Posts Tagged: huanglongbing
Planting alternative backyard fruit trees in Southern California can help stop citrus threat
Southern California's mild Mediterranean climate makes it ideal for growing fruit trees in backyards, community gardens and school gardens. The trees provide wholesome fruit along with shade, beauty and enrichment for families and communities.
Citrus trees are favorites for Southern California backyards, but Surls and her team aim to get local gardeners thinking beyond lemons, limes, oranges and other citrus fruit. In the past several years, a deadly plant disease has been spreading among Southern California citrus, prompting quarantines and putting citrus orchards across the state at risk.
Surls and her team are working on an initiative with a corps of volunteer UC Master Gardeners in Los Angeles and surrounding counties to promote selection and planting of appropriate fruit trees. New brochures, a website, workshops and one-on-one consultations will guide Southern Californians in making tree decisions that are scientifically sound and community-focused.
The project addresses serious concerns about the rapid spread of huanglongbing (HLB) disease, also known as citrus greening. The insect that spreads HLB – the Asian citrus psyllid – was introduced into California in 2008. The disease made its first California appearance in a Los Angeles County backyard in 2012. HLB, which eventually kills every tree it infects, is now spreading rapidly in urban areas of Los Angeles and Orange counties, where quarantines have been put in place by the California Department of Food and Agriculture (CDFA).
“Citrus trees are so popular in Southern California. They are part of our history and regional identity,” Surls said. “Now we have the unfortunate responsibility of telling residents about this serious problem we are facing. In some cases, residents who live near infected trees should be proactive and remove their lemon, orange, mandarin and lime trees and replace them with different kinds of fruit.”
University of California Agriculture and Natural Resources IGIS programmers, in collaboration with UC Cooperative Extension, have created an HLB Monitoring Web App that allows residents to enter an address to determine how close they are to confirmed HLB outbreaks. If they are within 2 miles of a residence where an HLB-infected citrus tree was found, the app recommends replacement of citrus trees with non-citrus fruit trees, such as apples, peaches, avocados or persimmons.
Residents with citrus trees that are 2 to 5 miles from areas with HLB should keep a close eye on their trees, treat for Asian citrus psyllid and begin thinking about planting an alternative to citrus if the disease spreads to their area.
“Huanglongbing poses a serious threat to both backyard and commercial citrus in California if its spread is not halted,” Surls said. “By removing trees in areas where HLB has been found, residents are helping reduce its ability to spread, buying time for scientists to find a cure.”
CDFA is testing trees throughout the state and removing HLB-infected trees. However, the first visible symptoms of HLB – yellow mottled leaves – can appear months to years after infection. Even if they look perfectly healthy, citrus trees can be harboring the disease and allowing it to be spread by the tiny psyllid insect.
Current hotspots shown on the HLB Monitoring Web App include Rosemead, Montebello, Pico Rivera, San Gabriel, Hacienda Heights and Cerritos in Los Angeles County. In Orange County, HLB is spreading in communities around Garden Grove, Westminster and Santa Ana.
“We know removing citrus trees is going to be really hard for people,” Surls said. “But if you live within two miles of an infected tree, your tree is probably already infected, and HLB means your tree is going to die.”
To ease the transition, UC Master Gardeners are informing residents about alternatives that will produce fruit that's nutritious and delicious.
“So many types of fruit trees can be grown in Southern California,” Surls said. “Honestly, we have almost unlimited options. We live in a fruit tree grower's paradise. So we want to encourage local residents to think seriously about selecting non-citrus trees to replace their citrus.”
The information can also inform residents who are planning a new backyard orchard.
“They should consider some of the many wonderful fruit trees we can grow here — plant a pomegranate, plant a peach, plant a persimmon — but resist the temptation to plant more lemons, oranges and other citrus trees,” Surls said.
Making the decision to plant a certain type of tree should not be taken lightly.
“Planting a fruit tree is a big commitment. It will be part of your garden for years. Research the best options for your family and locations,” Surls said. “The UC Master Gardeners are here to help.”
Following are good options to consider for replacing citrus trees in Southern California, although recommendations may vary based on local climate:
Apples
Certain apple varieties that do not need to be exposed to cold temperatures grow and produce well in Southern California. Low-chill varieties include Anna, Beverly Hills, Dorset Golden, Fuji and Gala.
Figs
Figs grow well in full sun in Southern California. They can reach 10 to 30 feet tall, and are best for spacious areas.
Jujube
Jujubes are less common in Southern California, but are a valued fruit in Southeast Asian and will grow well under Southern California conditions. They grow about 15 feet tall. Jujubes are a good selection for inland valleys that get hot during the summer. The fruit tastes like small, crispy apples. Dried, they are similar to dates.
