Asian Citrus Psyllid (ACP)

Research Nets Going Over Citrus Trees To Prevent Huanglongbing Disease

Blocking Psyllids Carrying Disease is Key

By Jessica Theisman, Associate Editor

Beth Grafton-Cardwell is the director of the Lindcove Research Extension Center in Tulare County and research entomologist based out of the University of California, Riverside. She recently told California Ag Today that there is work being done on installing a net structure to protect trees from Asian Citrus Psyllids, which spread the deadly Huanglongbing disease. Texas A&M researchers are installing net structures on the edge of groves to block psyllids from coming into an orchard.

Psyllids have a preference for borders. These nets could have yellow sticky strips of material with an insecticide on it, so there would be an attract and kill process.

Beth Grafton-Cardwell

Other research is looking at netted structures that will completely enclose the citrus trees.

“Researchers are going to construct a completely enclosed net structure to grow the citrus trees in a block at Lindcove,” Grafton-Cardwell said. “We will study how well one can grow citrus under the screen so there could be the ultimate protection against pests and diseases.”

“The mother trees and increased trees have to be grown under the screen, but the field trees do not necessarily have to be,” she said.

Cold temperatures in the winter to protect the citrus from the psyllid.

“The cold temperatures hardened off the tissue, which makes it hard for the psyllid to find any place to lay eggs, and they probably cost some mortality to the psyllid,” Grafton-Cardwell explained.

Most outbreaks are in Southern California. Los Angeles, Orange County, and a few trees in Riverside.

“Prevention is working and there are fewer outbreaks in the Central Valley,” Grafton-Cardwell said.

Dr. Mark Hoddle and Dr. Kelsey Schall (both from UC Riverside) have been monitoring backyard situations. They are researching the release of beneficials such Tamarixia and other generalist predators like Syrphid flies.

“They have been reducing psyllids by about 70 percent in the backyards, and that’s really good news,” Grafton-Cardwell said.

