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.
Center director Jeff Dahlberg, who will be 108 years old in 2065, predicted in his letter that today's modern technology – smart phones and computers – will be ditched by then in favor of holographic demonstrations about new plants and agronomic practices.
“You'll be able to see, in 3-D, how plant systems function, how genes work, and what happens when you turn a gene off or on and the cascading effects of those actions,” Dahlberg predicted.
A time capsule containing the letters will be buried on May 26, exactly 50 years after the May 26, 1965, dedication of the sprawling research station near Parlier in the Central San Joaquin Valley. It will also contain a 20-foot-long banner with a timeline showing significant research accomplishments at Kearney. The banner will have signatures and messages from all the attendees at the 50th anniversary celebration on May 26, 2015.
Kearney is one of nine agricultural research and extension facilities UC Agriculture and Natural Resources maintains in California. The northernmost is on the Oregon border near Tulelake; the southernmost is in Holtville, a short drive from the border with Mexico. Centers are found in the Sierra foothills, in the North Coast and in suburban Southern California. Each center represents local conditions and focuses on crops and activities important in the area.
At the 330-acre UC Kearney Agricultural Research and Extension Center, scientists conduct research on a diversity of Central San Joaquin Valley crops, including grapes, stone fruit, almonds, pistachios, pomegranates, kiwi fruit, blueberries, alfalfa and more recently sorghum. Twenty Ph.D.-level scientists are based at the center, where they conduct research in pest control, new crop varieties, plant disease control and irrigation strategies.
A scientist who joined the staff in 2013, Kris Tollerup, UC ANR Cooperative Extension advisor with the UC Statewide Integrated Pest Management Program (IPM), will be looking for some answers from his successors.
“Growers and pest control advisors are reluctant to adopt new IPM practices until they are well proven,” Tollerup wrote. “I am curious, do you face the same challenge?”
Since Tollerup will be 105 when the time capsule is opened, his young children, who will be 54 and 58 in 2065, may have to collect the responses for him.
UC IPM advisor Pete Goodell, who with 34 years of service to UC ANR is approaching retirement, had sage advice for successors that might continue to be bombarded with modern conveniences.
“My advice,” Goodell wrote. “Get out of the office and get to the farm . . . Create and nourish human networks as well as virtual ones.”
Goodell tells his successors that, no matter the technological advances that are sure to come, knowledge transfer will always be based on personal contact and trust.
“Humans, even in your time, are high touch species who thrive on social interaction,” he said.
The other three letters going in the time capsule include these quotes:
“I assume that (nematodes) still will be around when you read this letter. At least this is something that I tell my students: ‘nematode problems will outlive us.'” – Andreas Westphal, UC ANR Cooperative Extension nematology specialist.
“Release of genetically modified mosquitoes carrying sex lethal genes has been approved on a relatively small scale in a few countries. I wonder if this method of control will be better perceived in the future and become the norm?” – Anthony Cornel, entomologist and director of the Mosquito Lab at Kearney.
“It will be interesting to see how the citrus industry adapts to the (Asian citrus psyllid/huanglongbing) situation. Growers are very creative people and I believe they will find a way.” – Beth Grafton-Cardwell, UC ANR Cooperative Extension entomology specialist.
Author: Jeannette Warnert
The site’s launch coincides with the announcement last month by the California Department of Food and Agriculture that six more psyllids were found in three Tulare County yellow sticky traps. In 2012, three psyllids were found on two traps and an eradication program ensued.
The new website was developed by Beth Grafton-Cardwell and Matt Daugherty, UCCE specialists in the Department of Entomology at UC Riverside, Karen Jetter, economist with the UC Agricultural Issues Center, and Robert Johnson programmer with the UC Agriculture and Natural Resources Informatics and GIS Statewide Program program. Funding for the site was provided by UC Agriculture and Natural Resources.
The website includes information on the psyllid's distribution in California, monitoring methods and treatment options. For example, the website suggests citrus farmers and homeowners not rely on yellow stick card traps to monitor for the pest.
“At certain times of the year, the yellow sticky cards are totally unattractive to Asian citrus psyllid,” Grafton-Cardwell said. “The cards are just color, but citrus flush is an attractive color and also emits irresistible volatiles or smells.”
The website advises farmers to regularly conduct systematic visual surveys along the margins of their orchards looking carefully at new green shoots and conducting tap sampling. To tap sample, spray a plastic surface with soapy water, position the plastic sheet underneath a branch and tap the branch above to dislodge adult ACP. The insects will stick to the filmy plastic where they can be studied with a magnifying hand lens to determine if they are psyllids.
If psyllids are found, the UC website outlines the immediate action that is required.
Adult psyllids should be placed in a container with 90 percent alcohol and reported to the county agricultural commissioner’s office so the insects can be tested for huanglongbing disease. Immature stages of the pest should be left on the tree so the ag commissioner’s office can make an official regulatory collection.
“Florida and Texas don’t have exactly the same insecticides that are available in California and the environmental conditions are different,” Grafton-Cardwell said. “Over time we will compare different treatments and determine how long they will protect the trees. Any new developments will be posted to the website.”
Because the goal in the San Joaquin Valley is eradication, Grafton-Cardwell recommends aggressive action against a psyllid infestation.
“The best approach is using two broad-spectrum insecticides within a short period of time,” she said. “No one insecticide will kill all the stages of the pest."
Another key to successful eradication is area-wide treatment coordination. Grafton-Cardwell suggests farmers work closely with their treatment liaisons and treat their orchards in a coordinated manner.
