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.

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Citrus Psyllid Control Strategy Changes

Reducing Sprays in Areas, and Border Nets

By Jessica Theisman, Associate Editor
beth_grafton-cardwell
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.”

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Huanglongbing is causing concern in California

Increase of Huanglongbing in California Causes Concern

 By Brian German, Associate Broadcaster

Southern California has seen a concerning increase in the amount of trees that are infected with Huanglongbing, or citrus greening disease. California Ag Today discussed the news with Beth Grafton-Cardwell, an IPM Specialist and Research Entomologist for the UC Riverside Entomology Department stationed in the San Joaquin Valley.  She agreed that there is an increased concern surrounding HLB.

“It kind of exploded this fall, and it’s kind of continuing. And, that’s not unexpected. The Department of Food and Ag removes only the trees that are polymerase chain reaction – positive. And sometimes, it takes one to two years for a tree for you to be able to detect the bacteria using that method,” Grafton-Cardwell said.

Beth Grafton-Cardwell

There is no cure currently available for HLB, so once a tree is infected, it will eventually die.  Researchers continue working to find a possible cure for HLB, or at the very least, a more effective means of diagnosing infected trees. “Most of the techniques that are going to help us cure or prevent the disease from being transmitted are five to ten years away. Yet, I think we’re going to see a rapid expansion of the disease in Southern California in this coming year,” Grafton-Cardwell said.

Early detection is one of the most important things.  Grafton-Cardwell noted that many farmers are “helping to get the research accomplished and, for example, helping to get early detection techniques tested, and things like that so that we can try and stay on top of the disease.”

In California, production trees are not required to be screened, but many nurseries are now shifting towards putting all of their trees under screening in an effort to be more proactive in guarding against the spread of HLB.

Biological controls like Tamarixia are used as a means to reduce the number Asian citrus psyllids, which cause HLB, but that type of control method is not designed to completely eradicate insects.

“They’re starting to release the Tamarixia Wasps in Bakersfield. So we’re getting them up into the San Joaquin Valley so they can help out in those urban areas,” Grafton-Cardwell said.

Dogs are also used as a means to detect infected trees, but there is still a need for more effective techniques.  “A large team of dogs can do maybe 1,000 acres a day, and we’ve got 300,000 acres of commercial citrus. So I think we need a multitude of techniques,” Grafton-Cardwell said.

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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.”

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Citrus Growers Form ACP Management Areas

Commercial Citrus Growers Form Local ACP Management Areas

By Charmayne Hefley, Associate Editor

 

Commercial citrus growers are banding together to prevent the spread of the citrus-deadly Huanglongbing (HLB) disease and the pest that spreads it—the Asian Citrus Pysllid (ACP). Beth Grafton-Cardwell, an IPM specialist and research entomologist at UC Riverside and Director of UC ANR Lindcove Research & Extension Center, said growers are forming ACP management areas to prevent ACP from spreading HLB.

Elizabeth E. Grafton-Cardwell
Elizabeth E. Grafton-Cardwell

“ACP management areas are being formed by the citrus industry and community,” Grafton-Cardwell said. “They’re basically saying, ‘Let’s get together. Let’s form these groups of growers—25 to 35 growers in an area. Let’s work together as neighbors to treat across a large area and get more of the psyllids killed than if we each treated individually at different times.’”

HLB is a serious concern to growers, according to Grafton-Cardwell; the disease has already devastated the citrus industry in Florida. “We want to prevent that from happening here,” shel said.

