- Author: Ben Faber
A recent blog by Farm Advisor Rachel Freeman Long in Yolo/Solano/Sacramento Counties alerted me to a weed that I thought was mainly a northern California plant.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26918
But according to Calflora it's been found in Agoura Hills and Moorpark with two sightings in San Luis Obispo County.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=7048
Spiny buttercup (Ranunculus muricatus) is a non-native plant, that is fairly common, especially in wet areas such as meadows. We also find it in crops, including orchards, pastures, and cereal grain fields. It's both an annual and perennial plant that blooms from March to May, with seed pods that are large and prickly. Though it's pretty with the bright yellow flowers, don't be fooled, as it has a dark side, so should be controlled.
First, according to Dr. Birgit Puschner, UC Davis Vet Med Toxicologist, all buttercups contain ranunculin, though there are differences in species in terms of toxin levels. In pastures, because the plant is bitter, animals simply eat around it. But if ingesting the fresh plant, they can develop blisters. The toxin degrades in hay; thus, it's only a problem in grazing and fresh exposures.
Second, according to Dr. Gilbertson, UC Davis Plant Pathologist and Ozgur Batuman, former UCD Post Doc, buttercup is a significant host of tomato spotted wilt virus (TSWV). Other important weed hosts for TSWV include cheeseweed (Malva parviflora), sowthistle (Sonchus oleraceus), and prickly lettuce (Lactuca serriola). TSWV crop hosts include peppers, tomato, lettuce, and bell beans (fava).
The primary vector of TSWV is the western flower thrips, a tiny insect that feeds on the plant foliage. Immature thrips pick up this pathogen from infected plants and transmit it to healthy ones when they become adults and disperse to new host plants. TSWV is not transmitted via seed.
Symptoms of TSWV typically include necrotic spots, often with tip or leaf dieback that looks like drift from a contact broadleaf herbicide. However, there is a lot of variability in the symptoms of TSWV depending on the host that could be confused with other problems. As such, if you suspect TSWV in your crop, the best way to positively identify it is by using on-site tools to test for this disease, such as ImmunoStrip® tests. A good resource for TSWV in tomatoes is: Tomato spotted wilt disease in tomatoes.
Watch for spiny buttercup and control this weed to keep it from spreading. We need to keep our pastures safe and TSWV out of our crops.
/span>- Author: Ben Faber
Los Angeles County Spring 2018 ISHB/GSOB Field Trainings
Registration now open
Learn how to recognize the signs of invasive shot hole borer and gold spotted oak borer infestations in native and landscape trees. Each training will cover how to recognize signs, symptoms, active and inactive populations, take field samples, treatment options, proper handling and disposal of green waste.
- Huntington Gardens, Tuesday May 8, 10:30 - 12:30
training entrance: 1800 Orlando Avenue, San Marino CA 91108
2) O'Melveny Park, Thursday May 17, 10:00 - 12:00
17300 Sesnon Blvd, Granada Hills CA 91344
The events are free, but registration is limited. To register, go to www.pshb.org and click on the calendar entry, or go directly to http://ucanr.edu/sites/gsobinfo/News_and_Events/GSOB_Training_Event_Registration/?editon=0
These trainings were initially offered as part of a series with two live webinars, which have now past – if you did not attend the webinars, unfortunately, these trainings alone will NOT offer CEUs.
AS OF 5/3/2018, THE ONLY FIELD TRAINING WITH SPACE REMAINING IS THURSDAY, MAY 17TH, O'MELVENY PARK, LOS ANGELES COUNTY. IF YOU CANNOT ATTEND THIS TRAINING, DO NOT REGISTER.
- Author: Ben Faber
RIVERSIDE, Calif. (http://www.
HLB, also known as citrus greening disease, has devastated groves in Asia, South America, and the southern U.S., costing the Florida citrus industry billions of dollars since 2005. Since 2012, the disease has been spreading in California's residential areas, prompting serious concerns about the state's commercial citrus groves.
HLB is associated with a species of bacteria called Candidatus Liberibacter asiaticus (CLas), which is transmitted by a tiny insect called the Asian citrus psyllid (ACP). Infected trees show leaf mottling, deformed and discolored fruits, and premature fruit drop. There is no cure for the disease and once a tree is infected it typically dies within three to five years.
An important step to developing HLB-resistant citrus varieties is to better understand how the bacterium infects trees and causes disease.
"Citrus trees, like all plants, have complex immune systems to prevent pathogenic infection, so the question is 'how does the CLas pathogen evade that immunity so it can cause disease?' said Wenbo Ma, a professor of plant pathology in UCR's College of Natural & Agricultural Sciences.
In a paper published Monday in Nature Communications, a team led by Ma reported a significant breakthrough in understanding the disease mechanism of HLB. They discovered that the bacterium secretes a protein--called Sec-delivered effector 1 (SDE1)--that helps infect plants. SDE1 works by attacking specific proteases--called papain-like cysteine proteases (PLCPs)--that could otherwise help the citrus trees resist infection.
"In the diseased trees we studied, the protein levels of some PLCPs were increased, presumably attempting to combat the bacterial infection," Ma said. "However, the bacterium fights back, by inhibiting the enzymatic activity of PLCPs through SDE1."
