- Author: Ben Faber
PULLMAN, Wash. – Washington State University researchers have for the first time grown the bacteria in a laboratory that causes Citrus Greening Disease, considered the world's most harmful citrus disease.
Being able to grow the elusive and poorly understood bacterium, Candidatus Liberibacter asiaticus (CLas), will make it easier for researchers to find treatments for the disease that has destroyed millions of acres of orange, grapefruit and lemon groves around the world and has devastated the citrus industry in Florida.
The researchers, including Phuc Ha, postdoctoral research associate, Haluk Beyenal, Paul Hohenschuh Professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, David Gang and Ruifeng He, from WSU's Institute of Biological Chemistry, Anders Omsland, from the Paul G. Allen School for Global Animal Health, and researchers from the University of Florida and University of Arizona, report on their work in the journal, Biofilm.
WSU was selected three years ago for a $2 million U.S. Department of Agriculture grant to study the bacteria, in part, because Washington has no citrus industry. The disease, formally known as Huánglóngbìng, (HLB), is spread by Asian citrus psyllids insects. It attacks the vascular system of citrus trees and causes fruit to become green, misshapen, and bitter-tasting.
A critical step in coming up with weapons to fight the disease is being able to study it in the lab, but the CLas bacterium is notoriously difficult to grow. With a small genome, CLas is thought to depend on very specific nutrient availability and possibly compounds secreted by other nearby bacteria. When researchers used a traditional rich media that they typically use for growing bacteria, they mostly grew bacteria other than CLas.
So, in order to conduct research, scientists have had to get bacterial samples directly from the trees themselves or from the insects that spread it, which is time-consuming and cumbersome. Trying to conduct experiments has also been difficult because, unlike neat lab cultures, bacterial samples gathered from a sick tree vary, depending on where and when the sample is gathered and the level of infection.
Without being able to grow the bacteria in a lab, researchers have been unable to even absolutely confirm that the bacteria, in fact, causes the disease.
In their paper, the researchers for the first time successfully established and maintained CLas bacterial cultures outside of its host.
Using infected citrus tissue as their starting point, the researchers developed a biofilm, a kind of bacterial city that allows a variety of bacteria to thrive. Instead of a rich growth medium that would crowd out the CLas, the researchers severely limited the growth of partner bacteria and created a medium with the specific nutrients, acidity, incubation temperatures, and oxygen levels that are optimal for CLas.
The CLas thrived – an important first step.
“We were really excited,” said Beyenal, “but then we wondered if we could re-grow it.”
The researchers were able to transfer the orange-colored culture and grow new cultures in their biofilm reactors, which they have maintained for more than two years.
“We can do this for as long as we want,” said Beyenal.
Beyenal's group is now working to purify the culture, which will further help researchers to study it. They are also developing genetic-based methods to understand and mitigate the spread of the disease.
Media contacts:
- Haluk Beyenal, Hohenschuh Distinguished Professor, Gene and Linda Voiland School of Chemical Engineering and Bioengineering, 509-335-6607, beyenal@wsu.edu.
- David Gang, Professor, Institute of Biological Chemistry, 509-335-0550, gangd@wsu.edu
- Tina Hilding, communications director, Voiland College of Engineering and Architecture, 509-335-5095, thilding@wsu.edu
Photo: Phuc Ha and Haluk Beyenal examine a bacterial culture in the laboratory.
- Author: Ben Faber
The USDA has summarized the US citrus crop for 2018-19 and it is up for both California and Florida, with CA accounting for 51% of US production! But the Florida orange crop is up from last year. This is the state that is getting hammered by huanglongbing amongst all the other demands being made on that industry. This is good news for citrus.
The full report is Here
But the summary is:
Citrus utilized production for the 2018-19 season totaled 7.94 million tons, up 31 percent from the 2017-18 season. California accounted for 51 percent of total United States citrus production; Florida totaled 44 percent, and Texas and Arizona produced the remaining 5 percent.
Florida's orange production, at 71.8 million boxes, is up 59 percent from the previous season.Grapefruit utilization in Florida, at 4.51 million boxes, is up 16 percent from last season's utilization. Florida's total citrus utilization increased 56 percent from the previous season. Bearing citrus acreage, at 387,100 acres, is 13,800 acres below the 2017-18 season.
Utilized citrus production in California increased 15 percent from the 2017-18 season. California's all orange production, at 49.8 million boxes, is 13 percent higher than the previous season. Grapefruit production is down 16 percent from the 2017-18 season but tangerine and mandarin production is up 35 percent. Utilized production of citrus in Texas is up 29 percent from the 2017-18 season. Orange production is up 33 percent from the previous season and grapefruit production increased 27 percent. Total citrus production in Arizona's lemon production is up 35 percent from last season.
The value of the 2018-19 United States citrus crop increased 1 percent from last season, to $3.35 billion (packing house-door equivalent). Orange value of production decreased 7 percent from last season and grapefruit value is down 1 percent.
Tangerine and mandarin value of production is 31 percent higher than last season but lemon value of production is down 4 percent.
Overall comparisons discussed above are based on similar fruit types. The revised production and utilization estimates are based on all data available at the end of the marketing season, including information from marketing orders, shipments, and processor records. Allowances are made for recorded local utilization and home use. Estimates for the 2018-19 California Valencia oranges and grapefruit are preliminary.
BUT, the latest news from the Central Valley navel forecast is that it is down,
The 2019-20 California navel crop is down 7% from last season, according to the first U.S. Department of Agriculture estimate.
With harvest expected to begin in October, the California navel forecast is 76 million (40-pound) cartons, down 7% percent from the previous year, the USDA said Sept. 12.
Farming is a roller coaster.