Loquat
A small- to medium-size tree that grows 10 to 20 feet high, loquats are easy to grow and have relatively few pests. Fresh, ripe loquats are sweet and aromatic. They can be used in jams, sauces and garnishes.
Persimmon
Persimmons ripen in autumn after the leaves have fallen, creating a beautiful landscape display. They are easy to grow in full sun and part shade. Persimmons can be eaten fresh or dried for a date-like fruit.
Pomegranate
Well-suited to Southern California's Mediterranean climate, pomegranates grow to about 15 feet in height. Pomegranates are pest- and disease-resistant. The fruit's seeds, coated with astringent juicy flesh, are called arils. Use arils to top salads or other dishes, or squeeze for juice or to make jelly.
Other fruit tree options for Southern California include mangos, guavas, pineapple guavas, peaches, nectarines and pears.
For more research-based information about alternative fruit trees, visit the UC Agriculture and Natural Resources website “California Backyard Orchard” at http://homeorchard.ucanr.edu.
Contact your local UC Master Gardener Program for additional advice:
Los Angeles County – http://celosangeles.ucanr.edu/UC_Master_Gardener_Program
Orange County – http://mgorange.ucanr.edu
Riverside County – https://ucanr.edu/sites/RiversideMG
San Bernardino County – http://mgsb.ucanr.edu
Ventura County – https://ucanr.edu/sites/VCMG
Funding for the ‘Alternatives to Citrus Fruit in the Fight against Huanglongbing Disease' project was made possible by the U.S. Department of Agriculture's (USDA) Agricultural Marketing Service through grant AM180100XXXXG003. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.
Screen installed over the 'parent navel' in Riverside to protect it from disease
City of Riverside staff draped a synthetic screen on a steel frame to encompass the 'parent navel' orange tree at the corner of Arlington and Magnolia avenues in Riverside to protect it from Asian citrus psyllids that spread huanglongbing disease, reported Ryan Hagen in the Riverside Press-Enterprise. Huanglongbing (HLB) is a devastating bacterial disease of citrus that is starting to spread rapidly in urban areas of Southern California.
The newly covered tree is valued for its status as an early ancestor of all Washington navel orange trees.
UC Cooperative Extension specialist Georgios Vidalakis, the UC Presidential Researcher for Sustainable Citrus Clonal Protection, was on site when the tree was enclosed within the new cover.
“This one will buy us a few years so the city can design a more elegant structure like you see in arboretums — maybe a wood hexagonal pavilion that will be aesthetically more pleasant,” Vidalakis said. “Unless in the next few years we find a solution.”
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.
Huanglongbing is a growing threat to California’s citrus industry
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.
View a four-minute video that shows how to monitor for ACP presence in residential citrus:
Riverside Washington Navel gets additional protection
The city of Riverside is taking steps to protect a 143-year-old Washington Navel orange tree - the tree that parented most navel oranges alive today, reported the Riverside Press-Enterprise.
According to legend, the seedless and sweet Washington navel was an accidental mutant that appeared on the grounds of a Brazil monastery in the early 1800s. Tree clones were sent to USDA in Washington, D.C., and from there acquired by Eliza Tibbets, who tended the trees at her home in Riverside.
This month, city workers removed two trees that were planted near the iconic navel orange - a Marsh Grapefruit and another navel, which was planted in the 1940s and doesn't have the historical value. They have built a steel structure over the Washington Navel to support a transparent screen that will keep out Asian citrus psyllid, an invasive pest that spreads the devastating huanglongbing virus in citrus.
The measures to protect the tree were planned by a team that includes scientists from UC Riverside, the Citrus Research Board and the USDA, the article said.
For more information on the photo above, see visit this UCLA Library page.
Dogs enlisted to sniff out disease in citrus trees
The Citrus Research Board is arranging to bring specially trained dogs to the UC Lindcove Research and Extension Center to test their ability to sniff out the devastating citrus disease huanglongbing, reported Bob Rodriguez in the Fresno Bee.
CRB president Gary Schulz is working with the USDA, which is training dogs in Florida to identify trees with huanglongbing soon after the trees are infected. HLB has ravaged Florida's citrus industry. In California, the disease has been found about 800 Southern California backyard trees, but officials have so far managed to keep it out of the state's commercial orchards.
"The USDA has invested million of dollars in detector dogs and they have proven to be a credible diagnostic tool for early detection and screening trees," Schulz said.
HLB is spread by Asian citrus psyllids. Psyllids can pick up the the disease from infected trees and spread it to other trees as they feed. Symptoms may not show up in the tree until a year or two after it is infected. PCR (polymerase chain reaction) is the only way to positively identify huanglongbing infection in citrus. The process requires testing of many leaves or branches from the tree and may return a false negative if the samples selected for testing aren't infected, but other parts of the tree are.
Schulz said the HLB-detection dogs will start their California work in the southern part of the state before traveling north.