Ma said since scientists cannot grow CLas in the laboratory, the team used a surrogate system comprising the model plant Arabidopsis thaliana and the bacterial pathogen Pseudomonas syringae that was genetically engineered to produce SDE1. Using this system, they show that SDE1 promotes bacterial infection. This study is among the first to describe the molecular tactics employed by CLas to colonize citrus plants.
"This study represents an important step towards better understanding the HLB disease mechanism, which will help us develop novel approaches to control this unstoppable disease," Ma said.
The team is now investigating the molecular details of how SDE1 suppresses citrus PLCPs with the aim to use the CRISPR gene editing system to modify the proteases to become resistant to the inhibitory effects of SDE1.
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The title of the paper is 'An effector from the Huanglongbing-associated pathogen targets citrus proteases.' In addition to Ma, authors from UC Riverside are Kelley Clark, Simon Schwizer, Eva Hawara, Deborah Pagliaccia, Liping Zeng, Jinxia Shi, Pengcheng Wang and Yinsheng Wang. Other authors include Jessica Yvette Franco, Thomas Liebrand and Gitta Coaker from UC Davis; Zhiqian Pang and Nian Wang from the University of Florida; Fatta B. Gurung and Veronica Ancona from Texas A&M University; and Renier van der Hoorn from the University of Oxford.
Funding was from the United States Department of Agriculture (USDA) National Institute of Food and Agriculture.
IMAGE: An orange tree that is infected with huanglongbing. Leaf symptoms begin on one or a few branches and slowly spread to the rest of the tree. view more
Credit: Georgios Vidalakis, UC Riverside
- Author: Ben Faber
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- Author: Ben Faber
Ambrosia beetles comprise a group of over 6,000 species in the Scolytinae subfamily. Most of these beetles typically attack decomposing and dead trees. The Polyphagous/Kuroshio Shot Borers have been reports on over 300 landscape and wildland living tree species, including avocado. Decline and death of trees has been noted in California since 2012, and the full economic extent is still unclear. The beetles feeds on a fungal symbiont that is introduced into the tree, and it is the fungus that spreads throughout the tree and causes the tree decline and death.
What was once thought to be another species of beetle (Tea Shot Hole Borer) and then identified as a new species - Polyphagous Shot Hole Borer- and now expanded to include another species of borer – Kuroshio Shot Hole – is showing that its fungal partners can be quite diverse. A recent publication indicates the increasing tangled association of the shot hole borer/disease complex that is affecting avocado and other tree species.
Two Novel Fungal Symbionts Fusarium kuroshium sp. nov. and Graphium kuroshium sp. nov. of Kuroshio Shot Hole Borer (Euwallacea sp. nr. fornicatus) Cause Fusarium Dieback on Woody Host Species in California
Francis Na, Joseph D. Carrillo, Joey S. Mayorquin, Cedric Ndinga-Muniania, and Jason E. Stajich, Department of Plant Pathology and Microbiology, University of California, Riverside, 92521; Richard Stouthamer, Department of Entomology, University of California, Riverside, 92521; Yin-Tse Huang, Department of Plant Pathology, National Chung Hsing University, Taichung 402, Taiwan, ROC, and School of Forest Resources and Conservation, Institute of Food and Agricultural Sciences, University of Florida, Gainesville; Yu-Ting Lin and Chi-Yu Chen, Department of Plant Pathology, National Chung Hsing University, Taichung 402, Taiwan, ROC; and Akif Eskalen,† Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
https://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-07-17-1042-RE
Shot hole borer (SHB)-Fusarium dieback (FD) is a new pest-disease complex affecting numerous tree species in California and is vectored by two distinct, but related ambrosia beetles (Euwallacea sp. nr. fornicatus) called polyphagous shot hole borer (PSHB) and Kuroshio shot hole borer (KSHB). These pest-disease complexes cause branch dieback and tree mortality on numerous wildland and landscape tree species, as well as agricultural tree species, primarily avocado. The recent discovery of KSHB in California initiated an investigation of fungal symbionts associated with the KSHB vector. Ten isolates of Fusarium sp. and Graphium sp., respectively, were recovered from the mycangia of adult KSHB females captured in three different locations within San Diego County and compared with the known symbiotic fungi of PSHB. Multigene phylogenetic analyses of the internal transcribed spacer region (ITS), translation elongation factor-1 alpha (TEF1-α), and RNA polymerase II subunit (RPB1, RPB2) regions as well as morphological comparisons revealed that two novel fungal associates Fusarium kuroshium sp. nov. and Graphium kuroshium sp. nov. obtained from KSHB were related to, but distinct from the fungal symbionts F. euwallaceae and G. euwallaceae associated with PSHB in California. Pathogenicity tests on healthy, young avocado plants revealed F. kuroshium and G. kuroshium to be pathogenic. Lesion lengths from inoculation of F. kuroshium were found to be significantly shorter compared with those caused by F. euwallaceae, while no difference in symptom severity was detected between Graphium spp. associated with KSHB and PSHB. These findings highlight the pest disease complexes of KSHB-FD and PSHB-FD as distinct, but collective threats adversely impacting woody hosts throughout California.