Citrus Growers’ Response To Huanglongbing

Industry Committee Endorses Voluntary Best Practices

News Release

To provide California citrus growers with a strong toolbox of science-supported strategies and tactics to protect their orchards from Huanglongbing (HLB), the Citrus Pest & Disease Prevention Committee endorsed a set of best practices for growers to voluntarily employ in response to HLB in California.

Adult Asian citrus psyllid, Huanglongbing
Adult Asian citrus psyllid (Photo by J. Lewis). Courtesy of Citrus Research Board

The recommendations—which were developed based on a grower’s proximity to an HLB detection—represent the most effective tools known to the citrus industry at this time and are meant to supplement the California Department of Food and Agriculture’s required regulatory response. The best practices were developed by a task force consisting of growers from various regions across the state and scientists, all of whom were nominated by the Citrus Pest & Disease Prevention Committee.

Voluntary best practices were developed for growers in the four following scenarios:

  • Scenario 1: Orchards outside of an HLB quarantine area
  • Scenario 2: Orchards located between one and five miles of an HLB detection (within an HLB quarantine area)
  • Scenario 3: Orchards within one mile of an HLB detection but not known to be infected
  • Scenario 4: Orchards with HLB

The best practices vary in each scenario but all address: awareness, scouting for the Asian citrus psyllid, controlling Asian citrus psyllids with treatments, protecting young trees and replants, employing barriers or repellents, visually surveying for HLB, testing psyllid and plant material for HLB using a direct testing method like polymerase chain reaction (PCR), and tending to trees’ root health. The voluntary best practices in all four scenarios can be found at CitrusInsider.org.

While HLB has not yet been detected in a commercial grove in California, the disease continues to spread throughout residential communities of Los Angeles, Orange, and Riverside counties. HLB has infected more than 1,400 citrus trees, and 1,003 square miles are currently in an HLB quarantine area.

“Our state’s citrus industry has held the line against HLB since the first detection seven years ago. We should commend our efforts but must not forget the devastating impact HLB could have on our orchards and our livelihood,” said Jim Gorden, chair of the Citrus Pest & Disease Prevention Program and a citrus grower in Tulare County.

“We know the cost to manage the Asian citrus psyllid is far less than any potential costs or loss to the industry should HLB take hold throughout our state. These voluntary best practices are meant to serve as a box of tools so growers can use as many as are feasible for their operation in order to limit the spread of the psyllid and disease,” said Keith Watkins, chair of the task force that developed the best practices and vice president of farming at Bee Sweet Citrus.

Reducing ACP Spread In California

Beth Grafton-Cardwell: Spread of Disease Must Be Prevented

By Patrick Cavanaugh, Editor

Collaborative changes are being made to combat the Asian Citrus Psyllid (ACP). Beth Grafton-Cardwell is the director of Lindcove Research and Extension Center near Exeter, as well as a research entomologist with UC Riverside. She recently spoke at the 2019 Citrus Showcase in Visalia as a key speaker on the state of Huanglongbing (HLB) in California, with an overview of how to prevent ACP,—which vectors HLB, a fatal disease to citrus—from moving around the state.

We were trying to communicate why we’ve made the changes we’ve made for the industry that has been a collaborative effort between CDFA, growers, and the university, Grafton-Cardwell said. “We need better ways to prevent psyllids from moving around the state because they might have HLB in their bodies, and we’ve got to prevent the spread of the disease.

beth_grafton-cardwell
Beth Grafton-Cardwell

The Florida citrus industry did not do a great job in containing the Psyllid, and now HLB is rampant in the state’s citrus industry, which has devastated the citrus economy there.

“Florida found that they did not do much to control psyllid movement, and they found that psyllids were moving in bulk citrus bins and retail nursery plants around the state, and within a concise amount of time, they spread the Psyllid and the disease everywhere,” Grafton-Cardwell said. “We’re trying to avoid that. We have 100% tarping of citrus truckloads. We have treatments that have to be done if growers want to move citrus between major zones in California, so that we can prevent that kind of movement.”

Conversations continue about quarantine areas in California to reduce spread.

“There’s been a lot of discussion regarding quarantines because it’s painful for some growers who have low Psyllid numbers to have to treat and to move their fruit to other zones.”

“There’s been a lot of questions. We did a lot of scientific analysis to look at impacts as well as numbers. It’s not just about psyllid numbers; it’s about their impact if growers were to move the disease into a high citrus growing region,” Grafton-Cardwell explained.

