An Asian citrus psyllid (ACP) sample – confirmed positive for Candidatus Liberibacter asiaticus (CLas) the bacteria that causes Huanglongbing (HLB) – was collected from a commercial citrus grove in the Woodcrest area of Riverside County. Confirmed by Citrus Research Board’s Jerry Dimitman Laboratory, this single adult psyllid is the first CLas-positive ACP found in a commercial citrus grove in California.
While a positive ACP detection in a commercial grove is cause for serious concern, as of today, HLB has not been detected in any California commercial groves. That said, it is more crucial than ever that we stop the disease from spreading by eradicating the Asian citrus psyllid in commercial groves. The cost to manage the Asian citrus psyllid is far less than any potential costs or loss to the industry should HLB take hold throughout our state.
An expansion of the HLB quarantine zone will not be established as a result of the CLas-positive ACP detection and CDFA staff is swiftly conducting surveys and collecting samples per the ACP/HLB Action Plan from the perimeter of all commercial groves and all residential HLB host plants that are located within a 250-meter radius around the find.
While treatment is not mandatory as a result of the detection, all growers within 250-meters of the find site will be notified to apply insecticides to all HLB host material within the designated area with materials recommended by the University of California (UC).
Currently, the best way to stop the disease from spreading is to stop the ACP. To stop the ACP, we must restrict its movement and suppress existing psyllid populations. It is critical to follow best practices and review recommendations from the UC on how to protect commercial citrus groves from HLB. Regulations are in place to help prevent the spread of the pest and disease. All growers, packers and haulers must comply with all California Department of Food and Agriculture, county and federal regulations, including quarantines.
Growers in Riverside County may contact the County Agricultural Commissioner’s office or the CDFA Pest Hotline at 800-491-1899 for additional information. If you see or suspect ACP or HLB symptoms in your grove, please notify the CDFA hotline. – By the Citrus Pest & Disease Prevention Program
To provide industry members, including field crews, with best practices to prevent the spread of the Asian citrus psyllid (ACP) in California’s citrus groves, the Citrus Pest & Disease Prevention Program has developed a mobile-friendly, Spanish-language field crew training video that can be used by field crew supervisors and farm labor contractors prior to harvest.
This video, which stems directly from our in-person train-the-trainer workshops, provides an overview of best practices for field crews to prevent Huanglongbing (HLB) from threatening the California citrus industry’s livelihood and infecting commercial groves.
A direct, downloadable version of this video is available here.
We all must do our part if we’re going to protect California citrus from this disease – and field crews are at the forefront. For additional resources and videos, please visit CitrusInsider.org/Resources.
In 2005, a disease called Huanglongbing (HLB, citrus greening, was identified in Florida’s commercial citrus groves. The disease is caused by a bacterium that affects all citrus cultivars by disrupting the flow of nutrients from the source of production, to the site of use, causing tree decline. HLB weakens the root system, increases early fruit and leaf drop, lowers tree productivity and fruit quality and ultimately kills the tree. The disease has spread to all the major production regions in Florida. Economic losses have exceeded more than $4 billion dollars. Currently, more than 95% of Florida’s trees are infected. There is currently no cure for the disease.
Efforts to control HLB have been unsuccessful as the bacterium cannot be cultured, literally grown, in a petri dish, and once in the plant it proliferates within the citrus phloem. Phloem is the system that transports sugars from their site of production, the leaves, to plant parts that use sugars, the roots or flowers.Phloem transport is generally downward but can be upward as well.
Once the HLB bacterium is in a tree’s phloem it has the potential to infect the entire tree. It is exceedingly difficult to introduce any control agent into the phloem with the conventional control methods of foliar spraying or soil drenching.
Thus far, no treatment preventing HLB infection, or controlling the bacterium once within the tree, has been developed. Potential chemicals are being investigated, but in order to test them, direct or indirect phloem delivery, where the bacterium proliferates, is needed. Therefore, an effective method of delivering an effective volume of theraputics into the phloem is needed to evaluate potential treatments.
