- Author: Ben Faber
Citrus greening disease, also called huanglongbing (HLB), is a bacterial infection of citrus trees that results in small, misshapen and sour fruits that are unsuitable for consumption. The disease ultimately kills the tree.
Because there is no cure, HLB is a major threat to the $10 billion citrus industry in Florida, where it was first detected in 2005,and to the $7 billion industry in California, where it appeared last year.
Researchers from the Boyce Thompson Institute (BTI), the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) and the University of Washington investigated a seemingly unlikely source of biocontrols for HLB: neuropeptides found in Asian citrus psyllids, the insect that carries the disease-causing bacterium Candidatus Liberibacter asiaticus (CLas), which it spreads while feeding on a tree's leaves and stems.
The research team, led by BTI faculty member Michelle Heck, published its findings on Feb. 10 in the Journal of Proteome Research.
Laura Fleites, a research associate in Heck's group at BTI, focused on neuropeptides because they function as hormones in hemipteran insects – a class that includes psyllids, aphids, whiteflies, shield bugs and other crop-plaguing species – to regulate growth, development and other biological functions.
“If we could develop an insecticide that is specific for Asian citrus psyllids based on one of the insect's own neuropeptides, then we could protect citrus trees from the insect that spreads CLas,” said Heck, a USDA-ARS research molecular biologist and an adjunct associate professor in the School of Integrative Plant Science, in the College of Agriculture and Life Sciences. “Citrus greening disease is devastating our citrus industry, and we need to develop new ways for our citrus growers to control it.”
Fleites and the team characterized the full array of peptides found in the psyllids and identified 122 potential neuropeptides. While promising, the findings offer only potential starting points for combatting HLB, because unmodified insect-derived neuropeptides are not suited for use as insecticides in the citrus grove.
To turn the findings into a usable product, the team is now part of a collaboration aimed at identifying the best psyllid-derived neuropeptide for development. The team will then stabilize the peptide and decide the optimum method for delivering the insecticidal molecule to citrus trees – whether as a spray, by engineering trees to make the peptides themselves, or by some other method.
For the study, Fleites developed new extraction and analysis methods other researchers could use in their investigations of insect peptides.
“Thanks to USDA support, I was able to develop techniques that enable the identification of small, functional insect peptides separately from their larger, inactive precursors,” Fleites said. “Because these techniques aren't specific to psyllids, they may be useful for identifying neuropeptides in other hemipteran insects to protect crop plants.”
Heck said this work shows how USDA grant programs can be used to fund everything from discovery to product development. The neuropeptide discovery was done in a study funded by the National Institute of Food and Agriculture; the translational research is being done under a grant from the Animal and Plant Health Inspection Service.
Funding for this work came from a USDA Specialty Crops Grant and from the USDA-ARS.
Michael J. Haas is a freelance writer for the Boyce Thompson Institute.
https://news.cornell.edu/stories/2020/04/psyllid-peptides-could-fight-citrus-greening-disease
Asian citrus psyllids feed on a citrus tree. The psyllids deposit a bacterium in the sap that causes citrus greening disease, a scourge to the citrus industries in Florida and California, worth a combined $17 billion.
- Author: Ben Faber
Citrus greening, also called Huanglongbing (HLB), is devastating the citrus industry. Florida alone has experienced a 50 to 75 percent reduction in citrus production. There are no resistant varieties of citrus available and limited disease control measures.
Some scientists think it is possible that orange juice could one day become as expensive and rare as caviar. In an effort to prevent this, three plant pathologists at the University of California-Berkeley and United States Department of Agriculture conducted research into ways to boost citrus immunity and protect the valuable fruit against citrus greening.
Because the bacteria that causes citrus greening cannot be grown in a lab, scientists have to find novel ways to conduct experiments. The University of California-Berkeley/USDA team looked at many different strains of the bacteria that cause citrus greening to see if they could identify peptides (a compound of two or more amino acids) that would trigger immune responses.
"This was a long list, so we narrowed it down by selecting small peptides that were a bit different in their peptide sequence, which might imply that the bacterium had made those sequence changes so that they wouldn't be recognized by the plant immune system," explained Jennifer D. Lewis, group leader of the research team. "Then we further narrowed that list to peptides from strains that caused disease in citrus."
Through this research, they showed that two peptides could trigger immune responses in multiple plant species, including citrus. These peptides may play a role in preventing or reducing yield loss from citrus greening.
