- Author: Jeannette E. Warnert
A tell-tale sign of spring in California is a flush of new leaf growth on citrus trees. Because the feathery light green leaves are particularly attractive to Asian citrus psyllids (ACP), the leaves' emergence marks a critical time to determine whether the pest has infested trees.
“We encourage home citrus growers and farmers to go out with a magnifying glass or hand lens and look closely at the new growth,” said Beth Grafton-Cardwell, UC Agriculture and Natural Resources (UC ANR) citrus entomologist. “Look for the various stages of the psyllid – small yellow eggs, sesame-seed sized yellow ACP young with curly white tubules, or aphid-like adults that perch with their hind quarters angled up.”
Pictures of the Asian citrus psyllids and its life stages are on the UC ANR website at http://ucanr.edu/acp. If you find signs of the insect, call the California Food and Agriculture (CDFA) Exotic Pest Hotline at (800) 491-1899.
Asian citrus psyllids are feared because they can spread huanglongbing (HLB) disease, an incurable condition that first causes yellow mottling on the leaves and later sour, misshapen fruit before killing the tree. ACP, native of Pakistan, Afghanistan and other tropical and subtropics regions of Asian, was first detected in California in 2008. Everywhere Asian citrus psyllids have appeared – including Florida and Texas – the pests have found and spread the disease. A few HLB-infected trees have been located in urban Los Angeles County. They were quickly removed by CDFA officials.
“In California, we are working hard to keep the population of ACP as low as possible until researchers can find a cure for the disease,” Grafton-Cardwell said. “We need the help of citrus farmers and home gardeners.”
Grafton-Cardwell has spearheaded the development of the UC ANR ACP website for citrus growers and citrus homeowners that provides help in finding the pest and what to do next. The site has an interactive map tool to locate residences and farms that are in areas where the psyllid has already become established, and areas where they are posing a risk to the citrus industry and must be aggressively treated by county officials.
The website outlines biological control efforts that are underway, and directions for insecticidal control, if it is needed. An online calculator on the website allows farmers and homeowners to determine their potential costs for using insecticides.
There are additional measures that can be taken to support the fight against ACP and HLB in California.
- When planting new citrus trees, only purchase the trees from reputable nurseries. Do not accept tree cuttings or budwood from friends or relatives.
- After pruning or cutting down a citrus tree, dry out the green waste or double bag it to make sure that live psyllids won't ride into another region on the foliage.
- Control ants in and near citrus trees with bait stations. Scientists have released natural enemies of ACP in Southern California to help keep the pest in check. However, ants will protect ACP from the natural enemies. Ants favor the presence of ACP because the psyllid produces honeydew, a food source for ants.
- Learn more about the Asian citrus psyllid and huanglongbing disease by reading the detailed pest note on UC ANR's Statewide Integrated Pest Management website.
- Assist in the control of ACP by supporting CDFA insecticide treatments of your citrus or treating the citrus yourself when psyllids are present.
- Support the removal of HLB-infected trees.
- Author: Ben Faber
To help Ventura County's citrus community better understand the nature of the ACP epidemic — and the bitter lessons from Florida's failure to address it proactively — Farm Bureau and the ACP-HLB Task Force will host a workshop on Dec. 2. As speakers, we've invited three experts whose presentations were among the most compelling at last February's International Research Conference on HLB in Florida:
- Mike Irey, director of research and business development for Southern Gardens Citrus (which farms nearly 15,000 acres of oranges in Florida), who will speak about conditions in his state and provide an industry perspective on what it's like to live with HLB for a decade;
- Dr. David Bartels, an entomologist at the U.S. Department of Agriculture's Mission Laboratory in Texas, who will discuss his analysis of HLB survey data and what it can tell us about possible HLB infection sites throughout Southern California;
- Dr. Neil McRoberts, an epidemiologist and associate professor of plant pathology atUC Davis, whose computer modeling and research into the economic and social factors affecting disease spread can help guide development of an HLB management strategy for California.
The workshop will be from 1 to 4 p.m. on Wednesday, Dec. 2, at the Museum of Ventura County, 100 E. Main St., Ventura. It's free, but RSVPs are required. Please contact us at info@farmbureauvc.com or (805) 289-0155 if you plan to attend.
- Author: John Krist
On Aug. 30, Ventura County's citrus growers, pest-control advisers (PCAs) and pest-control operators (PCOs) embarked on the most ambitious program of Asian citrus psyllid suppression in commercial groves ever undertaken in California. The program involves coordinated pesticide treatments across more than 15,000 acres of citrus in the Santa Clara, Las Posas and Santa Rosa valleys. Hundreds of growers, PCAs, PCOs, grove managers and packinghouse field staff — aided by our county's two grower liaisons and the local ACP-HLB Task Force — are working together to pull it off.