What is the focus of this project?
Our project focuses on developing a method of delivering therapeutic liquid materials, bactericides, microbial metabolites, RNAi, or biologicals, into the citrus vascular tissues, both the xylem which conducts water and nutrients upward from the roots and the phloem, which conducts sugars and other metabolic products downward from the leaves. We are investigating diffusion, trunk punctures with a surrounding liquid reservoir for passive uptake and infusion, low pressure active injections. We are focusing on these methods as foliar sprays and root drenches have not been successful phloem delivery methods.
Who will be doing the research?
The project is led by plant pathologist Dr. Ozgur Batuman with colleagues at the Southwest Florida Research and Education Center (SWFREC) at University of Florida in Immokalee. This four-year project will also study the citrus vascular system with a multidisciplinary research team including UF Plant Pathologists Drs. Nabil Killiny and Amit Levy at Lake Alfred, SWFREC UF Plant Physiologist Ute Albrecht, Citrus Horticulturist Fernando Alferez, Precision Ag. Engineer Yiannis Ampatzidis, Agricultural and Natural Resources Economist Tara Wade, University of California-Davis Extension Specialist Louise Ferguson and Texas A&M-Kingsville Citrus Center Plant Pathologist Veronica Ancona as well as number of graduate students, postdocs, and Florida, Texas and California citrus industry members.
How will this research be done?
Our earlier research involving comparisons of delivery methods including foliar sprays, soil drenching and trunk injection determined Needle-Assisted Trunk Infusion (NATI) was the best potential delivery method (Figure.1). In initial experiments, using NATI, 1 ml of rhodamine (1%) dye was injected into the trunks of one-year-old citrus seedlings. A visible red color, indicative of rhodamine uptake and movement, was detected in the upper-most leaves within 30-60 min and an increase in color intensity was observed within 24 hours. Similar results were observed in two-year-old grafted Valencia plants within 48 hours. If the NATI delivery method can be automated, large numbers of trees could be treated quickly. Once the delivery method has been developed, implementation will be tested with potential treatments developed within other research projects.
Our proposed automated delivery would consist of a robotic arm with several modules at the end of the arm, installed on an ATV or tractor. One module with needles would grip and puncture the trunk, a second module would wrap a reservoir around the trunk below the punctures and third module would fill the reservoir. (Figure 2). Hopefully, a robotic arm plus automated system will be inexpensive enough for growers to purchase and simple enough to use.
Another approach is disease prevention; application pf prophylactic chemicals that prevent infection. In this scenario our system would be used treat healthy young trees with bactericides or boost their immune system. When infected by the ACP the bacterium would either be killed or suppressed, perhaps below the level that harms tree growth and productivity. This option is analogous to the vaccinations that prevent diseases in humans and animals.
What are the greatest challenges and opportunities?
The greatest challenge is successful phloem delivery. The greatest opportunity is that, if successful, we will have developed a method that will allow much more precise deliver of theraputics to citrus trees. For example, if an effective phloem delivery method is developed, it could be used to control insects that feed on citrus plant parts. Or, it could be used to deliver growth regulators, perhaps nutrients and carbohydrates, to roots and fruits to increase growth, development and fruit quality; much like an intravenous injection functions in an animal.
Among the questions we hope to investigate are:
When, what kind of, and what amount of therapeutics can be applied by NATI?
At what frequency?
What type of citrus tree: cultivar, age, infected, healthy is the best for treatment by NATI?
Can we kill the bacterium? How and when to assess a change in bacteria titer after treatment?
When will become available and be economically feasible for growers?
— By Ozgur Batuman, Southwest Florida Research and Education Center, University of Florida; and Louise Ferguson, Department of Plant Sciences, University of California Davis
Figure 1. Distribution of rhodamine (red dye; 1%) applied by NATI in various tissues (left) of grafted and non-grafted young citrus plants grown in the greenhouse (right). Photos taken 2 weeks after the treatments. Treatments and tissues observed are indicated. Yo = year-old.Figure 2. Projected automated delivery system (ADS); an ATV with extendable arm with NATI and the cover placement systems on the arm guided onto the tree trunk.