“The bigger the area being sprayed at the same time, the better,” Grafton Cardwell said. “If we get a blanket effect over the whole area, that’s been shown in Florida and Texas to have the greatest impact on the psyllid populations.”
The aggressive psyllid treatment aims to buy time for researchers to find long-term strategies for maintaining the California citrus industry in the presence of ACP and, especially, with the incurable and fatal citrus disease they spread, huanglongbing.
The July ACP find prompted the California Department of Food and Agriculture to quarantine 178 square miles in the Porterville area, placing severe restrictions on the movement of local citrus nursery stock and citrus fruit outside the area. It also prompted several hundred farmers and pest control advisers to gather July 30 at the International Agri-Center in Tulare for an update on the threat.
Like a scene from the film “Scared Straight,” Ken Keck, former executive director of the Florida Department of Citrus and now director of the California Citrus Research Board, admonished the California farmers to learn from the Sunshine State’s mistakes.
“I feel like the ex-con in front of a room of 17-year-olds,” Keck said. “All I can say is, ‘prevent, prevent, prevent.’”
Asian citrus psyllid is established in Southern California. Efforts in the southern part of the state are focused on managing the psyllids to reduce the likelihood they will find a tree infected with huanglongbing. Huanglongbing (HLB) is an incurable and fatal disease of citrus spread by ACP.
By working together and following science-based treatment strategies, UC Cooperative Extension specialist Beth Grafton-Cardwell believes farmers and CDFA can still eliminate ACP in the San Joaquin Valley, where the bulk of the state’s commercial citrus is grown.
At the Tulare meeting, Grafton-Cardwell explained the eradication strategy she developed by studying Asian citrus psyllid and huanglongbing disease management programs in Florida and Texas, another state where the pest is well established.
“We want to slow the spread of psyllid into new areas,” Grafton-Cardwell said. “We want to prevent psyllids from finding HLB infected trees.”
Although it is unlikely the pest and disease can be kept at bay indefinitely, Grafton-Cardwell said the battle will buy time for researchers to discover long-term approaches for maintaining California’s citrus industry in the presence of ACP and HLB.
Developing citrus varieties resistant to HLB through traditional breeding or genetic modification will take too long, she said. Scientists are considering such futuristic solutions as inserting HLB resistance into a mild form of the Tristeza virus and inoculating trees with the virus to fight HLB.
“Everyone is racing to come up with tactics to fight ACP and HLB,” she said. “I believe we will eventually be using multiple approaches, such as a repellent spray to keep ACP off the trees and perhaps breeding ACP that can’t transmit HLB and then flooding the population with these incapacitated psyllids.”
To fight ACP and HLB, growers and homeowners can access detailed information on the pest’s distribution, monitoring methods and treatment options on a new website created by Grafton-Cardwell with funding from UC Agriculture and Natural Resources.
For tap sampling, spray a plastic surface with
The website advises farmers and homeowners to regularly conduct visual surveys and tap sampling (see video on right) in their orchards. “Yellow sticky card traps are not very attractive to psyllids,” it says.
If psyllids are found, immediate action is required.
Adult psyllids should be placed in a container with 90% alcohol and reported to the county agricultural commissioner’s office so the insect can be tested for HLB. Immature stages of the pest should be left on the tree so the ag commissioner’s office can make an official regulatory collection.
An ACP find should also trigger rapid and wide treatment with the most effective pesticides possible.
- Posted By: Jeannette E. Warnert
- Written by: Jeannette Warnert, (559) 646-6074, firstname.lastname@example.org
Typical fruit grading equipment determines fruit size, count and grade. The Compac InVision 5000c has three lighting systems – fluorescent, ultraviolet and near infrared – plus a weigh bridge that together measure fruit dimensions, weight, color, and blemishes from insect damage, scarring and sunburn. Without spoiling the fruit, the grader also determines its sweetness and assesses internal damage. The new line can handle citrus fruit sizes ranging from a small mandarin up to a grapefruit.
“This equipment will give our researchers much more precise information for making comparisons,” said Beth Grafton-Cardwell, director of the Lindcove REC. “Our old packing line could tell us an overall color of the fruit. The Compac grader precisely defines how much of the surface area is green, yellow and orange.”
Highly advanced software works in conjunction with the equipment, recording measurements and a series of photographs – color and ultraviolet – for each individual fruit, allowing scientists to run correlations between all the parameters.
“We can determine which rootstock and scion combinations give the perfect size, sweetest taste and best ripening fruit,” Grafton-Cardwell said. “We will be able to train the software to recognize various types of pest damage – such as damage from katydids and citrus peelminer – and demonstrate which pesticides best protect the fruit from damage.”
In the past, labor costs limited researchers to gathering such detailed information from only a small sample of fruit on certain trees. With the new Compac grader, all the fruit from particular trees can be thoroughly assessed.
Another benefit of the upgraded equipment is its light-touch. The machine can gather data about mandarin oranges without harming the delicate peel. Growing interest in mandarins has UC scientists devoting more time and resources to the diminutive fruit. While Valencia and navel orange acreage is holding steady or dropping in California, mandarin acreage has tripled in the last 10 years.
“As the Valencia market has declined, many Valencia orchards are being replaced with mandarins,” Grafton-Cardwell said. “We have dozens of excellent varieties of mandarins and consumers love them because they’re easy to peel. Mandarins are the wave of the future.”
The cost of the Compac fruit grader was covered by the Citrus Research Board, a grower-funded organization created to support citrus research.
“The new fruit grader is another example of the excellent collaborative relationship the University has with the citrus industry,” Grafton-Cardwell said.
See the components of the new fruit grading system in the video below: