Subtropical Fruit Crops Research & Education
University of California
Subtropical Fruit Crops Research & Education

Posts Tagged: ACP

Dogs on The Trail of HLB

A team of dogs trained to identify Huanglongbing-infected citrus trees by scent has detected evidence of early HLB infection in commercial groves in Ventura County.

The canine visit was arranged on behalf of the ACP-HLB Task Force by Farm Bureau of Ventura County, which signed a contract with the commercial company that trains and manages the dog teams. Four dogs and two handlers from F1K9, along with the company's operations manager, departed from Florida on July 24 and arrived in Ventura on July 26. Grove scouting began July 29 and ended Aug. 1.

During that time, the team inspected approximately 3,500 trees on 20 ranches in three major citrus production areas: the Las Posas Valley, the Santa Clara River valley, and the Ojai Valley. The dogs alerted on 211 trees, indicating early HLB infection is present in all three areas.

In preparation for the scouting visit, we prioritized potential locations on the basis of four criteria:(1) the presence of "hot spots" where plant and/or ACP samples yielded inconclusive DNA test results during the California Department of Food and Agriculture's periodic HLB surveys; (2) proximity to major transportation arteries; (3) a long history of established Asian citrus psyllid populations; and (4) a low level of participation in ACP suppression efforts by both growers and homeowners.

We also sought volunteers who would allow their ranches to be scouted, agree to pay for the cost (about $4.50 per tree), and agree to remove suspect trees. We agreed to keep the specific locations confidential unless granted permission to share that information by the owner.

The ranches the dogs scouted included one west of Fillmore along Highway 126, one west of Santa Paula without highway frontage, eight at the east end of the Ojai Valley, one outside of Moorpark along Highway 23, one north of Somis without highway frontage, and nine along a 4-mile stretch of Highway 118 west of Somis.

The dogs alerted on a single tree at one of the eight ranches they scouted in the Ojai Valley. Dogs indicated early HLB infection in multiple trees at every other location they scouted.

Although more than 1,600 HLB-infected trees have been confirmed and removed in urban yards in Los Angeles, Orange and Riverside counties, the recent dog alerts here are the first evidence of widespread HLB infection in commercial citrus in California. It is also the first time this early detection technique (EDT) has been deployed for non-experimental purposes, as a tool for commercial growers to make decisions about tree removal to potentially eliminate sources of infection and halt or delay the epidemic's spread. (Up-to-date summaries of the HLB epidemic can be found here:

Because neither the U.S. Department of Agriculture nor the California Department of Food and Agriculture recognize dog alerts as direct proof of the presence of the causal agent of HLB, the canine alerts do not trigger regulatory action. This allows growers to remove suspect trees voluntarily without the complications and cost associated with quarantine requirements that would be triggered by confirmation through official DNA testing.

Despite their non-regulatory status, the dogs' ability to accurately identify early HLB infection in citrus trees has been scientifically demonstrated and validated. The four canines that traveled to Ventura County last month are part of a 19-dog group trained to detect HLB through a multi-year research and development program funded by the U.S. Department of Agriculture and overseen by Dr. Tim Gottwald at the USDA research station in Fort Pierce, Fla. Dr. Gottwald has presented updates on the project at the last four International Research Conferences on HLB, including the most recent one this year in Riverside, as well as at many other scientific gatherings. One of his presentations on the project is available to view online.

The dog's indication of early HLB infection in local commercial groves is a watershed moment in the history of Ventura County's citrus industry. We've long known this day would come, but that doesn't prevent the news from landing as a gut punch. The knowledge we are gaining through strategic deployment of the canine team, however, gives growers here a fighting chance to stem the epidemic's spread while there is still time to do so

And so far, the distribution pattern of dog-alert trees - in general, widely scattered along grove perimeters - suggests we may be catching the epidemic in its very early stages. If this proves to be the case countywide, prompt tree removal and a zero-tolerance policy toward the Asian citrus psyllid - meaning total commitment to the ACP-suppression treatment program - may buy us years of continued viability and profitability even in the face of this threat.

To that point, it is more critical than ever for ACP to be well-controlled: No psyllids means no spread of disease. Growers should continue to treat when asked to for the area-wide treatments. But in addition, Dr. Beth Grafton-Cardwell of UC Riverside now recommends that perimeters be scouted every two weeks, and if psyllid eggs or nymphs are found, that the orchard be treated immediately. These additional treatments, above and beyond the area-wide treatments, must be applied whenever psyllids are found, to keep ACP suppressed below detectable levels.

