Archive for the ‘Plant Pathogens’ Category


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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BY KSRE | April 13, 2017

Kansas State University, Australian Researchers Join Forces to Combat Insect Pest

Photo courtesy of KSRE

MANHATTAN, Kan. – Researchers at Kansas State University and the University of Queensland in Australia have joined forces to attack and control a microscopic pest that can be devastating to the fruit, vegetable and flower industries.

Ralf Dietzgen, an associate professor in agriculture and food innovation at the University of Queensland, is spending three months at K-State as a Fulbright Senior Scholar in a quest to gather data and develop control measures for the small insect known as thrips.

Dietzgen is working directly with plant pathology professors Dorith Rotenberg and Anna Whitfield, who are co-directors of the Center of Excellence for Vector-Borne Plant Virus Disease Control.

Not known to grow larger than 3 millimeters, thrips are voracious eaters, using their asymmetrical mouths to puncture the surface of food crops, flowers and leaves and suck up their contents.

Of equal concern to researchers is that thrips are vectors, or carriers, of more than 20 viruses that cause plant disease, especially the tospoviruses, which also multiply in thrips. Given the right conditions, such as those found in greenhouses, thrips can reproduce exponentially and form large swarms that can transmit viruses to healthy plants.

“They’re very challenging to control, for several reasons,” Whitfield said. “For one, the insect is hard to kill. It is resistant to many insecticides. You can’t just spray crops and hope to control the spread of thrips and tospovirus.

“But secondly, the viruses that thrips can spread are very diverse and can change quickly. I call tospoviruses the influenza of the plant virus world. The predominant virus threat may change because they can switch genome segments and can develop resistance to control measures based on genetic changes. So the viruses have a lot of diversity themselves.”

Whitfield said Dietzgen’s lab in Australia is one of a few in the world that studies viruses that replicate in insects and plants.

“The thrips are a significant pest and have an impact on food security and then on top of that they transmit viruses which cause disease symptoms on the produce, like ring spots, which make them unmarketable,” Dietzgen said.

He noted that when thrips feed on flower buds, the developing fruits often become misshapen. “So you have peppers that are crooked and unmarketable,” Dietzgen said.

“We are studying thrips and the viruses they transmit at the molecular level with the goal of developing applied control strategies,” Whitfield said. “We think that better understanding the molecular mechanisms of the interaction is essential for developing sustainable control strategies for thrips and tospoviruses.”

Dietzgen recently saw first-hand the devastation that thrips-transmitted viruses can cause. One Queensland grower who provides fresh tomatoes for a large supermarket chain lost most of his crop one year due to a tospovirus transmitted by thrips. The lost crop was valued at more than $500,000.

“By the time the grower saw the disease effects, the thrips had moved on and the virus had been left behind,” Dietzgen said.

“The virus that Ralf is studying isn’t in the U.S. just yet, but thrips insects are able to move around easily so that they could appear hidden in a shipment of produce,” Whitfield said. “Any shipment of vegetables or plants that is traveling around the world could have similar pathogens and pests in it. As a control measure, we are trying to develop broad spectrum, durable resistance using different technologies.”

While Dietzgen’s stay at Kansas State University is relatively short, the researchers hope their new partnership will help lead to long-term solutions for agriculture.

“Both of our labs have generated large sets of genomic data that we’re starting to compare during my stay,” Dietzgen said. “By doing that, we hope to come up with potential targets for pest and disease control for longer term crop protection. We are asking, ‘What are the functions of these potential molecular targets and can we interfere with them?’”

Rotenberg and graduate student Derek Schneweis have compiled large sets of data outlining the messenger RNA molecules in thrips. Whitfield said their work may give new insight into how to control thrips in horticultural crops, as well as how to protect those crops from tospoviruses and other plant disease.

The prestigious U.S. Fulbright program is the largest educational scholarship of its kind, and was created after World War II by U.S. Sen. J. William Fulbright. It operates between the U.S. and 155 countries.

More than 20 Fulbright Scholarships are awarded each year to Australian students, postdoctoral researchers, academics and professionals to pursue studies or conduct research in the United States.

In 2014, Kansas State University became the first U.S. educational partner of the Australian-American Fulbright Commission. Each year since, the university has hosted Fulbright Scholars from Australia to study and collaborate with Kansas State University researchers.

Kansas State also helped form the Oz to Oz program to encourage exchanges with faculty at Australian universities, often as seminar speakers.