Stakes at All-Time High for Backyard & Commercial Trees in 2019
Detections of Huanglongbing (HLB), an incurable plant disease that kills citrus trees, increased by 160 percent in 2018 compared to the previous year, signaling the growing threat to the state’s iconic citrus trees, landscape and economy.
HLB is spread by a small pest called the Asian citrus psyllid as it feeds on citrus tree leaves. The disease is not dangerous to humans or pets, but it is fatal for citrus trees and has no cure. Once a tree is confirmed with the disease, it must be removed from the property in order to protect neighboring citrus trees.
The disease was first discovered in California in 2012 in Hacienda Heights. HLB was detected in 269 trees in 2017 and 699 trees in 2018, with a majority of these occurring in Los Angeles and Orange counties. The disease has not yet been detected in a California commercial grove.
HLB has devastated commercial citrus production in Florida. Over the course of 10 years, Florida’s commercial citrus industry lost $7.8 billion in revenue, 162,200 citrus acres and more than 7,500 jobs due to HLB. Should the disease spread from backyard trees in Southern California to nearby commercial citrus groves, the livelihood of California’s citrus production could impact about 3,900 farmers and 292,000 acres of citrus production in the state. Commercially grown citrus contributes $7 billion in economic impact to the state and employs more than 22,000 individuals.
“The livelihood of California’s commercial citrus industry and the generations of families it supports is at risk because of HLB,” said Jim Gorden, a citrus grower in the San Joaquin Valley and chair of the Citrus Pest & Disease Prevention Committee. “We are at a crossroads, and we must all work together to do what is necessary to protect our citrus.”
Asian Citrus Psyllid Adults
The California Department of Food and Agriculture (CDFA) has established quarantines throughout the state that limit the transport of citrus across state and international lines, and between areas where the psyllid and disease have been found. Additionally, CDFA has agriculture crews canvasing the state to inspect backyard citrus trees for the Asian citrus psyllid and HLB.
“The Department is committed to our partnership with California’s commercial citrus industry and residential citrus growers to fight HLB,” said Victoria Hornbaker, interim director of the citrus program at CDFA. “With more than half of California residences estimated to have a citrus tree on their property, and California citrus production supporting billions of dollars in our state’s economy, we all play an instrumental role in protecting our citrus.”
California residents play an important role in protecting the state’s citrus trees. Residents should:
Proactively inspect their citrus trees for the Asian citrus psyllid and HLB monthly, and whenever watering, spraying, pruning or tending trees.
Adult Asian citrus psyllids are brown, about one-eighth of an inch long, and feed with their body at a 45-degree angle on citrus leaves.
Symptoms of HLB include blotchy and yellowing leaves, premature and excessive fruit drop, lopsided fruit, and bitter, inedible fruit.
Call the state’s pest hotline at 800-491-1899 if the pest or disease is spotted.
Cooperate with agriculture officials who may ask to inspect or treat their citrus tree.
As part of tree maintenance, visit a local nursery or garden center to get advice on products that can help protect citrus trees.
When pruning citrus trees, be sure to dry out citrus clippings or double bag them before removing the plant material from the property.
Refrain from moving citrus plants, foliage or fruit as doing this may unknowingly spread the pest.
More information and photos of Asian citrus psyllids and HLB symptoms are available at CaliforniaCitrusThreat.org.
Washington, D. C., (April 12, 2018) – Each year, harmful invasive plant pests and diseases cost the United States about $40 billion in crop losses, damage to forests and vulnerable ecosystems, and expensive eradication and control efforts. It only takes one person who moves one piece of infested firewood, one infected plant, or one piece of infested fruit to spread these invasive pests to a new area. That’s why USDA’s Animal and Plant Health Inspection Service (APHIS) has designated April as Invasive Plant Pest and Disease Awareness Month. Spring is the perfect time to remind everyone of the simple steps they can take to prevent the spread of harmful invasive plant pests.