- Author: Ben Faber
Botryosphaeria Gummosis and Dieback
of Citrus
DeAnna Vega, M.S. Candidate, CSU-Pomona
Botryosphaeria dieback or Botryosphaeria gummosis (formerly known as Dothiorella gummosis on citrus), is found worldwide on many horticultural and agricultural crops. Multiple species of the fungus can often be found on a tree at any given time. Bot canker has a latent stage where it can exist within a tree for years without showing any symptoms. Most species are opportunistic, relying on plants to become stressed before it can infect the tree. The fungus can infect the scion, rootstock, and surface roots of a tree. Disease symptoms include; necrosis of the blossoms, shoots, and fruit. Botryosphaeria can lead to wilt, leaf lesions/spots, and fruit rot. Cankers along the stem, twigs, and branches are sunken necrotic (dead) areas with gum exuding from the bark. Transverse section (cross section) exposes wedged or irregular stained sections of infection ranging in color from gray to brown. Infected cambial wood can appear brown to yellowish in color. Extensive dieback, even mortality in extreme cases particularly with younger trees, can occur. Some unique characteristics of Botryosphaeria are black pustules (pycnidia – a type of fungal fruiting body) grouped together on the surfaces of or heavily infested bark.
Figure 1. Gummosis on blighted twig – red arrows pointing to gummosis exudates (A).
Canker with older exude (B). Blighted foliage and fruit (C). Botryosphaeria
sp. on fruit (D). Blighted twig (E). Photos courtesy of Ben Faber.
The pathogen favors warm weather from 20°C - 30°C (68°F - 86°F) and rainfall. When, temperatures rise above 10°C (50°F), spores are released to spread the disease in spring. In California, new year's infection typically starts in early April and the middle of spring (late May through June) from previously infected buds, where the disease had not fully developed. Infected buds produce shoots that are infected with the disease. The infected areas can become blighted within three to five days. Symptomatic leaves turn chlorotic (taking on a yellowish and sometimes mottled appearance), wilt, and becomes blighted along with the twig. Flagging (blighted and dead branches) occurs throughout the canopy where the disease has infected.
Figure 2. Flagging in canopy from multiple blighted twigs. Photo courtesy of Ben Faber.
Control and management of the disease depends on cultural practices, chemical control, and integrated disease control management (Michailides & Morgan, 2004). Cultural disease control practices include; pruning, and timing of pruning, avoid pruning or mechanical damage during the rainy season. Prune cankered limbs two to five inches below diseased wood. Remove pruned away dead wood from the field prior to rainy/moist periods. Disinfect pruning tools with quarter strength household bleach – can be corrosive, 100% Lysol, or surface sterilize by flame. Use drip irrigation when possible and avoid wetting the trunk and canopy of trees. When necessary, irrigate with lower pressure to avoid misting and fogging that adds to humidity. Remove weeds to reduce the humidity and habitats for other insect pests. Insects, birds, and irrigation water can aid in disseminating the disease.
Be vigilant in scouting and remove the first sources of inoculation in summertime and repeat until disease is difficult to find. Remove and burn brush from the orchard as the disease can remain viable for as long as three to six years (Michailides & Teviotdale, 2014; Michailides & Morgan, 2004) in woody debris. When possible, protect tress from stressors (water, heat, mechanical injury, salinity, frost, nutrition deficiencies, or sunburn). Soil borne pathogens can predispose plants to Botryosphaeria gummosis by disrupting water and nutrient flow. Insect pests (such as scale) can also increase disease incidents as much as 50% or higher.
Integrated pest management is crucial to mitigating this disease. Buy clean nursery stock. Keep active monitoring regimes. Surface disinfect tools and equipment between cuts. Control other diseases (such as soilborn pathogens) and insect pests. Whitewash when necessary. Most importantly, follow proper irrigation and fertilizer regimens to ensure plant health.
and there's more:
http://ceventura.ucanr.edu/newsletters/Topics_in_Subtropics80946.pdf
References
Adesemoye, A. O., Eskalen, A., Faber, B., & O'Connell, N. (2011). Multiple Botryosphaeria species causing “Dothiorella” gummosis in citrus. Citrograph, 2(2), 32-34.
Faber, B. Citrus ID and Control. University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program.
Michailides, T.J., Morgan, D. P., (2004). Panicle and Shoot Blight of Pistachio: A Major Threat to the California Pistachio Industry. American Phytopathological Society. http://www.apsnet.org/publications/apsnetfeatures/Pages/Pistachio.aspx
Michailides, T.J., Teviotdale, B.L., (2014). Pistachio: Botryosphaeria Panicle and Shoot Blight. University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program. http://ipm.ucanr.edu/PMG/r605100311.html
- Author: Ben Faber
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- Author: Ben Faber
Lemon Scions and Lemon Rootstocks Workshop & Field Tour
October 17, 2019
8:00am-12:00 PM
Visitors Center, Limoneira Co., 1141 Cummings Rd, Santa Paula, CA 93060 View map/directions here
Contact: Ben Faber, 805-645-1462, bafaber@ucanr.edu
Which Way Lemon Industry?
What are Lemon Rootstock Choices?
What are Lemon Scion Choices?
How are they Complementary?
What are their Effects on Yield? Fruit Quality? Canopy Growth? Soil Compatibility? Tree Health?
HLB Tolerance? Maybe We Know a Little.
How do Scions and Rootstocks Compare in the Desert, Valley and Coast?
Come Learn this and more. Tour a Scion/Rootstock Trial
Speakers:
Mike Roose, UC Riverside Citrus Breeder
Tracy Kahn, UC Riverside Curator Citrus Collection
Glenn Wright, University of Arizona Citrus Extension Specialist
Ashraf El-Kereamy, UC Riverside Citrus Specialist
