Archive for the ‘Bacteria’ Category

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2017/065 First reports of a new bacterial leaf blight of rice caused by Pantoea anana and Pantoea stewartii in Benin and Togo

In Benin, surveys were carried out from 2011 to 2015 in rice fields to assess the importance of bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (EPPO A1 List). Symptomatic leaf samples were collected and tested. As all isolates gave negative results in a multiplex PCR test for X. oryzae, further studies were conducted and revealed the presence of bacteria belonging to the genus Pantoea. Molecular and pathogenicity tests (to fulfill Koch’s postulates) confirmed that the bacteria which had been isolated from rice leaves were P. ananatis and P. stewartii (EPPO A2 List). It is noted that symptoms were  observed in all surveyed localities (14 sites) with a disease incidence varying from 30 to 100%. In Togo, surveys were also carried out in 2013 and 2014 in the main rice-growing regions (Kovié and Kpalimé) to evaluate the prevalence of plant-pathogenic bacteria. Rice leaves showing characteristic symptoms of bacterial leaf blight were collected and tested. Similarly, the bacteria which were isolated from rice leaves and grains were shown to be P. ananatis and P. stewartii. According to the authors, this is the first time that P. ananatis and P. stewartii species are found causing a leaf blight disease on rice crops in Benin and Togo. According to the EPPO Secretariat this is also the first time that P. stewartii is reported from Africa.

Source: Kini K, Agnimonhan R, Afolabi O, Milan B, Soglonou B, Gbogbo V, Koebnik R, Silué D (2017) First report of a new bacterial leaf blight of rice caused by Pantoea ananatis and Pantoea stewartii in Benin. Plant Disease 101(1), p 242. Kini K, Agnimonhan R, Afolabi O, Soglonou B, Silué D, Koebnik R (2017) First report of a new bacterial leaf blight of rice caused by Pantoea ananatis and Pantoea stewartii in Togo. Plant Disease 101(1), 241-242.

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Kiwi bacteriosis control now a reality

The international Journal of Plant Disease and Protection finally published the research financed by MIPAAF and coordinated by Prof. Giorgio M. Balestra which saw the cooperation between the Department of Agricultural Sciences (DAFNE) of Università della Tuscia and the Department of Life Sciences and Biotechnology (SVeB) of the University of Ferrara

Title: “Microparticles containing gallic and ellagic acids for the biological control of bacterial diseases of kiwifruit plants

Authors: Antonio Rossetti, Angelo Mazzaglia, Massimo Muganu, Marco Paolocci, Maddalena Sguizzato, Elisabetta Esposito, Rita Cortesi, Giorgio Mariano Balestra.

It is a lengthy study that demonstrates how it is possible to use vegetable substances to monitor the different phytopathogenic bacteria that cause much worry in all the areas growing Actinidia spp..

The cultivation of actinidia to produce kiwis has become increasingly important in Italy as well as in various areas around the world. At the same time, however, bacterial diseases are affecting its cultivation. The most dangerous is without doubt the bacterial canker caused by Pseudomonas syringae pv. actinidiae (Pss) Takikawa et al., also known as Psa, which damages all vegetative organs.

Serious damage is caused also by the drop in temperatures in spring, as is the case this year, associated with other two bacteria – Pseudomonas syringae pv. syringae (Pv) van Hall, responsible for floral bud necrosis and Pseudomonas viridiflava (Burkholder) Dowson, the bacterial blight which affects leaves and floral organs.

In Italy, prevention is carried out by using copper salts as well as a biological control agent (B. a. subsp. plantarum ceppo D747) during blossoming. Other areas outside the EU employ antibiotics with serious repercussions on the environment and leading to the development of antibiotic-resistant bacteria strains.

This study assessed the effectiveness of gallic and ellagic acids, i.e. natural substances that are easily attainable from many vegetable tissues and with high anti-microbial properties.

These natural, active principles proved effective as pure substances both in the lab and in vivo (greenhouses, then open-field actinidia orchards naturally affected by Pss, Pv and Psa).The vegetable active principles significantly reduced the various bacterial populations as well as the damage caused both through artificial contamination and by using them on orchards naturally affected by Pss, Pv and Psa.

In association with the intrinsic activities, the active principles proved particularly effective when employed through micro-formulations in micro-capsules, thus preventing alterations (physical-chemical) and enabling a controlled release of the principles over two weeks protecting all vegetable organs.