2021-05-12T11:05:11-07:00June 15th, 2018|

New Study Reveals Economic Impact of California Citrus

Citrus Research Board Quantifies California Citrus Industry’s Importance

Edited by Patrick Cavanaugh
      Despite Tulare Mayor Carlton Jones posting a series of anti-ag comments on Facebook, causing a stir in the local community, agriculture provides a huge economic stimulus to his community. In fact, without agriculture in Tulare, the city would most likely be in economic ruin.
     Citrus is one crop that is grown in the county. And the total economic impact of the iconic California citrus industry is $7.117 billion according to a new study commissioned by the Citrus Research Board (CRB).
     “In updating our economic analysis, we selected a well-known expert, Bruce Babcock, Ph.D., a professor in the School of Public Policy at the University of California, Riverside, to conduct the research. His findings quantified the significant impact of citrus on California’s economic well-being,” CRB President Gary Schulz said.
     According to Babcock, the California citrus industry added $1.695 billion to the state’s Gross Domestic Product (GDP) in 2016.
     “California citrus is a major contributor to the economic value of the state’s agricultural sector and is much larger than just the value of its sales,” he said. “Estimated full-time equivalent California citrus jobs totaled 21,674 in 2016-17, and estimated wages paid by the industry during that same time frame totaled $452 million.”
     Babcock added, “The application of management skills and capital equipment to efficiently utilize land and water to produce high-quality citrus also generates upstream and downstream jobs and income that magnify the importance of citrus production beyond its farm value.”
     In 2016-17, the most recent marketing year of data compilation, Babcock found that the total direct value of California citrus production was $3.389 billion. This value generated an additional $1.263 billion in economic activity from related businesses that supplied materials and services to the citrus industry. Layered on top was another $2.464 billion in economic activity generated by household spending income that they received from California’s industry, according to Babcock, thus rendering a total economic impact of $7.117 billion.
     The study revealed that 79 percent of California’s citrus was packed for the fresh market and 21 percent was processed in 2016-17, which is economically significant because fresh market fruit has a higher value than processed fruit.
     Of further note, California produced about 95 percent of all U.S. mandarins in the most recent reporting season.
     California Citrus Mutual President Joel Nelsen said, “The ‘wow’ factor in this report is something, as it relates to gross revenues and positive impact for the state, people and local communities. This enthusiasm must be tempered by the fact that huanglongbing (HLB) can destroy all this in a matter of a year if the partnerships that exist between the industry and government cannot thwart the spread of this insidious disease. Just this week, coincidentally, Brazil authorities reported a 20% reduction in fruit volume. Reading how that would affect our family farmers, employees and the state is sobering.”
     The CRB study also looked at the possible impact of a potential 20 percent reduction in California citrus acreage or yield or a combination of the two that could result from increased costs associated with meeting government regulations, combatting the Asian citrus psyllid (ACP) and warding off the invasion of HLB, a devastating disease that has decimated citrus production in many other growing regions such as Florida. Babcock calculated that such a reduction could cause a loss of 7,350 jobs and $127 million in associated employment income and could reduce California’s GDP by $501 million in direct, indirect and induced impacts. The CRB currently is devoting most of its resources to battling ACP and HLB to help ensure the sustainability of California citrus.
     Babcock is a Fellow of the Agricultural and Applied Economics Association and has won numerous awards for his applied policy research. The economist received his Ph.D. in Agricultural and Resource Economics from the University of California, Berkeley, and his Masters and Bachelors degrees from the University of California, Davis.
     The CRB administers the California Citrus Research Program, the grower-funded and grower-directed program established in 1968 under the California Marketing Act as the mechanism enabling the State’s citrus producers to sponsor and support needed research. More information about the Citrus Research Board and the full report on the “Economic Impact of California’s Citrus Industry” may be found at 
2021-05-12T11:05:12-07:00May 21st, 2018|

Citrus Psyllid Control Strategy Changes

Reducing Sprays in Areas, and Border Nets

By Jessica Theisman, Associate Editor

Entomologist Beth Grafton-Cardwell

Huanglongbing, vectored by the Asian Citrus Psyllid, (ACP) is the dreaded disease that has nearly wiped out the Florida citrus industry and is a potential problem for citrus growers in California. California Ag Today recently met with Beth Grafton-Cardwell, a UC Cooperative Extension Specialist. She specializes in integrated pest management; she discussed new strategies for the control of HLB.

“We have been surveying grower orchards in southern California and following how pesticide sprays are working, and I’m going to make some new recommendations on how to handle the populations down there,” said Grafton-Cardwell, who is also the director of the Lindcove Research and Extension Center. “Some regions of Southern California are easier to control psyllids than others. The pesticide treatment is less intensive due to the desert climate. San Diego is one of the areas that is less intensive due to the drier trees making them more hardened off, with less new flushes, where ACP is attracted.”

“There are other areas of southern California where the trees flush continually, providing great places for the psyllids to lay eggs, and that is where treatments are going to have to intensify,” she explained.

Areas such as Ventura, Riverside, and San Bernardino have to increase their treatments in the fall for better control.

And researchers are currently studying new prevention and control methods.

“Texas A & M has been looking at erecting net-like borders around the orchards because the psyllid tends to go to the edges,” Grafton-Cardwell said.

They want to treat the netting with yellow strips of sticky paper that would attract and/or apply insecticides to kill the psyllid.

“Our research is showing that often the infestation starts on the borders. Growers may have to intensify the number of treatments, but they don’t have to treat the entire orchard,” Grafton-Cardwell said. “Growers might be able to fight the psyllid with only treating the trees on the outer edges.”

