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Huanglongbing is a growing threat to California’s citrus industry

A symptom of HLB in citrus is the yellowing of leaves on an individual limb or in one sector of a tree's canopy. (Photo: Citrus Pest and Disease Prevention Program)
Huanglongbing (HLB) is a devastating bacterial disease of citrus that is starting to spread rapidly in urban areas of Southern California. The disease is spread by the invasive insect Asian citrus psyllid.

Asian citrus psyllid was first identified in California in 2008, and has been found from San Diego and Imperial counties in the south, all the way to Sacramento County in the north. See a map of Asian citrus psyllid and huanglongbing distribution in California.

UC Agriculture and Natural Resources specialists and advisors are working with the citrus industry, USDA and CDFA to control ACP populations and keep HLB contained while researchers search for a cure for the disease.

In order to find and remove infected trees before ACP can spread the disease to other trees, UC scientists are focusing research on early HLB detection technologies (EDTs). When infections first start, the bacteria are in just a few leaves. If the sampler doesn't collect those leaves, the disease can be missed. It can take one to two years for the bacteria to distribute itself throughout the tree so this sampling error doesn't occur. 

Early detection technologies use whole tree responses to early infections. For example, Carolyn Slupsky, food science and technology professor at UC Davis, measures changes in tree metabolism (its day-to-day chemical function) when it becomes infected. Every leaf on the tree is connected to the tree's metabolism, so it doesn't matter which leaf is collected. This type of test can detect an infected tree within weeks or months after infection instead of years. 

Scientists are also studying ways to modify ACP so the insects are unable to spread HLB, and studying the use of conventional breeding, genome editing or genetic engineering to develop disease-resistant citrus. Read summaries of the research here.

Young Asian citrus psyllids, called nymphs, produce a white, waxy substance.
Keeping Asian citrus psyllid and huanglongbing disease at bay depends in large part on the active involvement of commercial citrus growers and California residents who have citrus trees in their home landscapes. The UC ANR Asian Citrus Psyllid Distribution and Management website provides detailed guidelines for growers and residents to monitor for Asian citrus psyllid and huanglongbing, and learn about options for reducing psyllid populations and responding to the disease if it's in your area.

View a four-minute video that shows how to monitor for ACP presence in residential citrus:



Posted on Friday, May 31, 2019 at 2:21 PM
Focus Area Tags: Pest Management

UC ANR research to determine future climate change impacts today

Scientific evidence of a warming climate in California and across the globe is clear, but the impacts on ecosystems and agriculture are still difficult to predict.

Sophisticated computer models are used to forecast future climate. Understanding that temperature and precipitation levels will change in the future does not tell the full story: UC Agriculture and Natural Resources researchers also want real-world experience under those future conditions.

Moreover, some agricultural operations have higher sensitivity to the changes than others. Rangeland forage is particularly sensitive to climate changes since, unlike irrigated agriculture, ranchers rely solely on precipitation. They have no control over how much and when it rains.

“It's tricky business,” said rangeland expert Jeremy James, the director of the UC Sierra Foothill Research and Extension Center in Browns Valley. “It's not easy to forecast. We have to address the uncertainty in a realistic manner.”

SFREC director Jeremy James stands next to a small chamber designed to simulate effects of warming air and soil temperatures on rangeland grasses. The poly carbonate hexagons slow rates of heat loss from plots, allowing scientists to artificially warm plants and soils in the chambers. (Photo: Linda Forbes)

Discovering climate change impact on rangeland

In order to study different climate projections on rangeland, James and Maggi Kelly, director of the UC ANR Informatics and Global Information Systems special program, have begun development of a research site that will allow scientists to manipulate the temperature and rainfall on sections of rangeland to understand what would happen under predicted weather scenarios.

The new research facility is currently under construction. (Photo: Linda Forbes)
With a $220,000 National Science Foundation grant, construction is now underway on a four-acre site at the research center that will help scientists learn how temperature and precipitation will impact growth and diversity of forage that ranchers use to raise their livestock.

“We need to know how rangelands will respond when conditions change,” James said. “Will we grow more, but dry out earlier? Will we have more medusahead (an undesirable rangeland weed) or more soft chess (a high quality forage)?”

When complete, 16 shelters on steel tracks will be connected to computer systems and hydraulic motors to move them up or down a research plot. The shelters and other equipment will allow scientists to precisely control the amount of precipitation (or irrigation water) that rains onto the plot. Other systems will give researchers control of air temperature.