In addition, the activity of these formulations on both plant development and final production was also assessed. All parameters showed how these micro-formulations do not affect plant development (the plants treated with micro-capsules had a higher chlorophyll content in the leaves and the fruits, though with the same size and Brix level, were more compact).

The results obtained with this study represent a significant contribution towards the attainment of formulations that can successfully counter dangerous micro-organisms like those affecting actinidia with a sustainable/organic approach.

Reducing the use of copper salts to protect crops is a process dictated by the EU. As of January 2018, further reductions of Cu++ will be introduced, thus valid alternatives must be found.

This study suggests how gallic and ellagic acids, when formulated together in microformulations, can be successfully employed in sustainable/organic defence strategies against pathologies like those currently affecting actinidia.

The active principles and technology used in this research constitute an important base, as what described can be applied to different pathogens/ crops, thus reducing the use of chemicals and therefore chemical residue.

Additional studies are currently being carried out concerning organic nano-formulations for the protection of different crops both in the fields and during the storage and commercialisation stages. They aim at a further reduction of the (natural) active principles used, at a prolonged controlled release and at making it so that formulations can penetrate fruit/plants and target the pathogen.

For further information:
Prof. Giorgio M. Balestra
DAFNE (Department for Agriculture, Forestry, Nature and Energy)
University of Tuscia
Via S. Camillo de Lellis
01100 Viterbo
Tel.: (+39) 0761 357474
Cell.: (+39) 333 4246404
Fax: (+39) 0761 357473
Email: balestra@unitus.it
Web: www.unitus.it
Skype: giorba5618
Personal page: www.dafne.unitus.it/web/interna.asp?idPag=1118

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Black Rot Disease Affecting Cabbage Growing Season

Posted: May 04, 2017 6:33 PM CDT Thursday, May 4, 2017 7:33 PM EDTUpdated: May 04, 2017 6:33 PM CDT Thursday, May 4, 2017 7:33 PM EDT

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NEAR EDINBURG – Many Rio Grande Valley farmers are trying to recoup their losses after the black rot disease invaded their cabbage crops.

Edinburg farmer Tommy Hanka’s company, Tommy Hanka Farms, grows cabbage as well as other cool season vegetables in a 1,000-acre farm land.

Hanka said the recent record heat was terrible news for farmers.

“Well, it affected me on my green cabbage and red cabbage. I had some black rot issues. I ended plowing under over 75 percent… It was just not marketable. It was a real disaster, a real train wreck this year,” he said.

Hanka said farmers and the local economy are affected when there is a bad growing season.

“The box companies don’t get paid, the trucking companies don’t get paid because there is no product to move. There’s no produce to sell. We just can’t employ these guys because there is no work,” he said.

Texas A&M AgriLife Extensions vegetable specialist Juan Anciso said other farmers also saw big losses this growing season.

He said about half of the 3,000 acres of cabbage planted this season was lost due to black rot.

“Warm weather – for example for bacteria – it increases their reproduction rate so you have more bacteria,” he said. “And we have had a serious problem with black rot, which is a bacterial pathogen in cabbage. It’s a disease that has been around since cabbage has been around. But we haven’t had these problems since the 1980s.”

Anciso explained black rot enters through the leaves and causes them to turn black and brown, making the cabbage unsellable.

But Hanka said although this year’s season was extremely tough he’s not giving up.

“Let’s move on. We are going to stick to the game plan. We are going to do the same thing we did this year. We are going to be here next year…. It’s only going to get better,” he said.

Anciso said Texas AgriLife will continue to look for black rot resistant strains of cabbage. He said farmers will then be better equipped to turn a profit during unusually warm season.

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Subject: Cucurbit wilt- Erwinia tracheiphila

Scientific American


  •  spotted cucu beet
  • Spotted cucumber beetle, one of two species confirmed to carry the Erwinia trachaephila  bacterium, on a zucchini leaf. Credit: Scott Chimelski

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Huanglongbing is causing concern in California – California Agriculture News | California Agriculture


April 27, 2017

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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West Australian potato disease threat stunts trade as growers warned spread ‘almost inevitable’ – ABC Rural – ABC News (Australian Broadcasting Corporation)

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West Australian potato disease stunts trade as growers warned spread ‘almost inevitable’

Posted 30 Mar 2017, 5:26pmThu 30 Mar 2017, 5:26pm

More than 5,000 tonnes of Western Australian seed potato could be dumped due to trade restrictions put in place to deal with the tomato potato psyllid (TPP) outbreak.

The Department of Agriculture and Food of WA (DAFWA) is currently assessing whether the bacterium Candidatus liberibacter solanacearum is present in the state, which has the potential to cause the damaging zebra chip disease in potatoes.