2021-05-12T11:05:12-07:00May 10th, 2018|

Relentless Search for ACP and HLB Trees

Intense Inspections of Urban Citrus Trees Continue

By Patrick Cavanaugh, Editor

Joel Nelsen is president and CEO of California Citrus Mutual, based in Exeter. He told California Ag Today recently that there is an “active plan to look for trees harboring Asian Citrus Psyllids (ACP) infected Huanglongbing (HLB) trees in urban areas because we’re looking for nobody else across this country, let alone in the southern hemisphere, to look for infected trees in the urban area. Mexico and Brazil didn’t do it. We’re doing it.”


Joel Nelsen

The hope is that they find HLB and stop it there.

“Commercial growers are under tight testing programs to combat the Asian Citrus Psyllid. As far as it relates to commercial growers, we’re doing enough trapping that we’re not finding what we call hot spots of Asian Citrus Psyllids,” Nelsen said. “Secondarily and most importantly, we have a very strict clonal protection program, so growers are only allowed to access trees after they’ve gone through a rigorous testing program at both the nursery and the rootstock from the university.”

Nelsen said that the chances of a grower introducing the insect into an area is rather slim; it’s more often likely that the disease will be introduced to a grove.

Testing is random and more lab space is needed.

“Most of it’s been random because it is an intensive program. We’re analyzing roughly 20,000 leaves and twigs every month,” Nelsen explained. “We’re analyzing several thousand ACP every month. In fact, our lab capacity is capped, and one of the discussions that we’re having is to identify what labs can do what and whether or not we need to expand the number of labs doing business.”

“So we are looking at additional lab space, and in fact, we have already contracted with the University of Arizona Lab in Tucson  and maybe we’ll consider using private labs to do the initial work,” Nelsen said. “Now, they’re not going to be able to confirm whether or not an ACP is there, but they go in and evaluate that twig or green waste waste and if in fact there is a suspicion, then you send in the California Department of Food and Agriculture folks.”

2021-05-12T11:01:55-07:00March 19th, 2018|

More Cooperation Regarding Citrus Health and HLB Disease

Citrus Health Response Program Discussed at UC Riverside

By Patrick Cavanaugh, Editor

California Ag Today recently interviewed Joel Nelsen, president and CEO of the California Citrus Mutual. He spoke on his recent trip to UC Riverside about the Citrus Health Response Program. While speaking with USDA, they discussed the game plans that will be used to battle Huanglongbing (HLB) disease, which is vectored by an invasive insect called Asian Citrus Psyllid.

“We got into it, which I thought was an interesting discussion. What would growers do if in fact HLB was discovered in a grower’s orchard and what would the be obligated to do,” Nelsen said.

“And what came out of that discussion is that we are going to work with the USDA. We’re going to develop a war game scenario. We’re going to bring people into a room and start talking about it, just to see what the reactions were, and we’re going to challenge these individuals to do what needs to be done,” Nelsen explained. “We’re just going to have to figure out how best to address the industry and areas like this.”

Nelsen said that they discussed whether or not there was enough being done in that partnership with the homeowner. “We came to the conclusion that no, quite frankly the industry has been carrying that ball and that USDA and CDFA can do a little bit more in their role as government”

Tree removal and beneficial insects were also discussed.

“We talked about the continued trees being removed, and everybody was satisfied about that. We talked about whether or not beneficial insects can help in this situation. Surprisingly, the answer was pretty much no,” Nelsen explained. “Beneficial releases may help in an urban environment to a small extent, but from a commercial standpoint, it doesn’t help. So there were a lot of discussions, some debate, and most of all, some camaraderie that was developed as far as going forward.”

Nearly 400 trees in front and back yards of homes have been destroyed due to testing positive to HLB disease.

“They’re all in a clearly defined geographical area in Southern California,” Nelsen said. “So what we have is a lot of backyard adventures that bring in rootstock that unfortunately was diseased, and as a result of that, those individuals are the ones that are seeing problems associated with their own trees.”

2021-05-12T11:01:56-07:00March 15th, 2018|

Fighting Huanglongbing Is Job One

Citrus Health Program Protecting State’s Industry

By Patrick Cavanaugh, Farm News Director

Joel Nelsen, president and CEO of the California Citrus Mutual based in Exeter, spoke to California Ag Today about a recent trip to UC Riverside to discuss the Citrus Health Response Program and huanglongbing disease.

