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Organic farmers are counting on UC to control exotic Virginia creeper leafhoppers

Organic farmers are struggling with invasion of exotic Virginia creeper leafhoppers in Lake and Mendocino counties.
When Virginia creeper leafhopper made its way into Mendocino and Lake county wine country a few years ago, some certified organic winegrape producers threw in the towel.

“They lost too much income,” said Glenn McGourty, a UC Agriculture and Natural Resources Cooperative Extension advisor in Lake and Mendocino counties. “They decided they were not going to risk their crop until there is a workable biological control solution to this new pest.”

Meanwhile, other organic grape producers are hanging on to their organic certification and counting on UC ANR researchers to come through with a biological control option soon.

“Organic farmers are spending a couple hundred dollars per acre for organic pesticides,” McGourty said. “They don't want to use them. It takes out beneficial insects and it doesn't even control Virginia creeper leafhopper very well.”

Three leafhopper species are pests of California grapes. Western grape leafhopper is a native insect that's present throughout California north of the Tehachapi Mountains. Several natural enemies keep the pest in check most years. Variegated leafhopper migrated north from the Imperial Valley to Central California in the 1980s, and is established in Napa Valley and other valleys of Napa County. Virginia creeper leafhopper, a native of the northern Midwest, made its way to Northern California in the early 1980s. It migrated southward to the northern Sacramento Valley and Sierra foothills, and most recently was detected in Lake and Mendocino counties, where the population boomed.

“The farmers were devastated, especially financially,” McGourty said. “Conventional growers had to begin spraying pesticides. Some organic vineyards were completely defoliated.”

The leafhoppers' key natural enemies are fairyflies (Genus: Anagrus), among the tiniest flying insects in the world. Certain species of fairyflies attack certain species of leafhoppers. What has scientists perplexed at the moment is the fact that Virginia creeper leafhoppers' natural enemies are present in Mendocino and Lake counties, but they are failing to do their job.

Generally, fairyflies lay their eggs in leafhopper eggs, killing them. The fairyflies known to attack Virginia creeper leafhopper are successfully parasitizing the pest's eggs in Yolo County. However, the very same species of fairyfly is not recognizing Virginia creeper leafhopper eggs as a host in Mendocino and Lake counties.

Virginia creeper leafhopper adults have a reddish-brown zigzag marking on each front wing.
“Virginia creeper leafhopper only recently moved into the Mendocino area,” said post-doctoral researcher Houston Wilson. Wilson works in the lab of Kent Daane, UC ANR Cooperative Extension specialist based at the UC Kearney Agricultural Research and Extension Center in Parlier. “Although these Anagrus parasitoids can attack both Western grape leafhopper and Virginia creeper leafhopper, the Anagrus population in Mendocino County has been reproducing on Western grape leafhopper for so long, they seem to have lost their preference for Virginia creeper.”

The scientists believe that, in time, fairyflies in Lake and Mendocino counties will begin to parasitize Virginia creeper leafhopper eggs on their own. But, because of the severity of the situation to organic winegrape growers, they've hatched a plan to help out the natural enemies. This summer, they will be rounding up fairyflies in the Davis area – where they know how to attack Virginia creeper – and bring them to Lake and Mendocino county vineyards.

Beginning in April, Wilson will allow Mendocino area Virginia creeper leafhoppers to lay eggs on potted grapevines. The vines will be transported to Davis, where local fairyflies can parasitize the eggs. The plants will go back to the laboratory in Berkeley so scientists can rear populations of the parasitoids and later release them in Mendocino and Lake county vineyards.

“I just planted the grapevines this month,” Wilson said. “When leafhoppers become active in the summer, we'll start monthly releases. We hope our efforts will take some of the pressure off winegrape farmers soon.”

In addition to the work releasing natural enemies of Virginia creeper leafhopper, UC Agriculture and Natural Resources scientists are implementing an area-wide integrated pest management program in Mendocino and Lake counties. The program – a combination of biological, cultural and chemical controls for this pest – employs:

  1. Improved monitoring and mapping of Virginia creeper populations
  2. Cultural practices to reduce egg deposition in vineyards
  3. Earlier and coordinated pesticide applications (if a spray is necessary)

The Virginia creeper leafhopper pest control program is funded in part by the American Vineyard Foundation.

An initiative to manage endemic and invasive pests and diseases is part of UC Agriculture and Natural Resources Strategic Vision 2025.