The psyllid was detected in the state last month, which was the first time it had ever been discovered in Australia.

DAFWA introduced new quarantine measures to help contain an outbreak of the psyllid last week as a national plan was released to help monitor and contain the movement of vegetables and seedlings.

The executive director of biosecurity and regulation for the department Kevin Chennell said the disease was going to prove difficult to eradicate.

“There’s national consensus that it’s going to be very difficult,” he said.

“We’re going to be trying very, very hard and working with industry and community to suppress and contain TPP [but] it may be very difficult to eradicate it.”

Western Australian Potato Seed Growers chairman and Albany-based grower Colin Ayres said the restrictions on trade for seed stock interstate was frustrating for the industry.

He said seed stock from WA would need to be exported to South Australia by May if it were to be viable.

“Although everyone’s been kept up-to-date, the wheels of any government move pretty slow,” he said.

“When there’s a timeline to where this product is of no use to anyone, growers do feel frustrated that decisions aren’t made quicker.”

Mr Ayres said growers could potentially be forced to dump 5,000 tonnes of seed stock if trade restrictions were not lifted.

New Zealand experience a warning

This is the first time TPP has been discovered in Australia but the psyllid was first detected in New Zealand more than a decade ago.

The psyllid spread from where it was initially detected on the North Island and was also detected on the South Island three years ago.

Potato industry consultant Dr Iain Kirkwood worked with New Zealand growers for the past five years in attempting to contain the psyllid and zebra chip disease, which can be found in potato crops across the country.

Dr Kirkwood works as a field officer for a seed potato company, Eurogrow Potatoes.

He said, from what he had seen of the spread of the zebra chip disease in New Zealand, he believed it was “almost inevitable” that the psyllid, and the disease if it was found, would spread.

“In terms of being able to manage the disease you have to identify that it’s there first,” he said.

“The disease is a really difficult one to deal with because it’s got so many different expressions.”

But Dr Kirkwood said Western Australian growers should not give up hope.

“Don’t panic, it’s not the end of the world [and] it can be managed,” he said.

“The North Island [of New Zealand] has had it for 10 to 12 years and they’re managing it quite effectively now.”

Dr Kirkwood said growers would need to “get into a cycle” of spraying and monitoring the disease.

He said there were more and more insecticides to manage the psyllid coming on to the market all the time.

Topics: vegetables, quarantine, perth-6000

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SE farm press

This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies.

Logan Hawkes | Mar 04, 2017

Since the introduction of Huánglóngbìng (HLB–yellow dragon disease–or better known as citrus greening disease) reared its ugly head on U.S. soil in a Florida citrus grove in 2005, the disease has been a major threat to commercial citrus production across the country.

Before arriving in North America, HLB had already carved a path of destruction across the Far East, Africa, the Indian subcontinent and the Arabian Peninsula, and was discovered in July 2004 in Brazil. In its wake it left citrus growers around the world astounded at the inevitable and long-lasting risks the disease poses to global citrus industry.

During the first couple of years after reaching Florida, the disease had destroyed a huge section of the state’s successful citrus industry, and by 2009, just five years after its introduction in the region, almost every county within Florida had confirmed HLB cases among both commercial and private citrus groves. From there the disease spread

to adjoining states, eventually reaching citrus growing areas in Texas and finally as far west as California.The fight against HLB and the tiny psyllids that carry the bacteria from tree to tree is about as old as the disease itself. Recognizing the disease had the ability to threaten the global citrus industry, researchers from around the world began working on possible solutions to combat the spread of this dangerous citrus killer.

In spite of early efforts however, the tell-tale signs of the disease kept spreading.

 The early symptoms of HLB include leaves with yellowing veins appear along with asymmetrical chlorosis referred to as “blotchy mottle.” These are the most diagnostic symptoms of the disease, especially on sweet orange. Growers, ever fearful the disease would reach their trees, have been on constant lookout for leaves that are slow to develop and often with a variety of chlorotic patterns that often resemble mineral deficiencies such as those of zinc, iron, and manganese.

Regardless of treatment efforts, once established in a grove, the end result of the disease is proving to be inevitable, the complete decay and destruction of all infected trees.

Detection of the disease is one of the first hurdles facing citrus growers in modern times. When it comes to fighting HLB, growers face a number of unique challenges. For one, HLB-infected citrus trees do not show symptoms during the first year of infection, so there is a long period of time when a grower cannot visually detect an infected tree. But that hasn’t stemmed research efforts.