We are planning to bring the dogs back out for additional scouting as soon as it is feasible. We need to visit other areas that meet the risk-factor prioritization test, so we can establish a baseline picture of how HLB is distributed throughout the county. This will help guide our ACP-suppression and HLB-eradication strategy going forward.

Potential participants are welcome to contact Farm Bureau CEO John Krist for inclusion on the list of properties prioritized for future scouting, so long as they are willing to pay for the cost (currently estimated at about $4.50 per tree), and agree to remove suspect trees. The dogs' time is too valuable and their availability too limited to deploy them where the information they provide won't be acted upon. Ultimately, our intent is to have a team based here permanently, but that will take time and money. We're exploring ways to make it happen.

For a full report on the Ventura County scouting visit, including documents describing the scientific basis of the canine program, go to

dog survey
dog survey

Posted on Friday, August 30, 2019 at 6:08 AM
Tags: acp (86), citrus (338), dogs (4), hlb (71)

HLB-Positive Psyllid Find

An Asian citrus psyllid (ACP) sample – confirmed positive for Candidatus Liberibacter asiaticus (CLas) – was collected approximately seven miles south of the U.S.-Mexico border on the eastern outskirts of Tijuana, Mexico earlier this month. This area does not have any commercial citrus production or nurseries nearby.

This is the first time that a CLas-positive psyllid sample has been found in the area since the United States Department of Agriculture (USDA) began its cooperative program with Mexico. The USDA works cooperatively with Mexico to conduct area wide treatments, biocontrol and surveys in the border region to help prevent the spread of Huanglongbing (HLB). A 400-meter radius around the find site is being treated. Additional ACP samples in the same area are being collected for testing. This ACP detection does not result in a U.S. quarantine expansion.

The best way prevent the spread of ACP into commercial citrus groves is to monitor for the pest and disease symptoms and follow the UC Integrated Pest Management treatment guidelines: Do not move citrus plants, foliage or fruit into or out of your area, and especially across state or international borders. This could unknowingly contribute to spread of the pest and disease.

If you see suspect ACP or HLB symptoms in your orchard, please notify the California Department of Food and Agriculture Pest Hotline immediately at 800-491-1899.


ACP mounted
ACP mounted

Posted on Thursday, August 29, 2019 at 8:28 AM
Tags: acp (86), citrus (338), hlb (71)

Where Is HLB? Where is ACP? In California?

The Asian Citrus Psyllid Distribution and Management Site provides you with a zoomable map to view psyllids, HLB, Psyllid Management areas, parasite releases and management information.  But if you are on the go, and would like to simply see on your phone where HLB infected trees are in relation to your orchard, you can use the HLB Grower App.  It's a web-based app found by entering into your phone browser, which you can then bookmark for future reference.  The HLBgrowerApp provides a zoomable map or address bar to locate your orchard.  When you click on the location of the orchard, it creates a circle around that point on the map and tells you if the orchard is more than or less than 5 miles from a known HLB infection.  It also provides you with a link to the voluntary grower response plan posted on the CitrusInsider website.  The voluntary grower response plan talks about what you can do to intensify protection against psyllids and HLB as the disease approaches your region.   

Scan for the HLB App:

hlb map
hlb map

Posted on Tuesday, August 27, 2019 at 7:32 AM
  • Author: Elizabeth Grafton-Cardwell
Tags: acp (86), citrus (338), hlb (71), psyllid (5)

HLB Early Detection?

Citrus Huanglongbing (HLB), also known as greening, is one of the most serious citrus plant diseases in the world. Infected trees produce bitter fruits that are green, misshapen, and unsuitable for sale. Once a tree is infected, there is no cure and it typically dies within a few years. Greening has already devastated the Florida citrus industry and poses a threat to California and Texas as well as Australia and the Mediterranean region.

Currently the most effective ways to prevent the spread of HLB are to stop the causal agent (Candidatus Liberibacter asiaticus) using quarantine measures, control the insect that spreads the disease (Asian citrus psyllid), remove the diseased trees, and plant HLB free trees. To this end, early diagnosis of HLB-diseased trees is crucial. Traditionally, diagnosis relies on observing blotchy mottle symptoms and confirming disease presence using molecular tools. However, these symptoms do not show until months after disease transmission and by then the disease has likely already spread throughout the grove.

