- Author: Ben Faber
A $1.5 million emergency grant is enabling UC Riverside scientists to find plants impervious to a disease threatening America's citrus fruit supply.
Citrus Greening Disease — also known as Huanglongbing, or HLB — results in fruit that is bitter and worthless. It has crippled Florida's citrus industry and has already been detected in California, which grows 80% of America's fresh citrus. An estimated 267,000 acres of Golden State oranges, lemons, grapefruits, and mandarins are at stake.
For these reasons, the National Institute of Food and Agriculture is supporting scientists at UCR, the University of Florida, and the U.S. Department of Agriculture's Agricultural Research Service in their search for plants with natural tolerance to HLB.
“If you find a disease affecting your crops, a good first step is to look for plants that are able to grow and produce despite infection,” said UCR geneticist Danelle Seymour. “Then you can start to identify the genetic basis of the disease tolerance and make sure the next generation of plants includes these genes.”
Following this recipe, Seymour and UCR plant pathologist Philippe Rolshausen will examine a set of 350 citrus hybrids developed and grown by project collaborators in Florida. All trees in the set are already infected with HLB, yet they live longer, are healthier, and yield more fruit than their infected relatives.
While there are a number of projects searching for different solutions to the threat of HLB, this project is different because the plants being tested were all grown in an environment endemic to the disease. Additionally, the number of plants they're able to test is unusually large.
“The environment in which these plants were grown means we can be confident that these rootstocks will enhance tree health and yield in HLB-affected areas,” Seymour said. “Also, because our data set is so large, we've got the opportunity to identify plants with levels of tolerance that exceed current commercial varieties.”
In addition to searching for parts of the hearty hybrids' genomes responsible for their tolerance to HLB, scientists will also be checking for plants that have resistance to other pathogens that are already in California.
Citrus in the state is also threatened by nematodes that chew up roots, preventing plants from taking up nutrients, and by phytophthora, a type of water mold that causes rotting roots.
By searching not only for a solution to the looming threat of HLB but also to problems that have already taken root in California, scientists are hoping to ensure that citrus won't need to be imported from HLB-free countries and costs stay low for both local growers and consumers.
“This way, we're making sure the next generation of rootstocks will include the right genes and that we're being as efficient as possible in our breeding practices,” Seymour said.
ACP nymph image by Sam Droege, USGS
- Author: Ben Faber
Huanglongbing Update
As of November 5, a total of 2,619 trees and 368 ACP have tested positive via PCR for the bacterium that causes HLB. The most recent activity has been in Orange and San Bernardino counties. Infected trees have been or are being removed, additional HLB detection surveys and ACP treatments are applied on a recurring basis to remaining citrus in those areas.
For additional details, please see the updated HLB quarantine and treatment map and table at maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf.
For information on regulatory and treatment requirements growers can expect should HLB be detected in or near your citrus grove or packing house, please refer to CDFA's Information for Citrus Growers/Grove Managers, Action Plan for ACP and HLB or this summary flyer.
Regulatory Update
Mustang Maxx has been approved for Spray and Harvest. For growers who harvest in one ACP Regional Quarantine Zone and pack in another, and use Spray and Harvest as their mitigation for moving bulk citrus, the list of approved ACP materials has been updated. The most recent list and protocols for quarantine compliance can always be found in the Information for Growers/Grove Managers document from CDFA. Please keep in mind this is separate and distinct from protocols and materials for Area Wide Management, discussed above.
Additional ACP/HLB Resources
- Check out the new and improved CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
oUC IPM recommendations for ACP
oWeb-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
oVideo on Best Practices in the Field, available in English and Spanish
- Research
oUC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
- Regulatory/Quarantine
oSign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
oRegulatory requirements for moving bulk citrus: Information for Citrus Growers
oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
- Author: Ben Faber
Commercial Citrus – How will the citrus grower manage the pest and disease in commercial groves?
The deadly huanglongbing (HLB) is spreading in California and threatens commercial citrus production. This website provides a map of where the Asian citrus psyllid (ACP) and HLB disease are located. Since there is currently no cure for the disease, the best management strategy is reducing the psyllid vector with insecticides and removing HLB-infected trees. This website provides a list of the ACP-effective insecticides, information about the best timing of their use & strategies for treatment.
Residential Citrus – What should I do to protect the citrus in my yard?
There is currently no cure for the huanglongbing (HLB) disease that kills citrus trees and is spread by an insect, the Asian citrus psyllid. It is estimated that 60% of Californians have at least one citrus tree in their yard, meaning that HLB may have a devastating effect in residential areas of California. Currently the only way to control the disease is to reduce the psyllid that spreads it and to remove trees that are infected or located near known infections. This website provides information about how near the insect and disease are to your home, and what you can do to help protect your trees.
How can I help educate the public on this very important subject?
This site has important resources for you to use to teach others about Asian citrus psyllid and huanglongbing.
Watch the 4-minute video below to learn what you can do to help control Asian citrus psyllid & HLB
Authors of this website are Dr. Matt Daugherty and Dr. Beth Grafton-Cardwell (retired) Extension Specialists in the Department of Entomology, UC Riverside, and Robert Johnson with UC Agriculture & Natural Resources, Informatics & GIS Statewide Program
/h2>/span>- Author: Ben Faber
It turns out, specially trained dogs can find citrus trees infested with Asian Citrus Psyllid (ACP). Canine Detection Services in Fresno has a grant from USDA to provide dogs that will sniff out the insects. The grant runs until March 2022.
The dogs are trained to sniff out ACP using training aids which contain ACP scent which does not have the bacterium causing the disease. The dogs run a pattern within an orchard or along the perimeter of the orchard. Dogs will sniff all sides of the trees in a given pattern. Depending on the environmental conditions, the dogs can smell the psyllid within 22 feet of an infested tree.
Canine Detection Services is also working with CDFA inspectors in residential neighborhoods, according to Victoria Hornbaker, director of the Citrus Pest and Disease Prevention Division within the CDFA. In this instance, the dog handlers shadow CDFA inspectors as they survey residential citrus trees for the pest and disease.
Hornbaker says the dogs can be a valuable tool for state inspectors to survey neighborhoods more quickly. If a dog alerts on a tree, inspectors can investigate for ACP adults or nymphs, and collect insect samples. This is also done in conjunction with surveys for the HLB disease.
The dog team services are free to commercial growers in California, Arizona, and Texas through next March, according to Finke. To schedule a visit or for answers to specific questions, contact Lisa Finke by email at lisa@canine-detection.com.
- Author: Ben Faber
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