Quarantines in Place to Prevent ACP Spread

Quarantines Painful For Some Growers

By Mikenzi Meyers, Associate Editor

It’s been a tough road for citrus growers since the discovery of the Asian Citrus Psyllid (ACP) back in 2012. Those affected have been forced to quarantine their crops, a task that Beth Grafton-Cardwell, director of Lindcove Research Extension Center in Tulare and research entomologist with UC Riverdale, said can be difficult.

“There’s been a lot of discussion about the quarantines because they’ve been painful for some growers who have low psyllid numbers to have to treat them and move their fruit to other zones,” Cardwell explained.

Beth Grafton-Cardwell

The growing concerns have led to continuous research regarding whether or not the zones should be changed.

There have been more than 1,100 citrus trees that have tested positive for HLB. There have been more than 230 positive finds of the psyllid, and although this sounds like a big number, Cardwell said its actually normal due to how difficult the disease is to detect.

“We can’t tell that the tree is infected early on because a localized infection might be on one stem of the entire tree, and it might take a year before it moves throughout the tree,” she said.

Right now, quadrant sampling is being done, where four quadrants of the tree are sampled for the disease. Current samples are showing that one in four quadrants are coming back positive.

“It’s finding the trees that are infected that’s really difficult, and meanwhile, the psyllid is spreading, spreading, spreading the disease,” Cardwell said.

 

More information can be found at this link:

https://maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf

Preventing the Spread of ACP

Valley Citrus Growers Continue Vigilance

By Jessica Theisman, Associate Editor
ACP
USDA ACP Cooperative Program Map (Source:
California Citrus Pest & Disease Prevention Program)

The spread of Asian Citrus Psyllid (ACP) continues to be a looming threat for Central Valley citrus growers as it vectors Huanglongbing (HLB), a disease that destroys citrus trees. Greg Douhan, a University of California Cooperative Extension Tulare County citrus farm advisor reported to California Ag Today recently that, “There have been so many people onboard really working at this from multiple angles, and we’re in the eradication mode. We want to make sure the insect doesn’t get established in the San Joaquin Valley.”

“If one were to look at a map of ACP infestation in California [such as CDFA Quarantine Maps and California Citrus Pest & Disease Prevention Program Threat map], they may consider it to be endemic in the Los Angeles area. Rest assured that anytime ACP is found in a trap, the CDFA sprays everything in that area within 400 meters.”

Douhan said the Valley is on high alert to find ACP in traps. “

If researchers discover a cluster of finds in any particular area, we manage some spray programs and try to get all the growers to do a coordinated effort in order to try to combat it,” he said.

SaveOurCitrusIn addition, the SAVE OUR CITRUS app is a free USDA iPhone app to report and identify the four leading citrus diseases: citrus greening, citrus canker, citrus black spot and sweet orange scab. Report your symptoms, upload a photo, and citrus experts will respond.

So far, the practices have been working well.

“I think most of the growers are very well informed,” Douhan said, “and are taking this very seriously because it is this their livelihood.”

Fighting Asian Citrus Psyllid On and Off the Farm

Fighting ACP on Farms and Residential Areas Critical

By Hannah Young, Associate Editor

Pests and diseases are as prominent as ever not only for California farmers but in residential areas as well. California Ag Today recently spoke with Rick Westcott, a senior sales rep for Bayer Crop Science, about preventative materials for pests and diseases and the importance of controlling the spread of those diseases, particularly Asian citrus psyllid.

Westcott explained that the advantage of Movento, a powerful insecticide, is that it is systemic, it’s applied early, and it will translocate throughout the entire tree.

“It’s both phloem and xylem movement, so it’ll go down into the roots and then back up so it constantly recirculates within the plant,” Westcott said. “That’s what gives it the longevity of control.”

In citrus trees, Movento typically takes about 65 to 70 days to start working after circulating through the plant which helps with the longevity of the product, Westcott added.

Although Movento is not used specifically for Asian citrus psyllid, it has proved to aid in controlling the pest.

Westcott said Movento is currently being used against citrus red scale and applied during pedal fall along with thrip sprays, which farmers are applying anyway.

“It will take care of your red scale, your early red scale spray, and of course, because it also controls Asian citrus psyllid, it’s a bonus to do that too,” Westcott said. “Then the other thing that they’re doing with the thrip spray as well for katydid control, which is also an issue in citrus at that thrip timing.”