“This facility isn't designed for one type of research,” James said. “It is designed to conduct a wide variety of research by scientists over the next several decades. With this setup, we can look at the effect of climate change on soil biological communities, soil carbon, insect communities, plant-insect interactions and oak seedling recruitment.”

The research results from the project should provide ranchers and land managers a better understanding of how climate change may impact agriculture and ecosystem function on rangeland while also providing important information on how to minimize impacts of these changes.

Some aspects of the research facility's development are not covered with funding from the National Science Foundation. The scientists are looking for additional support to complete the project.

For more information, contact James at jjjames@ucanr.edu

The Sierra Foothill Research and Extension Center is one of nine centers across the state of California UC Agriculture and Natural Resources manages for applied research.

Current work underway at the Sierra Foothill Research and Extension Center

The Sierra Foothill REC, a 5,000-acre facility on the Yuba River, has supported research, education and outreach in the Sierra foothills since 1960. Multiple lines of research are being conducted at SFREC. During a recent workshop, scientists from UC Davis, UC Berkeley and UC Cooperative Extension shared a sampling of their work at SFREC.

UCCE livestock and natural resources advisor Dan Macon described a project aimed at helping ranchers make decisions about maintaining a cattle herd when faced with impending drought. Ranchers are reluctant to sell off their cattle even when the near future weather forecast is dire.

“Science tells us you shouldn't feed your way out of a drought,” Macon said. “But you want everything to stay the same. You want to maintain your genetic potential and keep cows that are familiar with the area.”

Working with ranchers, the research project will compare management practices to determine the best way forward when the future looks meteorologically bleak.

“We're assigning cows to a traditional weaning and early weaning groups,” Macon said. “They'll be out on the range from March to early September under different parameters. We're also tying in economics, the value of genetic potential and the value of having cows who know the landscape.”

UCCE advisor Dan Macon, far left with cap, speaks to participants at the workshop.

Research by University of Oregon post doctorate researcher Ashley Shaw is looking into whether compost applied to rangeland will help mitigate climate change by sequestering more carbon, and also benefit forage under drought by increasing the soil's water-holding capacity and improving nutrient delivery.

Preliminary results are promising. A single application of 1/4-inch of compost resulted in forage production that was higher than areas where no amendment was applied and areas that were treated with a chemical fertilizer.

“The biggest impact was under drought shelters,” said Shaw, referring to PVC frames that were covered with plastic during rain events to understand the impact of the treatment under dry conditions. “In the drought plots, the areas where compost was applied are staying green longer.”

A defining research tool at SFREC is a dataset that includes information on monthly rainfall and forage production going back 40 years.

A review of the data shows surprising variations and correlations at the center, where forage production averages 3,000 pounds per acre, but ranges from about 1,000 pounds per acre in 1987, to over 5,000 pounds per acre in 2018, when there was so much growth, “we didn't have enough animals to graze,” James said.

The dataset paints a spectrum of the variation that ranchers across the state must navigate to manage their livestock and rangeland in a way that is profitable and ecologically sound. Research at the Sierra Foothill REC offers invaluable information to help them better understand the ecosystem and make informed decisions.

Posted on Tuesday, May 28, 2019 at 8:36 AM
Focus Area Tags: Agriculture Environment

UCCE lunchtime webinars to be offered during Invasive Species Action Week, June 3-7

When insects, animals, weeds and disease-causing microbes make their way into California from other parts of the nation or the world, the economic and environmental impacts can be catastrophic.

A recent UN report that details the world's biodiversity crisis assigns part of the blame to the proliferation of invasive alien species. “The numbers,” the report says, “have risen by about 70%, across the 21 countries with detailed records” since the 1970s.

“It's time to better understand how invasive species affect California's biodiversity, as well as our water supply, fire regimes, recreation and agriculture,” said Sabrina Drill, UC Cooperative Extension natural resources advisor in Los Angeles and Ventura counties. Drill worked with the California Invasive Plant Council and the California Department of Fish and Wildlife to offer five free 40-minute mid-day webinars on invasive species as part of the multi-agency sponsored California Invasive Species Action Week.

During the first part of the week the series cover a range of organisms, from killer algae and incestuous beetles to rodents of unusual size. Later in the week, it's Weeds-A-Palooza, with talks focusing on invasive plants.

The webinars will be offered using Zoom Video Communications from 12:10 to 12:50 p.m June 3-7. All details are available online at https://ucanr.edu/sites/invasivelunch/invasivelunch2019/. Links to the Zoom meeting space will be posted on that webpage before the webinars begin.