According to Lewis, "We thought it was particularly interesting that some of the peptides predicted to elicit a response, could actually trigger immune responses in multiple plant species. This suggests that the immune response to these peptides is conserved across species."
Ashley Bergman Carlin
acarlin@scisoc.org
651-994-3832
@plantdisease
- Author: Ben Faber
The USDA has released their Fruit and Nuts Outlook Report which shows the forecast the 2019/2020 seasons and provides an overview of the markets.
The 2019/20 citrus crop is forecast to be 7.63 million tons, down 4 percent from the previous season. Declines in overall production can mostly be attributed to smaller lemon, tangerine, and mandarin crops in California. Orange production in California has remained stable since last season. Citrus production in Florida has also remained stable with a 1 percent decline in orange production, and significant increases in grapefruit, tangerine, mandarin, and tangelo production over last year. Overall decreases in production of lemons, tangerines, mandarins, and tangelos are expected to result in increased imports, and higher prices compared with last year.
Fruit and tree nut grower prices began 2020 at low levels. At 117.8 (2011=100), the January 2020 index was down 10 percent from the January 2019 index and below the January average for 2016-18 (fig.1). The January 2020 index was the lowest since January 2013. Significantly lower grower prices for citrus fruit and apples drove down the index (table 1).
As of mid-March 2020, U.S. citrus exports were down except for orange juice and tangerines. Reduced exports have increased the domestic supply of citrus, putting downward pressure on prices. The January 2020 price of all- grapefruit is down 36 percent from the year before, and all-oranges and oranges for the fresh market are down by 6.9 and 9.4 percent respectively. All- lemon prices are down 28.5 percent, and fresh lemons prices are down by 8.6 percent.
Apple prices were down 21 percent in January 2020 from the year before. USDA, National Agricultural Statistics Service (NASS) estimates the 2019 total apple crop to be up 3.6 percent from 2018. The strong dollar and increased tariffs in several countries have reduced exports, putting downward pressure on prices.
- Author: Ben Faber
Dr. Elizabeth Grafton-Cardwell will discuss the key stages of citricola scale and how they damage citrus, weather trends that help reduce citricola scale, chemical control choices and their relative efficacy, coverage and timing of treatments, and monitoring for resistance and methods to manage resistance.
April 8, 2020, 3 PM
This is part of the series of 1-hour webinars, designed for growers and Pest Control Advisers, will highlight various pest management and horticultural topics for citrus and avocados. During each session, a UC Expert on the subject will make a presentation and entertain write-in questions via chat during and/or after the presentation.
What Are the UC Ag Experts Talking About?
Upcoming topics:
- Invasive shot hole borers in avocado by Akif Eskalen (May 2020)
- Vertebrate pests by Roger Baldwin (June 2020)
- Ants in citrus by Mark Hoddle (July 2020)
- Use of plant growth regulators on citrus by Ashraf El-kereamy (August 2020)
Register for the Citricola Scale webinar (April 8, 2020)
/span>/h1>
- Author: Ben Faber
New technique has potential
to protect citrus from HLB
Citrus greening, also called Huanglongbing (HLB), is devastating the citrus industry. Florida alone has experienced a 50 to 75 percent reduction in citrus production. There are no resistant varieties of citrus available and limited disease control measures.
Some scientists think it is possible that orange juice could one day become as expensive and rare as caviar. In an effort to prevent this, three plant pathologists at the University of California-Berkeley and United States Department of Agriculture conducted research into ways to boost citrus immunity and protect the valuable fruit against citrus greening.
Because the bacteria that causes citrus greening cannot be grown in a lab, scientists have to find novel ways to conduct experiments. The University of California-Berkeley/USDA team looked at many different strains of the bacteria that cause citrus greening to see if they could identify peptides (a compound of two or more amino acids) that would trigger immune responses.
"This was a long list, so we narrowed it down by selecting small peptides that were a bit different in their peptide sequence, which might imply that the bacterium had made those sequence changes so that they wouldn't be recognized by the plant immune system," explained Jennifer D. Lewis, group leader of the research team. "Then we further narrowed that list to peptides from strains that caused disease in citrus."
Through this research, they showed that two peptides could trigger immune responses in multiple plant species, including citrus. These peptides may play a role in preventing or reducing yield loss from citrus greening.
According to Lewis, "We thought it was particularly interesting that some of the peptides predicted to elicit a response, could actually trigger immune responses in multiple plant species. This suggests that the immune response to these peptides is conserved across species."
/h1>/h1>