According to the California Department of Food and Agriculture, ACP notices posted thus far in the first quarter of 2016 include the following areas:

            COUNTY                                                                 CITY

   Fresno County    Fresno
   Kern County    Bakersfield, Shafter, Wasco
   Imperial County    Bard, Brawley area, Calipatria, Niland, Winterhaven, Zone 7
   Los Angeles County    La Puente, San Gabriel
   Riverside County    Hemet, Riverside, San Jacinto
   San Bernardino County    Cadiz
   San Diego County    De Luz, Escondido, Fallbrook, Ramona, San Diego
   San Joaquin County    Stockton
   Santa Barbara County    Areawide, Buellton, Casmalia, Garey, Orcutt, Santa Maria, Sisquoc
   Santa Clara County    Milpitas, San Jose
   Stanislaus County    Oakdale
   Tulare County    Porterville, Strathmore

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Red Scale Challenges Citrus

Besides HLB, Red Scale Challenges Citrus

By Charmayne Hefley, Associate Editor

While much of the talk in the citrus industry is about how to fend off Huanglongbing (HLB) disease, one of the most devastating citrus diseases, Dr. Beth Grafton-Cardwell, director of the University of California Agriculture and Natural Resources Lindcove Research and Extension Center, reinforced that HLB isn’t the only pest that can overtake California’s citrus orchards.

Grafton-Cardwell explained how last year’s warm winter led to an increase in the California red scale, Aonidiella aurantii, population. “Normally we have cold conditions that kill off the younger instars of the scales and [basically] restarts the system. But we didn’t really have any low temperatures last year, so the scales didn’t go into their usual hibernating phase. They just kept cranking out crawlers and adding in an extra generation or two of production. So the higher number of scales on the trees made it much more difficult for the growers to control.”

Grafton-Cardwell explained while it is difficult to speculate whether this coming year will yield another large population of the CaSave Our Citruslifornia red scale, “We have already received more moisture as a result of seasonal rainfall, which should help hinder the pest. Hopefully we’ll get some cooler weather conditions too–not freezing because citrus groves don’t like freezing temperatures–but cold enough to knock out some of the scales and get the population back under a manageable level,” she said.

Nevertheless, despite the challenges that California red scale can cause, Grafton-Cardwell said, overall, citrus growers need to keep their focus on the fight against the Asian Citrus Pysllid (ACP), Diaphorina citri, and its ability to spread HLB. “Growers need to start thinking in terms of: California has the [HLB] disease and it’s going to start spreading in southern California soon,” Grafton-Cardwell said. “What do we do to prevent it from spreading up here into the San Joaquin Valley?”

Photo source: “Life Stages of California Red Scale and Its Parasitoids,” UC ANR Publication #21529, by Forster, Lisa D.; Robert F. Luck; and Elizabeth E. Grafton-Cardwell; with photos by L. Forster and M. Badgley)

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TODAY’S MEETING IN FRESNO ADDRESSES ACP

Fresno County on Alert for ACP

 
Assemblyman Jim Patterson

Assemblyman Jim Patterson hosted the Citrus Industry Town Hall this morning at the Fresno County Farm Bureau office to discuss the current state of the Asian Citrus Psyllid presence in California, the quarantine situation, how Fresno County is preparing for the possible migration of ACP into the county, and how agencies, growers, and the state and federal governments are cooperating to control its spread in California.

Over forty people attended the meeting, including growers, PCAs, local government and industry leaders, researchers, and media.

Fresno County is the fourth largest citrus-producing county in California, having dropped in status due to freeze-damaged mandarin acreage last year, according to Les Wright, Fresno County Ag Commissioner.
Les Wright
“ACP spread is one of the most serious problems facing valley citrus growers especially those in the south valley,” said Wright.
 
To date, all contiguous counties in southern California are under CDFA Quarantine, as well the Porterville area of Tulare County, to prevent movement of ACP-ridden leaves and plant debris and unsanitary ag equipment into non-infested regions of the state and to bide time for agency mobilization and industry research to catch up. The effort also aims to prevent ACP from finding HLB-infected trees and spreading the incurable disease.
 
Though presently under quarantine, the effort in southern California to stop the spread of ACP, it was emphasized, was NOT a failure; rather, it bought precious time for other regions to prepare, and while many treatments did not work, other regions are learning from their attempts.
 
Creative Solutions
 
Dr. Beth Grafton-Cardwell

Dr. Beth Grafton-Cardwell, UC IPM Specialist and Research Entomologist, recently studied ACP found in Texas and Florida and reported that local agencies here are following Florida’s lead in organizing grower groups and local neighbors to treat their trees simultaneously.

She said that researchers are looking for natural processes, among others, to control ACP populations.
 
Victoria Hornbaker, CDFA, Program Coordinator, gave the example of Dr. Mark Hoddle, Extension Specialist and Director of the Center for Invasive Species Research at UC Riverside, who is working towards the massive release of Tamarixia radiata wasps, a natural predator of ACP, found in Pakistan. In studies of small releases of T. radiata, the wasps were found outside the areas where they were released—a good indication of their hardiness and potential effectiveness against ACP.

Victoria Hornbaker

While there is no cure for HLB thus far, researchers are looking at altering the ACP so it cannot pick up HLB disease, inserting a gene so it cannot carry HLB, and creating disease-resistant plants.

Organic insecticides against ACP are short-lived, so they must be applied more frequently than their conventional counterparts. Thus, organic farmers must be more aggressive in their treatments.
 
UC Davis is studying new efficacious organic products.
 
If an organic farm were in an eradication zone, the grower would be required to use conventional products, losing organic status for one year. Without compliance, the property would be abated.
 
It is recommended that when a grower sprays for a different pest, they should choose a product that also works on ACP.
 
Eradication and management strategies differ according to season.
 
Product spraying frequency and product choice are delicate decisions so as not to cause resistance in ACP.
 
Expert dog sniffers can detect the presence of ACP, and have detected infested shipments that were subsequently destroyed. California is vigilant at all points of entry including airports, border traffic, and ports. Not all counties have expert canines; however, Fresno has one such specialist. The USDA also provides dogs, one of which works in Fresno.
 
Take Action Now
 
Start sampling now.
 
Do not rely on (color-saturated) yellow-sticky traps for detection. Remember that psyllids are attracted to citrus trees, which have both color and scent.
ACP likes an orchard’s edges, so test for their presence around a field’s perimeter, as well as down the center for good measure.
 
Go to the following websites for information, quarantine maps, crop protection cost-effectiveness:
·       CDFAWebsite
In the event a homeowner or grower suspects ACP on their property, take the bug, if possible, put it in alcohol, and contact the Fresno County Farm Bureau; Sylvie Robillard, Fresno County Grower Liaison; the CDFA Hotline, 1-800-481-1899 or your local Ag commissioner (if outside Fresno County).
 
Joel Nelson
Joel Nelson, California Citrus Mutual, President, commented, “If it weren’t serious, it would be exciting” due to the talent of the people involved in the fight to suppress the ACP and thereby avoid HLB disaster in the state. With southern California producing $750,000 and the Central Valley producing $1.5 billion in citrus, California is the largest citrus-producing state in the country, providing 85% of the country’s fresh citrus.
 
Stopping the spread of ACP and eradicating Huanglongbing (HLB) is among the top five priorities of the USDA. The federal government has contributed $10 million to the California program toward that end.
 
A coalition of groups is conducting a public relations campaign starting in southern California that includes distribution of bookmarks and brochures (in several languages) that have a little magnifying glass inside to detect ACP; enlisting legislators and box stores, among others, to help spread information; and launching a PSA next week featuring Citrus Grower Kevin Severns speaking about this crucial situation.There are 6 versions of the PSA on CCM’s YouTube Channel.
 
Nelson emphasized that every step this coalition in California takes is globally unprecedented. And the government is flexible and ready to adopt new strategies; using this effort in California as a model for other programs planned to eradicate foreign invading pests.
 
Assemblyman Jim Patterson concluded by acknowledging, “Agriculture is more than a livelihood; it‘s a life.”