“For the last several years, the federal government and the California citrus industry had a wonderful partnership with some ideas, some regulation, and most importantly, with some funds,” Nelsen said. “So periodically, USDA comes to do an audit as to what we’re doing, how we’re doing it, and whether or not there needs to be some reevaluation.”

“The Citrus Health Response Program is the program we call a CHRP for a two-day evaluation. You had scientists and regulators from USDA; you had regulators from CDFA, along with a few scientists,” Nelsen explained.

“You had that entire stakeholder group and members from the scientific community and UC Riverside to evaluate what we’re doing and why, but eventually we did achieve one objective and that’s coming up with several action steps that we need to do as an industry in partnership with government,” he said.

The concern of Huanglongbing disease was discussed and game plans were presented.

“What was interesting is this was a friendly audit. They weren’t interested in taking money away, they weren’t interested in determining if we’re using dollars appropriately, but they wanted us to talk about why we were still spraying in the urban environment for the Asian Citrus Psyllid, which vectors Huanglongbing,” Nelsen said.

“They wanted us to talk about whether or not growers were doing what they were supposed to be doing and of course, they are doing what they need to do to keep the deadly disease out of commercial citrus orchards,” Nelsen said.

2021-05-12T11:01:56-07:00March 8th, 2018|

Kern County Ag Commissioner Notes Mild Winter

Weather and Pest Control this Season In Kern County

By Jessica Theisman, Associate Editor

California Ag Today recently spoke with Glenn Fankhauser, Agricultural Commissioner for Kern County. He let us know his thoughts about the weather in his county this season.

He said it has been a mild winter and it may affect future crop production. “We are not sure how it is going to affect fruit set. It could be negative for some of our stone fruits and cherries, but on the bright side, the mild weather allows farmers to plant certain field and vegetable crops earlier than normal,” Frankhauser said. “The little rain and shortage of water will challenge growers again this year.”

Fankhauser says that Kern County is doing what they can to stop Huanglongbing (HLB) disease, which is spread by the Asian Citrus Psyllid (ACP).  HLB is the number one disease in citrus because once a tree is infected with a bacterium, it is deadly to the tree.

“We have our traps set, we are monitoring the levels, and we have a treatment coordinator that helps the growers to maximize their effect on the Asian Citrus Psyllid,” Frankhauser said.  “By making sure the treatments are precisely coordinated, they are able to knock down more of the populations. There have not been any positive HLB trees in Kern County.”

Of course, any trees that become positive to the disease are immediately destroyed.

“We also have a group of citrus growers who are visiting homeowners and gaining voluntary removal of citrus trees at home,” he said. “They pay a nominal amount of money to allow a citrus tree to be removed. Once removed, they replace the citrus tree with a non-citrus shade tree.”

2021-05-12T11:01:56-07:00February 28th, 2018|

Protecting California Citrus Industry

State’s Citrus Industry at a Crossroads

By Patrick Cavanaugh, Farm News Director

Karen Ross, Secretary of the California Department of Food and Agriculture, told California Ag Today recently that the fight to protect the California citrus industry from Citrus Greening is ongoing with many moving parts.

“We are working closely with both with USDA and county ag commissioners to protect our important citrus industry,” she said. “And funding from our federal agency partners is important in the fight.”

“There is a strong sense of urgency, and I honestly feel we’re at a significant crossroads because of the most recent Huanglongbing infected tree finds in Southern California that keep the infected Asian Citrus Psyllid numbers up,” Ross explained.

She noted that the biggest challenge is citrus in the state’s urban areas.

“The beauty of citrus is that nearly every Californian has a citrus plant of some kind. That’s also one of our biggest challenges right now, because we’re very dependent on our urban residential neighbors to allow inspectors to repeatedly go to their door, in order to take samples, and then possibly having to go back and pull trees.