Author: Jeannette Warnert

Posted on Wednesday, February 25, 2015 at 9:01 AM

Insecticide use threatens onion seed production

A honeybee collects nectar on an onion blossom. (Photo: Kathy Keatley Garvey)
Insecticides farmers use in Northern California onion seed production appear to repel honeybees, which can result in reduced seed yields, according to a recent study by UC Agriculture and Natural Resources (UC ANR) researchers.

Visitation by honeybees is the single most important factor for onion seed set in commercial fields, said Rachael Long, UC ANR Cooperative Extension farm advisor in Yolo County.

“The more honeybees that visited the onion flowers, the higher the seed yield,” Long said.

If insecticides are applied repeatedly prior to onion bloom, honeybees were less likely to visit once the flowers opened up.

“If you spray three times in the spring before onion bloom, there was less honeybee activity during early bloom,” Long said. “We weren't sure why. We didn't see any dead bees. Honeybees might be repelled by the insecticide because, if a spray took place close to bloom, their visitation was significantly reduced, but increased later during bloom, as if the insecticide affects wore off.”

Yolo and Colusa county farmers play an important role in worldwide onion seed production. Many different varieties of onions are grown in the region to produce seed ideal for use on onion farms from Siberia to the equator and every latitude in between.

“Growing high quality onions in different areas around the world requires varieties specially adapted to a wide range of conditions, such as day length,” Long said. “In our region, you'll see a tremendous diversity of onions being grown for seed – some short, some tall, some bloom early, others later. There's also all the red, yellow and white bulb variations.”

George Weiss had been farming in Yolo County for more than 50 years when he noticed a mysterious decline in onion seed production in 2009. He paid a visit to the local UC ANR Cooperative Extension office.

“We grow onions for seed, and we weren't getting the seed yields we thought we should have,” said Weiss, 80.

He spoke with Long, who immediately began collecting information on insecticide use on the Weiss and neighboring farms.

A researcher counts honeybees in a blooming onion field.
“I saw a trend,” Long said. “The more insecticides that were sprayed, the lower the onion seed yield.”

Onion seed companies and officials at the California Garlic and Onion Research Advisory Board also observed lower yields.

“We all noticed a decline in seed production over the years, but we couldn't put a finger on what was happening,” said Bob Ehn, CEO of the California Garlic and Onion Research Advisory Board.

Long, Ehn and UC Davis entomology professor Neal Williams worked together to secure a $250,000 grant from the California Department of Food and Agriculture Specialty Crops Block Grant program to solve the onion seed mystery. Ehn's board also provided funding for research.

The sharp decline in onion seed yields began when growers were dealing with a new disease, iris yellow spot virus. The virus is spread by tiny insects called onion thrips, so growers began applying insecticides in early spring to keep the pests from moving the damaging disease around the field.

Over three years, scientists collected extensive data on insecticide use, honeybee activity, soil moisture, pollen germination, and nectar production on 29 onion seed farms of 25 acres of more. They learned that three applications of insecticide in the spring resulted in less honey bee visitation, which can reduce yield given the importance of honeybees in crop pollination.

The data analysis also concluded that:

  • If farmers sprayed insecticides too close to bloom, there was less pollen germination. Typically, when a bee transfers pollen from the male to female flower, the pollen germinates right away and begins to grow, but less so after insecticide use. “There might be some chemical interaction that prevents pollen from germinating. It's not a huge effect, but there's an impact,” Long said.
  • If the soil was too dry or too wet, nectar production in the onion flowers dropped way off, reducing honeybee activity and seed yields. “Honeybees need rewards,” Long said. “Their visitation to flowers is based on the ability to collect nectar. If there is little to no nectar, they will just bypass the flowers and find another source of nectar.”
  • Fungicide use in onion fields did not impact honeybee activity.
  • Pronounced effects of insecticides on pollinator behavior and seed set are more likely at rates of three sprays per year or more, however, even at reduced insecticide use, the researchers still saw the potential for subtle effects on both the pattern of honeybee visitation over time and the pollen-stigma interactions.

An onion field in full bloom was the site of UC ANR research.
“These results highlight the importance of field management practices on the pollination process. In hybrid onion seed production, we recommend moderation in insecticide use and careful management of water during bloom for maximum nectar production,” Long said.

Ehn said the research furnished valuable information for California onion seed growers.

“We now know we have to be very careful about insecticide management prior to bloom time,” Ehn said. “We have to be more strategic about insecticide planning and avoid it as much as possible.”

Ehn said field research by Long, Williams and other UC ANR Cooperative Extension advisors and specialists is of critical importance to the California Garlic and Onion Research and Advisory Board.