In 2008, zebra mussels were found in San Justo Reservoir in central California and have not been observed in any other water body in California, Nevada or Oregon. (Photo: U.S. Fish and Wildlife)
Monday, June 3: “How they get here: Aquatic invasive species being moved around the world”

Sabrina Drill, UCCE natural resources advisor, and Edwin Grosholz, Department of Environmental Science and Policy, UC Davis 
Most people only hear about an invasive species when they are here causing problems. But preventing new invasive species from getting here in the first place requires understanding the “pathways” of introduction. From tsunamis to aquariums, container ships to canoes, Grosholz and Drill will discuss ways that freshwater and marine organisms travel to California, and how we can prevent spreading them once they arrive.

Tuesday, June 4: “What's killing California's trees? Shot hole borers, palm weevils and the rest”

Beatriz Nobua-Behrmann, urban forestry and natural resources advisor, UC Cooperative Extension in Orange County
Tree pests come to Golden State from around the world and threaten street trees, agriculture, and natural areas. Last year the legislature in Sacramento allocated $5 million to begin addressing the latest threat – shot hole borers that kill a wide variety of trees in Southern California. Nobua-Behrmann will describe how these insects damage trees and what we can do about it.

Nutria, native to South America, have been found in Central California near permanent water sources, such as rivers, streams, lakes, ponds and wetlands.
Wednesday, June 5: “Rodents of unusual size: Nutria in the Delta”

Valerie Cook-Fletcher, Nutria Eradication Incident Commander, California Department of Fish and Wildlife
Nutria, a South American rodent, have caused extensive damage in Louisiana wetlands for decades. Now nutria have been found in the Sacramento-San Joaquin River Delta and its tributaries and state agencies are working to find them before they can breed and spread. Cook-Fletcher will provide an update on efforts to locate this elusive swimmer in the maze of sloughs and backwaters of California's San Joaquin Valley.

Thursday, June 6: “Citizen stewardship: Tackling giant reed in Contra Costa County”

Mike Anciaux and Bob Simmons, Walnut Creek Watershed Council
Giant reed (Arundo donax) is one of the most damaging wildland weeds in California. More than $20 million was spent to remove it from the Santa Ana River watershed in Southern California to protect the endangered Least Bell's Vireo, a songbird that nests in native streamside vegetation. On the eastern side of San Francisco Bay, citizens are uniting to find and remove hundreds of populations along Contra Costa County's creeks.

Japanese knotweed. (Photo: National Park Service)
Friday, June 7: “Organizing to stop one of the world's worst weeds: Marin Knotweed Task Force”

Eric Wrubel, San Francisco Bay Area Network, National Park Service
Invasive knotweed species are some of the worst weeds in the world. They have become notorious for destroying property values in Europe. Knotweed is extremely difficult to get rid of because its underground rhizomes store energy and resist herbicides. Wrubel will describe the partnership that has formed to eradicate recently found invasive knotweed in the San Geronimo Valley and Lagunitas Creek watersheds in Marin County before it can spread.

Posted on Monday, May 20, 2019 at 8:56 AM
Focus Area Tags: Pest Management

UCCE advisor is tracking down answers to a lettuce aphid mystery

When Alejandro Del Pozo-Valdivia started his new job as UC Cooperative Extension entomology advisor in the Salinas Valley last year, he immediately faced an urgent problem in organic lettuce production.

Pest control advisers were finding lettuce aphids in plants that were supposed to be resistant.

Because lettuce aphids crawl deep within the heart of the lettuce head, and because organic growers do not have many options for chemical pest control, the industry relies on patented lettuce varieties that have been conventionally bred to be unpalatable to the pest.

Alejandro Del Pozo-Valdivia, UC Cooperative Extension entomology advisor in Monterey, Santa Cruz and San Benito counties, in an iceberg lettuce field in Chualar, Calif.

“With other types of aphids, they stay on the outer leaves. When you harvest and clean the head, you are taking the aphids out,” Del Pozo-Valdivia said. “But with the lettuce aphid, it's almost impossible to remove them. We don't want consumers to buy a lettuce with these tiny red insects inside.”

Organic producers pay a premium for resistant seeds to grow lettuce without the lettuce aphid and are mystified by the sudden appearance of the pest inside lettuce heads. Has the aphid developed the capability to feed on resistant varieties? Is there a different lettuce aphid biotype in the area? Since Del Pozo-Valdivia is an entomologist, he is focusing on the pest.

With funding from the California Leafy Green Research Board, Del Pozo-Valdivia and his co-principal investigator, USDA scientist Jim McCreight, have launched a research project to collect and identify the lettuce aphids that are feeding and reproducing in the resistant lettuce in the Salinas Valley.

