Based on historical data, a new invertebrate species establishes itself in California about every six weeks, on average. They don't all become serious pest problems, but many evade eradication efforts, disrupt carefully balanced integrated pest management programs, hijack sensitive ecosystems, and spoil valued recreational resources and urban landscapes.
UC Agriculture and Natural Resources joins the California Department of Fish and Wildlife and the California Invasive Species Council in marking California Invasive Species Action Week, June 1-9, to raise public awareness of invasive species issues and promote public participation in the fight against California invasive species.
The UC Integrated Pest Management Program and the Center for Invasive Species Research are two UC ANR programs that monitor invasive species and coordinate responses when they become established in the state. They work closely with UC ANR advisors and specialists on eradication, management and prevention of these threats.
|Asian citrus psyllid and huanglongbing
Huanglongbing disease, which kills citrus trees, is spreading in Southern California residential areas and threatening commercial citrus production. There is currently no cure for the huanglongbing disease. It is spread by the Asian citrus psyllid. The insect, a native of Pakistan, Afghanistan and other Asian regions, was first detected in California in 2008. Currently the only way to control the disease is to reduce the psyllid population and to remove trees that are infected or located near the infected trees. Everywhere ACP is found, the pests find and spread HLB. In California, an aggressive push to keep psyllid populations low, regulations to limit the spread of psyllids when trucking the fruit, and active scouting for and removal of HLB-infected trees in residential areas could buy time for researchers to find a solution before California suffers the fate of Florida citrus growers, whose orange production has dropped 70% lower than 20 years ago. More info: ACP/HLB distribution and management
|Brown marmorated stink bug
The first reproducing population of brown marmorated stink bug was found in Los Angeles County in 2006. In 2013, a large population was detected in a midtown Sacramento. A pest of agricultural crops and a serious residential problem, it is a strong flier and also travels long distances by hitching rides in vehicles or inside furniture or other articles when they are moved, often in late summer and early fall. As a result, new infestations pop up in neighborhoods where people travel from infested areas. A native of China, Japan and Korea, BMSB was first documented in the United States in Pennsylvania in 2001. It is either established or found occasionally in about 41 states. More info: Pests in Gardens and Landscapes - Brown marmorated stink bug
South American palm weevilThe South American palm weevil is a destructive pest in its native and invaded ranges. Scientists first found it in San Diego in 2011. As the weevils feed, they drill through the heart of the palm, eventually choking off the fronds and killing the tree. UC ANR is studying the South American palm weevil's biology and life cycle, and trying to find out how they got to California. Traps for monitoring the pest have been developed and deployed. More info: South American palm weevil invasion in San Diego County
Polyphagus shot hole borerThe insect, originally from Asia, was first identified in California in 2012. Shot hole borers bore through bark carrying with them harmful fungus. The fungus attacks the tree's vascular tissue, choking off water, causing branch dieback and eventually killing the tree. Polyphagous shot hole borer and the fungus are now distributed widely in more than 110 types of trees in Los Angeles and Orange counties, and have been observed in San Bernardino, Riverside and San Diego counties. More info: Invasive shot hole borers
Sudden oak deathSudden oak death is caused by the pathogen Phytophthora ramorum, which was inadvertently introduced to California forests on nursery stock in the 1990s. The disease has killed up to 50 million trees (primarily tanoak, coast live oak, California black oak, Shreve's oak and canyon live oak) from Big Sur to southwest Oregon. More info: http://www.suddenoakdeath.org
Dyer's woadDyer's woad is an invasive weed thought to have been introduced into California in the Scott Valley of Siskiyou County, where it is locally referred to as "Marlahan mustard." Until a couple of decades ago, it was primarily confined to Scott Valley, but it has subsequently spilled over into Shasta Valley. It continues to spread throughout Siskiyou County and into Modoc, Shasta and other northern California counties. During medieval times, Dyer's woad was one of the most valuable plant commodities in Europe, cultivated as a source of blue dye as early as the 13th century. Colonists first introduced it to the eastern United States for that purpose. UC ANR researchers are developing management practices for removing Dyer's woad and using solarization to kill the seeds in the field, limiting the risk of seed being spread when dead weeds are removed for disposal. More info: UC IPM Pest Note on Dyer's Woad
Yellow starthistleYellow starthistle is native to Eurasia and was introduced to California around 1850 via South America. Recent reports indicate that yellow starthistle infests between 10 and 15 million acres in California. It is common in open areas on roadsides, rangeland, wildlands, hay fields and pastures. Disturbances created by cultivation, poorly timed mowing, road building and maintenance, or overgrazing favor this rapid colonizer. It forms dense infestations and rapidly depletes soil moisture, preventing the establishment of other species. It is also poisonous to horses, causing a nervous disorder called “chewing disease,” which is fatal once symptoms develop. Horses are the only animal known to be affected in this manner and should not be allowed to graze on yellow starthistle. More info: UC IPM Pest Note on yellow starthistle