By patrolling and monitoring for ACP, the spread of HLB can also be controlled.

“The key is to keep the ACP at the lowest level possible or zero if that’s possible. [The] fortunate thing for us in the San Joaquin Valley is the fact that we do a lot of spraying for other pests throughout the year that almost everything that we put in the tank happens to also control ACP at the same time,” Westcott explained.

Westcott said that this is the reason we have not seen a huge outbreak of ACP in the San Joaquin Valley, unlike other parts of California.

“The problem isn’t in any commercial grove at this point, but it’s all residential,” Westcott continued. “It’s all concentrated in the residential areas, so there are certain products that you can use an ag that you can’t use there, but most of them, fortunately, you know, they have a label for both residential and agriculture, so they do crossover to stop them there so they don’t get here.”

HLB is still posing a threat in California, but most specifically in the Los Angeles area.

“The total amount of trees currently that are infective with HLB in the counties of LA, Orange and Riverside County is 645. And then if you compare that from a year ago: a year ago, there were only 73 trees that they had infected, and it’s changing every day,” Westcott said.

ACP Spread in Bakersfield Area, Ingenious Research Proceeds

Ingenious Research Effort to Fight ACP Spread with Natural Predators

 

By Joanne Lui, Associate Editor

 

beth_grafton-cardwell
Beth Grafton-Cardwell, Cooperative Extension specialist, University of California, Riverside Department of Entomology

As we have reported in-depth before on California Ag Today, the Asian Citrus Psyllid (ACP) is a tiny, mottled brown insect that poses an ever-increasing threat to the state’s robust citrus industry, as well as to residential citrus trees. The pest can spread a bacterium known as Huanglongbing (HLP) that is fatal to citrus trees. The disease has nearly shut down Florida’s citrus industry.

Beth Grafton-Cardwell, cooperative extension specialist in integrated pest management, UC Riverside Department of Entomology, explained the significance of the recent ACP spread to Bakersfield. “That is really problematic because it’s mostly in the urban areas. It’s very difficult to find, to control and to stop that spread. It’s going to move out from that region into the local citrus orchards, and so there are lots of meetings and discussions right now to mobilize growers to get treatments to help protect their citrus orchards against the psyllid.”

#CitrusMatters
#CitrusMatters

To contain the ACP problem, Grafton-Cardwell stated, “There are traps everywhere, but the traps are not terribly efficient. So, we really need to carefully examine groves and flush [new leaf growth] for the nymph form,” she said.

According to Agriculture and Natural Resources, University of California’s Statewide Integrated Pest Management Program:

Adults typically live one to two months. Females lay tiny yellow-orange almond-shaped eggs in the folds of the newly developing “feather flush” leaves of citrus. Each female can lay several hundred eggs during her lifespan.

ACP UC IPM
ACP (Source: ACP UC IPM)

The eggs hatch into nymphs that are wingless, flattened, yellow or orange to brownish, and 1/100 to 1/14 inch long. Nymphs molt four times, increasing in size with each nymphal stage (instar), before maturing into adult psyllids. The nymphs can feed only on soft, young leaf tissue and are found on immature leaves and stems of flush growth on citrus.

Save Our CitrusThe nymphs remove sap from plant tissue when they feed and excrete a large quantity of sugary liquid (honeydew). Each nymph also produces a waxy tubule from its rear end to help clear the sugary waste product away from its body. The tubule’s shape—a curly tube with a bulb at the end—is unique to the Asian citrus psyllid and can be used to identify the insect.

Grafton-Cardwell and other experts are concerned because once the ACP becomes established in urban areas, it is difficult to eradicate. “It starts spreading into the commercial citrus, and we’re off and running,” she commented.

bayer-save-our-citrusIn a ingenious effort to control the spread of the psyllid, trained teams of entomologists have imported Tamarixia radiata, a tiny wasp that naturally preys on ACP, from Pakistan to research and release in California. A cooperative effort of the University of California Riverside, Citrus Research Board, United States Department of Agriculture and California Department of Food and Agriculture, researchers are also exploring the effectiveness of another beneficial insect called Diaphorencyrtus aligarhensis to assist Tamarixia with control of the Asian citrus psyllid. To see where Tamarixia and Diaphorencyrtus have been released, visit this University of California’s website map at, “Distribution of ACP, HLB and Parasites in California,” and turn on the parasite layers.
Grafton-Cardwell said, “They’re going to inundate that area,” with natural ACP predators, “so hopefully that will push back a little bit.”