“I'm asking growers and PCAs to contact me if they find any red aphids in resistant lettuce so we can confirm the type of aphid,” Del Pozo-Valdivia said. “

Comparison between a healthy lettuce plant (right) vs. aphid-infested lettuce (left). Plants were grown inside a greenhouse to sustain a lettuce aphid colony during 2018. (Photo: A. Del Pozo-Valdivia)

Seed companies that hold the patent on resistant lettuce also experienced broken resistance in Europe a few years ago, Del Pozo-Valdivia said. They found that the pest in Europe was a different biotype and are already working on identifying genes to maintain the lettuce aphid resistance.

“We haven't seen any scientific report for the U.S. That's why we decided to take the lead. To take the bull by the horns and identify the aphids here in the Salinas Valley,” Del Pozo-Valdivia said.

The lettuce aphid, Nasonovia ribisnigri. A distinct feature of this aphid is the presence of black stripes at the abdomen of the adults. This species is one of the most difficult aphids to manage in lettuce; since colonies are formed inside (inner leaves) of the lettuce head. (Photo: A. Del Pozo-Valdivia)
Posted on Friday, May 17, 2019 at 8:55 AM
Focus Area Tags: Pest Management

UCCE advisor Rachael Long receives prestigious award

UCCE advisor Rachael Long (Photo: Evett Kilmartin)
Rachael Long, UC Cooperative Extension advisor covering integrated pest management for field crops in Yolo, Solano and Sacramento counties, is the recipient of the 2019 Bradford Rominger Agricultural Sustainability Leadership Award.

Long will receive the award at a presentation at 4:30 p.m. May 28 in the Alpha Gamma Rho Hall (AGR) room of the Walter A. Buehler Alumni Center. A reception begins at 4.

The award, established in 2008, honors individuals who have a broad understanding of agricultural systems and the environment, takes the long view, and aims high to make a difference in the world. Awardees exhibit the leadership, work ethic and integrity epitomized by the late Eric Bradford, a livestock geneticist who served UC Davis for 50 years, and the late Charlie Rominger, a fifth-generation Yolo County farmer and land preservationist.

The award presentation prefaces the Agricultural Sustainability Institute's Distinguished Speakers' Seminar, “Building a Better World, the Opportunity to Achieve Climate Drawdown and a Safe Future" by environmental scientist Jonathan Foley, executive director of Drawdown.  Foley, ranked by Thomas Reuters as among the top 1 percent of the most cited global scientists, will address the audience from 5 to 6 p.m.

Long received her bachelor's degree in biology from UC Berkeley and her master's degree in entomology from UC Davis. She was hired as one of the first sustainable agriculture advisors with UCCE in 1992, with a charge to, “Develop, evaluate, and implement nonchemical approaches to pest management in field crop production that maintains environmental and economic viability of agriculture."

During her career with UCCE, Rachael was a pioneer in developing practices to protect water quality from agricultural crop production, helping farmers meet state mandates for clean surface water. She worked on hedgerows, documenting that field edge plantings of native California plants attract beneficial insects, including bees and natural enemies, for better pest control and pollination in adjacent crops. She documented that birds and bats are farmer allies; they help control codling moth pests in walnut orchards. She's promoted hawks and barn owls for control of rodent pests. She has also written numerous publications focusing on agronomic practices for managing pest, weeds, and diseases in field crop production.

At the time she started her research projects over 25 years ago, her ideas were way outside the box and on the fringe. Now her work is mainstream with the UC IPM guidelines incorporating the value of habitat planting for enhancing natural enemies and pollinators on farms for better pollination and biocontrol of crop pests. The California Healthy Soils Initiative and Natural Resource Conservation Service have cost share funding for hedgerow establishment on farms, for pest management and carbon sequestration. She continues to do research on hedgerows, but more importantly, she strives to be a leader by teaching others about agriculture and the need to have co-existence between farming, food production, and wildlife conservation for a better world for all. Her work is documented in many peer-reviewed publications, UC ANR blogs, cost studies and crop production manuals.

“I'm honored to receive this award, especially in recognition of two extraordinary people, Charlie and Eric," Long said. "I owe thanks to so many people who helped in this journey and feel lucky to work in a community that is open to new ideas. I'm especially grateful to farmers in the Sacramento Valley who allowed me to work on their farms. I couldn't have done all this work without their support.”

Posted on Friday, May 17, 2019 at 8:34 AM
Tags: Rachael Long (12)
Focus Area Tags: Agriculture Pest Management

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