“We are totally dependent on Cooperative Extension,” Ehn said. “Our research with Cooperative Extension stretches from Imperial County up to Tule Lake (on the Oregon border). They are our strength and anchor to get research work done that we set as a priority.”

Weiss said he highly values the research assistance from UC ANR Cooperative Extension.

“I can't pin it down in dollars and cents, but it all goes together with experience,” Weiss said.

An initiative to enhance competitive and sustainable food systems is part of UC Agriculture and Natural Resources Strategic Vision 2025.

Posted on Tuesday, February 24, 2015 at 9:32 AM
Tags: honeybees (2), onion (1), Rachael Long (3)

Future looks bright at UC Ag Field Day

More than 3,500 FFA and 4-H high school students from California and surrounding states will gather on March 6 and 7 at UC Davis for the annual Agricultural and Environmental Sciences Field Day. The smart, passionate youth will compete in two dozen agriculture contests, from livestock judging, to agricultural mechanics, to floriculture, to computer applications, and more.

FFA (formerly known as Future Farmers of America) and 4-H are youth development programs that help prepare young people for careers in the rapidly changing world of agriculture. 4-H, which is offered in California by UC Agriculture and Natural Resources Cooperative Extension, allows members to choose from projects in science, engineering, technology, animal science education, nutrition, healthy living and many other experiential learning activities.

Each year the young competitors spend countless hours preparing for the field day, the largest of its kind in the state.

Meat judging is among the competitions at Ag Field Day.

“Competing in Ag Field Day instilled in me the importance of a strong work ethic, the value of research, and the benefits of scientific methods for solving real-world problems in agriculture,” said Yousef Buzayan, a 2011 Ag Field Day participant now double-majoring in Managerial Economics and International Agricultural Development at UC Davis.

Ag Field Day is run and managed completely by UC Davis students who gain valuable experience in leadership, communication, and teamwork.

“Of all my experiences at UC Davis, managing Ag Field Day was definitely the biggest challenge, and with it came the biggest rewards,” said Mary Kimball, executive director of the Center for Land-Based Learning in Winters, California, who helped organize Ag Field Day as a student in 1992. “I learned how to manage many moving parts, and I learned that the best way to get things done well is to do it as a team.”

So if you're in Davis and see thousands of high school students on campus, you'll know who they are: tomorrow's leaders striving and thriving in Ag Field Day competitions. The future of agriculture is in good hands.​

Thinning is an effective tool for management of blue oak woodlands

Blue oak trees are only found in the coastal and Sierra foothills of California.
Stately oak trees with blue-green leaves – known as blue oaks – are found in the foothills of California's Sierra Nevada and coast range, and nowhere else on earth. They are valued for their beauty, wildlife habitat, shade and acorn production. Protecting the resource poses challenges since the vast majority of blue oak woodlands are part of privately held ranches where owners use the landscape to raise cattle for a living.

Researchers with UC Agriculture and Natural Resources (UC ANR) have worked with landowners for decades to help them manage these oak woodlands in ways that balance the ranchers' economic needs with ecological considerations.

In the late 1990s, Tulare County ranchers Jim and Gay Versteeg were interested in thinning their blue oak stands in order to improve biodiversity of the forage growing on the land. The family offered UC ANR researchers three acres to study blue oak tree management practices to better understand the impacts of various thinning practices.

For thousands of years, fire was an important part of California's oak woodlands. Native Americans and, more recently, ranchers set fires to improve habitat and enhance desirable vegetation. However, aggressive fire exclusion during the last 30 years has led to significantly denser stands of blue oak trees.

“We looked into the fire history on the Versteeg ranch,” said Richard Standiford, UC ANR Cooperative Extension specialist based at UC Berkeley. “It burned about every 13 years prior to 1965, but since then, there have been no fires at all.”

Standiford conducted the study with two San Joaquin Valley-based Cooperative Extension natural resources advisors, Neil McDougald of Fresno and Madera counties and Ralph Phillips of Kern County. One-third of the study area was moderately thinned, and one-third was heavily thinned. For comparison purposes, the researchers left one-third of the study area untouched. The study area excluded livestock, but it was accessible to deer and rodents.

Blue oak trees regenerate after thinning.
Over a period of 11 years, acorn production, stump sprouts, forage composition and forage yields were evaluated in each study block. Standiford said thinning the stand enhanced forage production, which is favorable for cattle ranchers. In areas with the highest level of thinning, there was the highest level of forage. However, the thinning did not enhance vegetative biodiversity, as the ranchers hoped.