This is the second cycle of area-wide management (AWM) treatments in Ventura County. The first was carried out from January through March in the east end of the Santa Clara River Valley. It involved eight of the county's 49 psyllid management areas PMAs and achieved good compliance, with 87 percent of the total acreage being treated (the rate within individual PMAs ranged from 80 percent to 93 percent).
The current cycle, however, involves 36 PMAs, vastly increasing the program's complexity. It also increases the workload for our PCAs and PCOs, and amplifies the consequences of any disruption in the timetable, which requires that all the citrus in each PMA be treated within a narrow two-week window.
And disruptions are precisely what the program has encountered. The extended periods of extreme heat that have cooked the county over the past two months have idled equipment and crews. At the same time, explosions of other pests — particularly broad mite, flaring under the unusually tropical conditions — have diverted resources to non-ACP treatments to avoid immediate economic harm from damaged fruit.
It remains to be seen whether the crews will be able to get back on track, and finish the fall AWM cycle by the end of November as planned. There is also the chance the applicator crews will encounter further delays, either in the form of extreme heat, Santa Ana winds or early rains associated with the strengthening El Niño condition in the Pacific.
As I have reminded members of Ventura county's citrus community numerous times since we began planning the transition to AWM, our program at this stage is a huge experiment with statewide ramifications.
We can't really draw lessons from areas outside California that are attempting area-wide suppression efforts (Texas and Florida) because their circumstances are so different. We have different weather and topography, for one thing. And Florida in particular did not even try to control ACP until most of the state was also infected with Huanglongbing (HLB) disease, so their program has struggled from the start. Our landscape is also quite different, with none of the giant citrus plantations of Florida and a much more complex pattern of intermingled smaller orchards and urban development than anything seen there or in Texas.
We also have little in common with the few other areas in California that are trying to implement AWM (mainly portions of Imperial and San Diego counties) because we have far more acreage and a much greater number of growers. Eventually, the San Joaquin Valley will find itself implementing AWM, at which point California will finally have an AWM program exceeding ours in scale. The very slow pace of ACP detections there, however, suggests that day is still well in the future.
For now, we have to figure out what works — and what doesn't — on our own. Trying to craft policies and protocols while also attempting to implement them is a bit like trying to build a race car while speeding down the track at 200 mph, but we have no other choice. Think of it as “adaptive management” on steroids.
There have been some very productive discussions among members of the Ventura County ACP-HLB Task Force and our hard-working PCA/PCO community, identifying data needs, logistical constraints and strategy options so we can continuously refine and improve the program. One of our chief challenges is adjusting for our equipment and spray crew limitations while still achieving effective ACP suppression, even when the weather and other pests refuse to cooperate.
One piece of very good news that has emerged at the midpoint of our fall AWM cycle is that the California Department of Food and Agriculture has been conducting timely treatments in urban yards within 400 meters of commercial citrus in each PMA. That did not happen last winter, and the result was swift re-infestation of commercial groves from ACP populations in neighboring landscape plants. At our request, and to CDFA's credit, the agency changed its policy and is no longer waiting to determine the level of grower participation before commencing those treatments.
Countering that, however, are scattered reports of growers refusing to participate — some even going so far as to switch packinghouses in order to avoid the policy instituted by responsible houses to suspend picking and packing fruit from an orchard during the PMA treatment window until the treatment has been conducted.
Evading the treatment requirement is irresponsible and fatally short-sighted. We know for a fact that HLB is less than 50 miles from us, and we also know for a fact that ACP from areas to the south — potentially even infected psyllids — is being transported into Ventura County in loads of bulk citrus. Just recently, a psyllid that tested “inconclusive” for HLB — neither positive nor negative — was collected in Piru. It may be a false alarm, and additional testing of psyllids at the same site will be conducted, but when clusters of such ACP have been found in the past, they have indicated locations where trees soon test positive for the disease.
Holdouts in the Ventura County citrus community must stop thinking of the ACP campaign as a battle against a bug, like so many other battles the industry has fought and won in the past. It is not. Ventura County citrus has never before confronted a tree-killing, insect-vectored disease epidemic, and the tools and strategies of conventional pest management will not stop or control it.