SaltcedarSaltcedar is native to Eurasia and was introduced into California through the nursery industry. The weed is tolerant of high salinity. Saltcedar's dry branches and leaves can increase fire frequency. After fires, saltcedar sprouts rigorously, while native trees and shrubs generally do not, enabling saltcedar groves to push out native species. Research shows that saltcedar could impact the structure and dynamics of streams by trapping and stabilizing sediments, increasing overbank flooding following high flow events and creating permanent sand bars in rivers. This pest also contributes to the decline of wetland communities as habitat refuge for wildlife. More info: Center for Invasive Species Research
Arundo donaxArundo donax is native to the Mediterranean and tropical Asia. In California from the late 1700s to early 1800s, giant reed was often planted for erosion control in flood channels and as wind breaks. The bamboo-like perennial can grow to 25 feet tall with thick, well-developed rhizomes. It develops dense stands that displace native vegetation, diminish wildlife habitat, increase flooding and siltation in natural areas and create a wildfire hazard. More info: Arundo donax
Japanese dodderThere are several species of dodder native to California, but they are not as difficult to manage as Japanese dodder, which was identified in Shasta and Yuba counties in 2005. This invasive plant pest has thick stems that resemble spaghetti. It grows larger and faster than native dodders and can cover entire trees or shrubs. In California, no viable seeds have been observed following Japanese dodder flowering. Instead, most spread occurs through the dissemination of small pieces of stems distributed by birds and other animals or through pruning, composting, and the improper disposal of infested plant material. This weed is has spread to more than a dozen California counties including Alameda, Butte, Contra Costa, Fresno, Los Angeles, Merced, Sacramento, Shasta, Solano, Sutter, Tulare, Yolo, and Yuba. Contact your county agricultural commissioner to receive proper identification and help with control. More info: UC IPM
Find more information on the UC Integrated Pest Management Program Invasive and Exotic Pests website: https://www2.ipm.ucanr.edu/Invasive-and-Exotic-Pests/
At an invasive species summit last year in Sacramento, UC ANR vice president Glenda Humiston and California Department of Food and Agriculture secretary Karen Ross convened scientists, government representatives and volunteers to pool intellectual resources and plot a strategy for protecting agricultural crops, natural resources, cityscapes and residential neighborhoods from invasive species.
“We know that collectively, we have the tools and expertise to prevent invasive species from entering California, spreading and becoming established,” Humiston said.
Below are three examples of pests that entered California, and with research, collaboration and treatment, were eradicated from the state.
European grapevine moth
European grapevine moth, a native of Mediterranean Europe, was detected for the first time in the Americas in Chile in April 2008. The following year, European grapevine moth was found in California's iconic wine region, Napa Valley. From there it spread to nine other California counties, as far south as Fresno. UC ANR academics responded rapidly — working with public and private partners and international scientists — to develop a pest management program that relied on deploying pheromone dispensers to disrupt mating and application of carefully timed insecticides. UC ANR academics studied the moth's biology, life cycle, host range and proven management practices. In short order, the moth population plummeted, and eventually the state was declared free of European grapevine moth, lifting a quarantine, enhancing farmers' ability to export their agricultural products, and preserving the communities' economic wellbeing. More info: Growers, scientists and regulators collaborate on European grapevine moth program
Pink bollworm of cottonIt took 50 years, but the invasive pink bollworm of cotton was declared eradicated in California in 2018. Eradication of pink bollworm was a joint effort by UC Cooperative Extension, USDA's Agricultural Research Service, county agricultural commissioners' offices and California cotton growers. It involved the implementation of integrated pest management techniques, such as planting transgenic cotton, using insect pheromones to disrupt mating, releasing sterile insects to slow reproduction, plowing after each crop to provide host-free periods, and extensive surveying. California cotton growers funded the program by paying an assessment on cotton grown in the state. More info: Pink bollworm UC Pest Management Guidelines
Red palm weevilIn August 2010, arborists removed a dying Canary Island date palm from the yard of a Laguna Beach home and reported finding large black and red striped beetles. The pests were confirmed to be the first record of the destructive red palm weevil in the U.S. Hormone monitoring and visual surveys of other palms in the area confirmed the presence of the pest. Rapid action was taken against the pest by applying pesticides to trees that showed feeding damage to palm fronds. Effective surveying was accomplished by combining hormone attractants and cut pieces of palm trees provided by the California date palm industry. The last live weevil was detected in Laguna in January 2012. After three years passed with no weevil detections in Laguna Beach, USDA-APHIS declared this pest to be officially eradicated in January 2015. More info: Red palm weevil successfully eradicated form California
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.
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:
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.”
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.
“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 firstname.lastname@example.org.
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.”
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.
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.
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.
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.
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.