The USDA believes that Huanglongbing (HLB, or citrus greening) was spread from Florida to California by one person who likely mailed an infected plant to that State. HLB was first detected in Florida in 2005 and has since spread rapidly. A concerted effort by USDA, states (including California), and the citrus industry is underway to find new strategies in the fight against HLB.
The good news is that individuals can also stop the spread of invasive pests by looking for and reporting suspicious insects or signs of damage (Report a pest in California). For example, USDA detected Asian longhorned beetle in Boston in 2010 when a single groundskeeper with a keen eye noticed and reported an unusual dime-sized hole in a tree. That one call provided early warning to jumpstart an eradication effort that quickly eliminated this destructive pest from that city.
Here’s what you can do to help keep invasive pests from spreading as spring gets underway and all year round:
Spring is a busy time for buying plants. Buy yours from reputable nurseries or online businesses. Ask if they comply with federal and state quarantine restrictions to ensure their plants are pest-free.
Planning to travel? Whether it’s between states or to another country, check with your local USDA office before you bring back fruits, vegetables or plants so you know what’s allowed. And when returning from abroad, always declare all agricultural items to U.S. Customs and Border Protection so they can make sure items are free of harmful pests or diseases.
When enjoying the great outdoors, don’t move untreated firewood. Instead, buy or responsibly gather firewood near the place you’ll burn it. Or, take certified, heat-treated firewood on your trip with you.
If you live in an area under state or federal quarantine for an invasive pest, don’t move produce or plants off your property. Call your local USDA office to find out how to safely dispose of yard debris like trees and branches. Also, allow authorized agricultural workers access to your property for pest or disease surveys.
Make sure to clean outdoor items before moving them. Wash dirt from outdoor gear and tires before traveling long distances to or from fishing, hunting or camping trips. If relocating to a new home, clean lawn furniture and other outdoor items before placing them in a moving van or storage pod.
To learn more, visit www.HungryPests.com or join the conversation on Facebook or Twitter. The website includes photos and descriptions of 19 invasive pests that can be moved easily by people, an online federal quarantine tracker by state, and phone numbers for reporting signs of invasive pests.
As the CA citrus industry works to fight the HLB disease carrying Asian Citrus Psyllid from destroying the industry, the California Citrus Clonal Protection Program is playing a key role in preparing the industry for battle. Watch this interview with Georgios Vidalakis, Director of the program as he explains. Read more in California Fresh Fruit Magazine.
As the CA citrus industry works to fight the HLB disease carrying Asian Citrus Psyllid from destroying the industry, the California Citrus Clonal Protection Program is playing a key role in preparing the industry for battle. Watch this interview with Georgios Vidalakis, Director of the program as he explains. Read more in California Fresh Fruit Magazine.
Sacramento, Calif., (January 18, 2018) – The gypsy moth, an interloper from Europe and Asia, is threatening California’s majestic oaks in Ventura County.
Invasive desert knapweed, which comes from Africa, has made its first North American appearance in in California’s Anza-Borrego Desert, where it has started to crowd out native plants.
Asian citrus psyllids are slowly spreading the devastating huanglongbing disease in Southern California citrus.
River rats from South America, called nutrias, are munching voraciously on wetland plants in some areas of Stanislaus, Merced and Fresno counties.
These are just a few of the insects, weeds, animals and diseases that have entered the state of California from elsewhere on the globe, causing tremendous ecological damage and huge economic losses to agricultural crops, which ultimately affect every resident of California.
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.
A diverse group of university scientists, federal and state government representatives, county agricultural commissioners and non-profit organization leaders who are battling these pests converged at a summit in the state capitol Jan. 11 and 12 to coordinate their efforts, pool intellectual resources, and plot a strategy for protecting agricultural crops, natural resources, unique ecological communities, cityscapes and residential neighborhoods.