The spreading pandemic of the disease served to rally the global citrus industry and the many researchers who support it. Soon new and innovative treatments were being tested. In addition to antibacterial management and control and management of the psyllids that carry the disease, tree removal became a standard procedure to help curtail the rapid spread of the bacterium.

Soon, beneficial parasitoids were introduced and widely used to help control psyllid populations. Heat treatments in nurseries and on field trees covered by plastic wrap offered some slowing of the disease process in early research efforts. Hundreds of millions of dollars were being spent worldwide searching for a cure to the disease. A zinc-based bactericidal spray seemed to offer some hope.

Before long, breeders were offering new citrus varieties that were proving resistant to the bacterium that causes HLB. Bio-engineers have been devising methods to make citrus trees less attractive to the psyllids that carry the disease. But in recent months a new idea has surfaced, and while no one is ringing the bell of victory, researchers on the project are quietly voicing new hope in the war against the disease.


According to researchers, the reproductive and feeding habits of the psyllid make it the perfect carrier of the bacterium. An infected psyllid creates a localized infection when it feeds and transmits the bacterium into a citrus tree. It does not take long for the bacterium to spread throughout the plant, but the inoculum is first concentrated in the leaves and stems where the infected psyllid feeds. Female psyllids lay eggs in the same region where they feed. If these females are infected, their nymphs, which begin feeding in the infected area of the tree when they hatch, eventually acquire the bacterium, molt to the winged adult stage and disperse taking it along with them.

So researchers at the Boyce Thompson Institute, a premier life sciences research institution located in Ithaca, New York on the Cornell University campus, have concentrated their recent efforts on the psyllid itself as a possible link to the control of the disease.

Michelle Cilia, a Research Molecular Biologist at the USDA Agricultural Research Service and Assistant Professor at the Boyce Thompson Institute (BTI), and her team of researchers have been looking at a protein that makes the bellies of citrus psyllids blue and the possible connection it may have with the natural process of spreading the devastating bacterium in the first place. Researchers say Asian citrus psyllids with blue abdomens have high levels of an oxygen-transporting protein called hemocyanin.

According to Cilia, the hemocyanin protein is commonly found in the blood of crustaceans and mollusks. When harboring the bacterium Candidatus Liberibacter asiaticus ( or CLas) the disease is spread by the Asian citrus psyllid. This bacterium force the psyllids to ramp up their production of this protein. Cilia lab scientists, along with colleagues at the University of Washington and the USDA ARS at Fort Pierce, Fla., identified important protein interactions that must occur to perpetuate the transmission of bacterium to new trees.

They examined interactions occurring between the psyllid and the bacterium, and between the psyllid and its beneficial microbial partners. They also compared protein expression levels in both nymphs and adults. Their research shows that adult psyllids appear to mount a better immune response to CLas as compared to nymphs, which may explain why psyllids must acquire CLas during the nymphal stage to efficiently transmit CLas once they become adults.

“For many decades, scientists lacked the ability to look inside insects that transmit plant pathogens and understand what is going on,” said Cilia. “This is no longer true today, thanks to the painstaking work of our collaborators in the Bruce and MacCoss labs at the University of Washington. The new molecular tools developed by our University of Washington colleagues enable us to dissect the vector-pathogen relationship piece by piece to determine which components are important for transmission.”

The group showed that hemocyanin interacts with a CLas protein involved in a vital microbial metabolic pathway called the acetyl-CoA pathway. Scientists have previously targeted this set of biochemical reactions in bacteria when developing antibiotics.

John Ramsey, a USDA ARS postdoctoral associate in the Cilia lab and first author of the study, suspects that the increase in hemocyanin, and the blue color it imparts to the abdomen, could be evidence of an immune response to CLas infection. The findings raise the possibility that this response could be harnessed to help control the bacterium’s spread.

“The study is allowing you to look at your population of insects and say something about the immune system of the insect based on its color,” said Ramsey. “There’s the possibility that this could be a useful part of grove surveillance.”

In future work, the Cilia group plans to test whether there are differences in each color morph’s ability to spread the CLas bacterium. Results from this study will help inform future strategies to control citrus greening disease. Depending on which proteins they decide to target, these new approaches could prevent the psyllid from transmitting CLas or trigger an immune response against the bacterium.

This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies, said Ramsey. Such an approach may provide a longer lasting solution because the insect isn’t under pressure to evolve to survive the treatment, which commonly occurs with pesticide usage.

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