Ross said that the state has dedicated full time leadership to help fight HLB. There’s a lot of moving parts in the program.

“It’s gotten very large, and we’re going do whatever we need to do to make sure California citrus has a long, long part of our history and our economy,” she said.

Ross noted that the Asian Citrus Psyllid isn’t the only pest concerning California agriculture.

“Besides our big Asian citrus psyllid program, we have ongoing medfly infestations, several fruit fly infestations, and light broth apple moth infestation, and we are working on Japanese beetle eradication programs,” she said.

2021-05-12T11:01:58-07:00October 31st, 2017|

Huanglongbing Top Importance in Citrus

Huanglongbing Disease in Citrus is Top Problem

By Patrick Cavanaugh Farm News Director

Gary Schulz, President of the Citrus Research Board in Visalia, said the pest pressure in citrus comes down to three problems.

“You know, there’s three really. There’s Huanglongbing, Huanglongbing, and Huanglongbing, (HLB)” Schulz said at the recent California Citrus Conference in Visalia. “When I moved to California in 1990, I had an old-timer that was on my board. He said, ‘You know, in California, we have three major challenges: water, water, and water.’ Well, in the citrus research for pests and diseases, it’s really Huanglongbing.”

Gary Schulz

“If we’re talking about red scale or Phytophthora or lemon fruit drop, those are important challenges, but if HLB begins infecting our commercial groves and spreads as rapidly as it can without our attention and treatment or tree removal, the rest are moot,” Schulz said.

He discussed his hope for the future of the California citrus industry.

“I hope that in five years, we’ve solved HLB. That’s my personal goal. Somebody’s got to put the stake in the ground and put a date out there,” he noted.

Schulz said that Citrus Research Board has got a number of research programs that are all working side by side to find that solution, turn that key, and make that happen.

“It may be more than just one solution. We have a researcher at Washington State University in Pullman for example. They’ve earned a research grant from the USDA because of the creativity in putting their work team together and the fact that they bring a whole new fresh approach and fresh thought process to how to culture the bacteria that causes HLB disease. That’s huge in the science community and has never been done before,” Schulz said.

For more information go to

2021-05-12T11:01:58-07:00October 17th, 2017|

Huanglongbing Discoveries in California

Recap of Huanglongbing Cases in California

News Release

Huanglongbing has now been confirmed in numerous communities in Los Angeles and Orange counties. These detections are disheartening, but the Citrus Pest & Disease Prevention Program, California Department of Food and Agriculture and county agricultural commissioners are taking aggressive steps to remove all diseased trees and educate homeowners about this critical threat to California citrus.

Here is a recap of the Huanglongbing activity in California to date:

Hacienda Heights:

HLB+ Trees = 2

HLB+ ACP = 1 (on the initial HLB detection site)

San Gabriel:

HLB+ Trees = 56

HLB+ ACP = 4 (on HLB+ tree sites)


HLB+ Trees = 2

HLB+ ACP = 2 (1 on HLB+ tree site, 1 on a separate site)


HLB+ Trees = 0

HLB+ ACP = 1

La Puente:

HLB+ Trees = 0

HLB+ ACP = 1

La Habra:

HLB+ Trees = 1

HLB+ ACP = 0


HLB+ Trees = 11

HLB+ ACP = 8 (6 on HLB+ tree sites, 2 on separate sites)


HLB+ Trees = HLB+ ACP = 1 (1 on HLB+ tree site)

In response to each and every HLB positive tree detection, CDFA conducts mandatory 800-meter response, which includes surveys and sampling of all host trees, treatments and removal of the confirmed HLB infected tree.

Nursery stock in quarantine areas is placed under USDA-approved screen facilities, where it is held and tested for two years, or it is destroyed. Outreach is done to homeowners and elected officials to educate them on the severity of the issue encourage them to help stop the spread of this devastating disease.

2021-05-12T11:00:45-07:00June 26th, 2017|
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