“The Versteegs thought that, with more sunlight, the amount of native grasses would increase, but that wasn't the case,” Standiford said. “The vegetation in all the plots was mostly grasses and forbs that were introduced after Europeans began settling California, as it is in most oak woodland around the state.”

Thinning did result in the growth of younger trees from stump sprouting.

“We want the sprouts to come back to provide the next generation of trees so when the big ones die or blow over, there are young trees to take their places,” Standiford said. “The main way in which blue oaks regenerate is sprouting from stumps.”

Acorn production on a landscape scale was not impacted by thinning. Trees in the thinned plots produced more acorns per tree, however, because there were fewer trees, the same amount of acorns per acre was produced.

Standiford shared the results of the study with ranchers, land managers and researchers at the 7th California Oak Symposium in 2014; the research will be published in the symposium proceedings later this spring. He said the study results validate for landowners that thinning is an appropriate management practice on blue oak rangeland. Forage increases, the trees survive and grow back.

“If ranchers intend to thin every 15 years or so, moderate thinning is acceptable,” Standiford said. “If this is something they would do every 30 years, they could thin heavily.”

An initiative to maintain and enhance sustainable natural ecosystems is part of UC Agriculture and Natural Resources Strategic Vision 2025.

Posted on Friday, February 20, 2015 at 8:39 AM

Conservation ag may allow farmers to be part of carbon ‘cap and trade’

No-till cover crop seeding into cotton and tomato residues.
Long-term research by UC Agriculture and Natural Resources scientists has documented the capacity for farmland in the San Joaquin Valley managed with conservation practices to sequester carbon, results that could give farmers a seat at the carbon trading table. The study was published this month in the Agronomy Journal.

Published research results provide evidence that farmers will need to get credit for sequestering carbon if such an opportunity arises in the future. In addition, the conservation practices have been shown to offer other environmental benefits – such as reducing dust emissions and cutting water use – while increasing yield and profit.

Initiated in 1999 at the UC West Side Research and Extension Center, the study is a tomato-cotton rotation grown in four treatments: 1) standard tillage, 2) standard tillage and a winter cover crop, 3) no till and no cover crops, 4) no till and a winter cover crop.

“It took about eight years until we saw an increase in carbon in the top foot of soil,” said the lead author Jeff Mitchell, a UC ANR Cooperative Extension specialist. Mitchell is working with UC Davis soil scientists Randy Southard, Will Horwath and Kate Scow, UC ANR Cooperative Extension advisors in Fresno County Dan Munk, Kurt Hembree and Tom Turini, and USDA Natural Resources Conservation Service partners Dennis Chessman and Rob Roy.

Standard tillage is the way most annual crops are managed in the San Joaquin Valley today. The soil is tilled to break up organic matter and reshape beds each year after the crop is harvested. Under no-till management, the plants are left after harvest and the new crop is planted amidst the untouched dead plant residue.

Higher soil carbon was found in plots where cover crops were planted in the winter and the soil was not tilled
Most years the researchers planted a cover crop mixture that included triticale, rye and peas in November. Around the beginning of March, the cover crop was chopped and disked in on the standard till plots. It was chopped and left on the surface in no-till.

The hike in soil carbon was found in plots where cover crops were planted in the winter and the soil was not tilled. Carbon in the soil rose from the standard baseline levels for this region in California, about 8.8 tons per acre, to 12.9 tons per acre, an increase of about 4.2 tons.

“That is a significant increase in carbon,” Mitchell said.

Carbon sequestration is part of the process of carbon cycling around the earth. Atmospheric carbon – carbon dioxide – is taken up by plants in the process of photosynthesis. The plant respires some of the carbon; the rest is converted into sugars and makes up the structure of the plants' stems, leaves and fruit.

In time, the plant dies, decomposes and the carbon that was part of the body of the plant remains in the soil. Micro-organisms convert the carbon into more stable forms of carbon, like humus.

“This more stable form of carbon in the soil is what contributes to soil organic matter and carbon sequestration in the soil,” Mitchell said. “The soil becomes a carbon sink.”

A benefit of storing carbon in the soil is reducing the amount of carbon in the atmosphere.

“We're reducing the atmospheric load of carbon dioxide, a greenhouse gas that plays an important role in global warming,” Mitchell said. “Proving a stable storage location for carbon could allow agriculture to be part of future cap and trade programs.”

An initiative to maintain and enhance sustainable natural ecosystems is part of UC Agriculture and Natural Resources Strategic Vision 2025.

Posted on Tuesday, February 17, 2015 at 8:42 AM

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