Save the date
To help Ventura County's citrus community better understand the nature of the epidemic — and the bitter lessons from Florida's failure to address it proactively — Farm Bureau and the ACP-HLB Task Force will host a workshop on Dec. 2. As speakers, we've invited three experts whose presentations were among the most compelling at last February's International Research Conference on HLB in Florida:
- Mike Irey, director of research and business development for Southern Gardens Citrus (which farms nearly 15,000 acres of oranges in Florida), who will speak about conditions in his state and provide an industry perspective on what it's like to live with HLB for a decade;
- Dr. David Bartels, an entomologist at the U.S. Department of Agriculture's Mission Laboratory in Texas, who will discuss his analysis of HLB survey data and what it can tell us about possible HLB infection sites throughout Southern California;
- Dr. Neil McRoberts, an epidemiologist and associate professor of plant pathology atUC Davis, whose computer modeling and research into the economic and social factors affecting disease spread can help guide development of an HLB management strategy for California.
The workshop will be from 1 to 4 p.m. on Wednesday, Dec. 2, at the Museum of Ventura County, 100 E. Main St., Ventura. It's free, but RSVPs are required. Please contact us at info@farmbureauvc.com or (805) 289-0155 if you plan to attend.
— John Krist is chief executive officer of the Farm Bureau of Ventura County. Contact him at john@farmbureauvc.com.
- Author: Ben Faber
There is some variability in citrus susceptibility to both the psyllid (Westbrook et al and Hall et al) and the bacterial infection (Shokrollah et al and Stover and Mc Collum). It is not fully clear at this point which of these species would be best to include in a breeding program, but both scions (http://www.concitver.com/3erEIIC2011/Viernes_23_sep/Ed_Stover/Ed_Stover.pdf) and rootstocks (http://www.flcitrusmutual.com/files/4cbb1e3c-1e1f-4b04-a.pdf) are being evaluated.
Some varieties like Australian Finger Lime (Microcitrus australasica) might show more resistance/tolerance to HLB than other species. At the UC Citrus Variety Collection website, it's possible to see the wide range of citrus species that are available for breeding and the commercial availability of those species. The collection is a view into the different materials that breeders can select from, in order to improve resistance to this citrus disease.
Citrus Variety Collection
http://www.citrusvariety.ucr.edu/
Australian Finger Lime Collection and Availability
http://www.citrusvariety.ucr.edu/citrus/microcitrus.html
Susceptibility to Infestation by Asian Citrus Psyllid
Catherine J. Westbrook1, David G. Hall2, Ed Stover, and Yong Ping Duan
http://www.ars.usda.gov/SP2UserFiles/Place/66180000/Westbrook%20et%20al%202011%20HortScience.pdf
D. Hall, C. Westbrook, Y.-P. Duan, E. Stover, R. Lee and M. Richardson http://citrusagents.ifas.ufl.edu/events/fl_citrus2011/Hall%20ACP%20IR%20Citrus%20Expo%202011.pdf
Susceptibility to HLB
Hajivand Shokrollah, Thohirah Lee Abdullah, Kamaruzaman Sijam,Siti Nor Akmar Abdullah and
Nur Ashikin Psyquay Abdullah
http://thescipub.com/PDF/ajabssp.2009.32.38.pdf
Ed Stoverand Greg McCollum
http://hortsci.ashspublications.org/content/46/10/1344.full.pdf+html
Photos
Australian Finger Lime Fruit
Australian Finger Lime Tree
- Author: Sonia Rios
- Author: Ben Faber
The Citrus Research Board in conjunction with the University of California Cooperative Extension (UCCE) held their annual grower seminar on Tuesday, June 30, 2015 at the University of California, Riverside (UCR) Palm Desert Center. Seminars also took place in Santa Paula, CA on June 25th and in Exeter, CA on July 1st. Speakers from all over the state from different agencies shared their knowledge and expertise with the group.
Mark Hoddle, a Biological Control Specialist at UCR gave an update of the biological control of Asian citrus psyllid (ACP). The ACP's natural enemy, Tamarixia radiata has been successful since its release in Southern California in 2011. The Tamarixia kills the ACP nymphs either by parasitizing them (i.e., females eggs laid underneath ACP nymphs and the parasitoid larvae burrow into the nymph to feed which kills the pest) or by host feeding (i.e., female parasitoids stab the nymph with their ovipositor, a tube that they use to lay eggs, and they feed on the body juices that leak from these wounds. This kills the nymph too). Hoddle reminded us, in order for this biocontrol program to continue to be successful, ant populations must be controlled. ACP nymphs produce a white, sugary waste product called honeydew, a good carbohydrate source for the ants, therefore, the ants will protect the nymphs from Tamarixia. His current research showed that when an ant population is reduced, parasitism control increases significantly. Hoddle and his lab will be testing different organic and conventional pesticides for their efficacy against Argentine ants in citrus orchards.
