonies around onion fields rather than grouping them may increase honey bee activity and pollination in larger fields.”
Onion seed is primarily grown in Colusa County and the Imperial Valley on about 2,000 acres. The value of the seeds is $12 million to growers, according to agricultural commissioner county crop reports, and they generate an additional $40 million in subsequent retail sales.
“While clearly a specialty, small-acreage crop, onion seed production is important to the rural economies in California where onion seed is primarily grown,” Long and Morandin noted.
As noted in the Los Angeles Times, “With rising public interest in where our food comes from — as well as in "green" living — it makes sense that higher education would be eager to attract students who want to tap into the intersection between these two fields.”
Students will focus on the social, economic, and environmental aspects of agriculture and food — from farm to table and beyond. The program is designed to help students obtain a diversity of knowledge and skills, both in the classroom and through personal experiences on and off campus.
Students will take courses in a broad range of disciplines, but will focus in one of three tracks: Agriculture and Ecology, Food and Society, or Economics and Policy.
“This interdisciplinary curriculum will prepare students to become leaders in agriculture and food systems,” said professor Thomas Tomich, the major adviser for the program and director of the Agricultural Sustainability Institute at UC Davis.
The major is new, but UC Davis has been covering the subject in field- and classroom-based interdisciplinary learning opportunities at the Student Farm at UC Davis for more than 35 years, said Mark Van Horn, the Student Farm director who will teach a core course in the major.
“Learning through doing and reflection adds a valuable dimension to students’ education because it helps them see the connections between theory and practice in the real world,” Van Horn said.
“This is an exciting addition to the college that reflects a change in how we think about food and agriculture,” said Neal Van Alfen, dean of the College of Agricultural and Environmental Sciences. “Students will gain a broad perspective of what it takes to put dinner on the table in an era of greater demand and fewer resources.”
For more information:
- Full press release
- UC Davis Student Farm
- UC Davis Agricultural Sustainability Institute
- About the major
Soil erosion threatens our ability to feed ourselves in the future. Current concerns regarding soil erosion include economic vitality, environmental quality and human health.
How can losing a little soil to erosion be such a concern? Soil formation is a very slow process. It takes nature between 300 to 1,000 years to replace soil lost over a 25-year period at a loss rate of 1 mm per year (25 mm is approximately 1 inch)
Erosion reduces the productivity in several ways: Plants are not able to use nutrients as efficiently, seedlings are damaged, rooting depth is decreased, soil’s water-holding capacity is diminished, permeability is decreased, runoff increases and the infiltration rate declines. The loss of healthy soil leads to poor plant growth and lower crop yields.
In the United States we lose an estimated 6.9 billion tons of fertile topsoil to erosion each year. Losses of this size are far from sustainable. In an effort to continue food production, costly fertilizers and amendments are used to compensate for the lost soil. The loss of nutrients alone is estimated to cost U.S. farmers $20 billion a year.
As runoff carries sediment, nutrients, and agricultural chemicals off-site, the economic and environmental costs skyrocket.
The University of California has resources to help reduce the loss of soil through erosion. The free, five-page publication Understanding Soil Erosion of Irrigated Agriculture provides information to help maintain the productivity of land and reduce the enormous costs associated with erosion.
- Impacts of soil erosion
- Types of water erosion
- Indicators of soil erosion
- Soil survey interpretations
- Land capability classification system
- Soil erosion factors
- New soil survey resources
Additional resources, can be found at the UC ANR free publication website.
Yellow starthistle is thought to have been introduced into California from Chile during the Gold Rush. The weed readily took hold in California valleys and foothills, thriving in areas where the soil has been disturbed by animals grazing, road construction and wildland firebreaks. Today, yellow starthistle is a very common sight in vacant lots and fields, along roadsides and trails, in pastures and ranch lands, and in parks, open-space preserves and natural areas.
Capable of growing six feet tall and bearing flowers surrounded by inch-long spines, yellow starthistle reduces land value, prevents access to recreational areas, consumes groundwater and poisons horses. (Yellow starthistle isn't all bad. Beekeepers have found that it can provide an important late-season food source for bees.)
That's where goats can come in. Goats will eat yellow starthistle at all phases of growth, including the mature, spiny stage, when it is not palatable to other browsers and grazers.
"When goats eat yellow starthistle, they open up the canopy and allow sunlight to hit the ground," said Roger Ingram, UC Cooperative Extension natural resources advisor. "That allows other, more beneficial seeds to come up and grow. If you can get other plants growing in there, the competition will choke out yellow starthistle."
Landowners can raise goats themselves and direct them to areas of starthistle infestation with portable fencing, or they can lease the animals exclusively for vegetation control. More information on yellow starthistle management is available from the UC Integrated Pest Management Program.
View the video below for more information on goats' browsing preferences.
California must continually increase its use of renewable fuels to meet mandated reductions in greenhouse gas emissions (GHG). The state's historic Global Warming Solutions Act of 2006 (AB32) requires that alternative fuels displace 6 percent of gasoline and diesel use now, and 9 percent by 2012. The number goes up to 11 percent in 2017 and 26 percent in 2022.
California has been meeting these goals by importing millions of gallons of ethanol: 80 percent of the supply is corn ethanol from the Midwest, 12 percent is sugarcane ethanol from Brazil, and the rest is ethanol from corn grown here. By 2012, demand for ethanol fuel will rise to 1.62 billion gallons per year. If California does not increase its production of corn for ethanol, it will need to import 95 percent of that amount.
In the search for a better alternative, scientists have been investigating conversion of cellulose to ethanol. Technical challenges remain, but cellulose offers a potentially abundant feedstock for biofuels.
One of the plants seen as a possible dedicated biofuel crop in the United States is switchgrass. It is about 40 percent cellulose and grows widely in the Midwest and the South. However, it is not native to California and has not been produced here.
Recent studies by UC Davis scientists are the first ever to report tests of different switchgrass ecotypes in California, - and are published in the current California Agriculture journal.
Scientists evaluated the productivity of the two main ecotypes of switchgrass, lowland and upland, under irrigated conditions across four diverse California ecozones — from Tulelake in the cool north to warm Imperial Valley in the south.
”It is important to know how much biomass can be produced in the state before deciding to pursue cellulosic ethanol," says UC Davis plant scientist Gabriel Pedroso. "California has very diverse climatic regions, which affect the adaptability and productivity of switchgrass.”
Because it is a deep-rooted perennial grass, switchgrass promotes soil conservation. It stores carbon in its root system, and makes efficient use of water by virtue of its C4 photorespiration.
Switchgrass requires an establishment year.
"In the second year of production, the lowland varieties grown in the warm San Joaquín and Imperial valleys yielded up to 17 tons per acre of biomass, roughly double the biomass yields of California rice or maize," Pedroso said.
Because it can be used both as forage and as a biofuel crop, switchgrass may be well suited to California, a state with a large livestock industry and higher ethanol consumption than any other.
While the field trial results are promising, commercial, large-scale conversion processes for cellulose to sugars and fuels are just beginning to be demonstrated.
Cellulose is a complex matrix of smaller sugar molecules and fibrous material in plant cell walls. It is the principal structural component of all plant material, including residues and organic materials in municipal solid waste. If it were possible to efficiently break it down into simple sugars, if would become a productive source of ethanol, and would significantly reduce GHG.