“We are a big, beautiful, special place, blessed with great weather and diverse geography,” said California Department of Food and Agriculture Secretary Karen Ross at the summit. “That means a lot to our many visitors – including pests.”
Glenda Humiston, vice president of UC Agriculture and Natural Resources, said research is a fundamental component of the fight against damaging 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. “I am so pleased with the numbers of people here today, and the expertise that you bring.”
A fundamental component of the fight against damaging invasive species is research, Humiston said, adding that the European grapevine moth in an apt example. The pest was detected in California’s wine country in 2009, and later found as far south as Fresno County. A multi-agency collaboration responded quickly.
UC ANR academics studied the moth’s biology, life cycle, host range and proven management practices. They developed a pest management program that relied on mating disruption with pheromones and application of carefully timed insecticides. In short order, the moth population plummeted, and the state was declared free of European grapevine moth, lifting a quarantine, enhancing farmers’ ability to export its product, and preserving the communities’ economic wellbeing.
“This multi-agency collaboration contributed to a successful, science-based response plan to a serious pest threat,” Humiston said.
She noted, however, that prevention is the best option.
“This is critical,” Humiston said. “Once the pests are here, they cost us millions upon millions of dollars to manage, not to mention the devastation and destruction inflicted on our crops, natural resources and the damage to local economies.”
In 2010, CDFA created a strategic framework for addressing California’s ongoing invasive pest problems and potential future introductions. Successful implementation of the framework requires partnerships involving government from the state to local levels, the agriculture industry and commodity groups, non-governmental organizations committed to the environment, and researchers at UC and other universities.
UC Cooperative Extension advisor emeritus John Kabashima led a break out session on arthropods during the summit.
UC Cooperative Extension advisor emeritus John Kabashima was instrumental in bringing the summit to fruition. Kabashima, who retired in 2015, continues to lead a battle against invasive shot hole borer pests in Southern California. The insects, originally from Asia, are killing thousands of Southern California trees, and have the potential to kill millions of trees in urban areas, natural areas and even on farms in parts of the state as far north as Sacramento.
“We convened this meeting to bring together experts in the field and people who are feeling the impacts,” Kabashima said. “We’re trying to start a 21st century invasive pest program that would then be implemented and funded to address the urgent issues before they cause any more devastation.”
At the end of the two-day summit, the participants voted to decide the most pressing issues and best strategies to take forward to their agencies, coalitions, research groups, legislators and constituents. Key strategies that emerged were:
Analyze the economic impacts of invasive species management and the cost of “doing nothing.”
Develop and maintain statewide surveys and map high-risk surveys.
Increase funding to study invasive species’ biology.
Create a standing rapid response workgroup to guide response to new invasive species. Fund a rapid response emergency fund.
Enact regulations to control high-risk vectors, such as soil, green waste, gravel, forage, straw and firewood.
Formalize the Invasive Species Council of California (ISCC) and the California Invasive Species Advisory Committee (CISAC).
Mark Hoddle, UC Cooperative Extension biological control specialist and director of the Center for Invasive Species Research at UC Riverside, said the summit was a valuable part of the ongoing battle against invasive pests.
Summit participants prepare to vote on most pressing invasive species’ issues and best management strategies.
“It’s good to see the number of agencies and organizations involved with invasive species issues,” Hoddle said. “I’m impressed with the energy in coming up with these priority lists.”
Summit outcomes will include sending recommended action items to the Legislature for funding consideration.
“Without financial support, many of the management tools that prevent unwanted incursions, find and monitor incipient pest populations, and develop sustainable, cost-effective management programs won’t be possible,” Hoddle said.
The bacterial causing agent of Huanglongbing (HLB), the deadly citrus greening disease threatening CA citrus production, is known as Candidatus Liberibacter asiaticus (CLas). Researchers looking into the change in the microbial community of a citrus tree when CLas takes over can help the industry develop effective early detection technology for HLB when it hits the orchard, according to plant pathologist Johan Leveau. Watch Leveau’s brief interview and read California Fresh Fruit Magazine to learn more.
Figure 2.