For example, he is in the works of helping produce a more effective ant-bait by working on a biodegradable hydrogel. These hydgrogels are made from algae and crab shells. The material is engineered to encapsulate a 25% sucrose solution with a tiny amount of pesticide and ant pheromone. The liquid bait "leaks" onto the surface of the hydrogel, ants drink it, take it to the nest and slowly intoxicate the queen and nest mates. The baits, about the size of a jellybean, will be engineered to have a certain life time before they "dissolve". He anticipates these jellybean like baits being able to be broadcasted under trees (like you would slug/snail pellets) and the pheromone will attract the ants to them. Once they start to feed, the ants will lay down their own trails to the baits. Mark Hoddle is also the director of the Center for Invasive Species Research, for more information regarding his work on biocontrol, please visit: http://cisr.ucr.edu/.
Victoria Hornbaker, from the California Citrus Pest & Disease Prevention Program Manager and grower Curtis Pate, also the grower liaison from Imperial gave updates on the current ACP management areas (Fig. 1). Curtis, reminded the growers, ACP is attracted to bright colors, such as yellow. Yellow is a common color for most safety vests and jackets, this creates an issue because most people that own one of these pieces of clothing are unaware that they can very well be unknowingly transporting this pest to different locations (Fig. 2). Basic measures such as rolling up vehicle windows, shaking off clothing
Lori Berger, with the UC Statewide Integrated Pest Management (IPM) Program gave an update on the Chlorpyrifos Critical Use Project (Fig. 3). The project is a multi-year effort to identify the pest management needs and practices for use of Chlorpyrifos in important crops in California. To accomplish this goal, Department of Pesticide regulation (DPR) contracted with UC IPM program to convene industry leaders to work together to create commodity specific guidelines for specific cropping systems. Chlorpyrifos is used on critical citrus pests such as ants, ACP, scales, bud mite, leafminers and many other arthropods. Growers are required to now obtain a restricted materials permit from their local County Agricultural Commission since DPR has designated the insecticide for restricted use in California as of July 1, 2015. The permit conditions may include buffer zones near sensitive sites, good management practices to reduce drift or offsite movement into the air and measures to reduce runoff into surface waters. For Southern California growers, a more in depth meeting will be held at the San Diego Farm Bureau in Escondido on September 15, 2015, more information on this meeting will available in the near future. DPR hours for laws and regulations will be available. More information on the Chlorpyrifos Critical Use Project can be found at: http://www.ipm.ucdavis.edu/IPMPROJECT/CDPR_Chlorpyrifos_critical_use_report.pdf.
Ben Faber, a UCCE Farm advisor from Ventura/Santa Barbra County gave a great presentation on how to interpret soils/water/leaf analyses and managing water in a drought. Soil and water reports are best used for identifying problems in: 1) pH (power of hydrogen); 2) salinity (how much salt is in the soil); 4) chloride (Cl-); 5) sodium (Na+); 6) boron (B); and 7) sodium adsorption ration. Most of the issues listed can be managed by leaching. Unfortunately, there are no definite measurements for fertility management of perennial crops, however, understanding the fundamentals of interpreting analyses is key for a healthy producing grove. For example, when one is handed a report, many may get overwhelmed by the sight of all these things that are reported. Many of those numbers are only on there because they are required to be there by law and may not have an importance to you as grower when it comes to management decisions. You may ask yourself, what is really important in all this? Faber, gave the growers a quick review, for example, in a water analyses we would want to look for look for some basic ranges in: Boron, this element should be no higher than 1 parts per million (ppm), sodium and chloride no higher than 100 ppm, and the TDS (total dissolved solids), this may also be known to some as EC (electrical conductivity), should be no higher than 1,000 ppm. Simple, right?
When dealing with pH, it is always best to balance that out before one plants trees. Trying to balance the pH after a crop has been established can be challenging and you may run the risk of injuring or killing your trees in the process. Those that would like to learn more on soils/water/leaf analyses and managing water in a drought, you can visit Ben Faber's UCCE County website: http://ceventura.ucanr.edu/Com_Ag/Subtropical/.
Neil McRoberts. Professor of Plant Pathology from UC Davis had interactive question and answer session with the audience, gathering grower's views on approaches of control for ACP/ Huanglongbing, also known as citrus greening disease. The answers to this survey will be helpful in creating a management plan to better help growers with their ACP treatment and preventative planning. Michelle Richey, assistant Director of Food Safety from Ott and Davison Consulting also gave a quick update on Food Safety and Good Agricultural Practices certification. She stressed on how important it is to keep records of everything that happens in a business and to have them accessible.
We had a great turn out and hope to see more growers at next year's Southern California meeting.