Professor Nian Wang and his postdoctoral research associate Dr. Sheo Shanker Pandey, both from Citrus Research and Education Center, Department of Microbiology and Cell Science, at the Institute of Food and Agricultural Sciences of University of Florida, developed a strategy for early diagnosis of HLB before the appearance of blotchy mottle symptoms. They used a low-cost staining method to identify insect feeding sites and tested those identified sites for the causal agent using quantitative real-time PCR (polymerase chain reaction).

Through this method, the pair were able to detect the HLB causal agent up to two days after transmission and long before the appearance of symptoms. This early detection will enable citrus growers to prevent the spread of HLB in their fields. This finding is especially crucial for California, Texas, Australia, and the Mediterranean region as those areas are currently plagued by HLB.


More details about this study can be found in "Targeted Early Detection of Citrus Huanglongbing Causal Agent 'Candidatus Liberibacter asiaticus' Before Symptom Expression" in Phytopathology Volume 109, Number 6, published June 2019.

The appearance of HLB symptoms in 5-month-old cultivar Valencia seedlings fed by Asian citrus psyllid for 2 to 20 days. The HLB symptoms were monitored at 30, 60, and 90 days postinoculation (dpi). Representative images of HLB symptom development are shown. Photo: Sheo Shankar Pandey and Nian Wang

HLB symptoms post inocculation
HLB symptoms post inocculation

Posted on Monday, August 26, 2019 at 6:01 AM
Tags: acp (86), asian citrus psyllid (57), citrus (338), hlb (71), huanglongbing (66)

Santa Barbara ACP News


Cressida Silvers

ACP/HLB Grower Liaison

Ventura, Santa Barbara and San Luis Obispo Counties

805 284-3310

Reminder of 2019 Fall ACP Area Wide Management Schedule

September 8 - 21: Carpinteria, Summerland, Montecito

September 15 - 28: Santa Barbara, Goleta, and the rest of the county


Here is the University of California website on ACP monitoring techniques and management recommendations:

If you are restricted in your choice of materials, applications of horticultural oil can be effective.

Remember to notify beekeepers in your area before treating by contacting the County Ag Department at 805 681-5600. Get additional information about the new on-line bee registration and notification system BeeWhere at .

ACP continues to be difficult to find in the field. This is a good thing, and we want to keep it that way, so please keep up the good work by continuing to monitor your trees and participate in the Area Wide Management Program.

Remember, difficulty finding ACP does not mean it is not present in the orchard, or not in surrounding residential citrus. The fact that ACP adults continue to show up in yellow sticky traps throughout the south county is a reminder of this. 


Secretary Ross Visits Santa Barbara County

CDFA Secretary Karen Ross visited Santa Barbara County last month to hear first hand how neighboring cannabis operations are impacting existing agriculture. Several citrus growers, PCAs, applicators, and I had the honor of speaking with Secretary Ross, along with representatives from the governor's office, CDFA, and the county agricultural commissioner's office. 


HLB Update

The most recent map and totals for all HLB detections in the state are posted at the website  As of August 2, a total of 1,534 trees and 256 ACP have tested positive for the HLB bacterium, on a total of 1,110 sites, all still in LA, Orange, and Riverside Counties. To date, all HLB detections have been on residential properties, the infected trees have been or are being removed, and ACP treatments applied on a recurring basis to remaining citrus in those areas. No HLB has been found in commercial groves.

Voluntary Best Practices for HLB protection

As HLB detections increase and spread, it's important to be aware of possible actions you could take to further protect your citrus should an HLB detection occur in your area. These Voluntary Best Practices can be found at the Citrus Insider website HERE.

Regulatory responses required by the state in response to an HLB detection are described in CDFA's Action Plan for ACP and HLB . 

 -- All meeting agendas and eventually the minutes are posted at . All meetings are free and open to the public, and accessible via phone/webinar.  

  • Operations and Outreach Subcommittees meeting date has changed to Wed, Aug 21. Outreach agenda is here, Operations Agenda is pending.

Additional Useful Links:

Summaries of the latest scientific research on combating HLB:

Science-based analyses to guide policy decisions, logistics, and operations:

General updates and information on the state ACP/HLB program and regional activities: 

ACP mounted
ACP mounted

Posted on Wednesday, August 14, 2019 at 6:49 AM
Tags: acp (86), area-wide spray (2), citrus (338), hlb (71), huanglongbing (66), psyllids (3)

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