© 2017 Nebraska Rural Radio Association. All rights reserved. Republishing, rebroadcasting, rewriting, redistributing prohibited. Copyright Information

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Deciphering plant immunity against parasites

April 13, 2017

Deciphering plant immunity against parasites
These researchers are from the Department of Molecular Phytomedicine at the University of Bonn. Credit: Molekulare Phytomedizin/Uni Bonn

Nematodes are a huge threat to agriculture since they parasitize important crops such as wheat, soybean, and banana; but plants can defend themselves. Researchers at Bonn University, together with collaborators from the Sainsbury Laboratory in Norwich, identified a protein that allows plants to recognize a chemical signal from the worm and initiate immune responses against the invaders. This discovery will help to develop crop plants that feature enhanced protection against this type of parasites. The work is published in the current issue of PLoS Pathogens.


Plant-parasitic nematodes are microscopic worms that parasitize their to withdraw water and nutrients. The feeding process seriously damages the host plant. Nematode infection distorts root and shoot structure, compromises the plant´s ability to absorb nutrients from soil, and eventually reduces crop yield. Yearly losses exceed ten percent in important such as wheat, soybean, and banana. In addition to causing direct damage, nematode infection also provides an opportunity for other pathogens to invade and attack the host plants.

Until now, near to nothing was known about the general innate of plants against nematodes. A team of researchers at the University of Bonn, in cooperation with scientists from the Sainsbury Laboratory in Norwich, has now identified a gene in thale cress (Arabidopsis thaliana), called NILR1, that helps plants sense nematodes. “The NILR1 is the genetic code for a receptor protein that is localized to the surface of plant cells and is able to bind and recognize other molecules,” says Prof. Florian Grundler, chair at the Department of Molecular Phytomedicine at the University of Bonn. “NILR1 most probably recognizes a molecule from nematodes, upon which, it becomes activated and immune responses of plants are unleashed.”

NILR1 recognizes a broad spectrum of nematodes

Although a few receptors, so-called resistance genes, providing protection against specific types of plant-parasitic nematodes have already been identified, NILR1 recognizes rather a broader spectrum of nematodes. “The nice thing about NILR1 is that it seems to be conserved among various and that it provides protection against many nematode species,” says group leader Dr. Shahid Siddique. “The discovery of NILR1 also raises questions about the nematode derived molecule, whose recognition is thought to be integral to this process.” Now that an important receptor is discovered, the scientists are working to find the molecule which binds to NILR1 to switch on the immune responses. The two first authors, PhD students at the department share tasks in the project. Whereas Mary Wang´ombe focuses on the receptor protein and its function, Badou Mendy concentrates on isolating the signal molecule released by the nematodes.

New options for breeding resistant crop plants

The findings of the University Bonn Scientists open new perspectives in making crops more resistant against nematodes. They could already show that important crop plants such as tomato and sugar beet also possess a functional homologue of NILR1 – an excellent basis for further specific breeding. Once the nematode signal is characterized, a new generation of natural compounds will be available that is able to induce defense responses in thus paving the way for safe and sustainable control.

Explore further: Researchers discover a new link to fight billion-dollar threat to soybean production

More information: Mendy, B., Wang’ombe, M.W., Radakovic, Z., Holbein, J., Ilyas, M., Chopra, D., Holton, N., Zipfel, C., Grundler, F.M.W., and Siddique, S.: Arabidopsis leucine-rich repeat receptor-like kinase NILR1 is required for induction of innate immunity to parasitic nematodes, PLoS Pathogens, Internet: doi.org/10.1371/journal.ppat.1006284

Read more at: https://phys.org/news/2017-04-deciphering-immunity-parasites.html#jCp

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AUT Student Journalism

Team effort to fight threatening fungal plant disease


Ashleigh Martin April 8, 2017

<!– Ashleigh Martin –>

Team effort to fight threatening fungal plant disease

Look out for yellow powdery eruptions on leaves. Photo: Supplied / M Daughtrey, Cornell University

The Ministry of Primary Industries has issued a call to arms after a fungal plant disease which could affect New Zealand native plants and our honey industry was found on Raoul Island.

The disease, myrtle rust, can be identified by bright yellow powdery eruptions on leaves and attacks various species of plant such as pōhutukawa, kānuka, mānuka and non-natives like the feijoa plant.

Amid fears the disease could spread to these shores, MPI is working with DOC and the New Zealand Defence Force to survey Raoul for it.

David Yard, MPI incident controller, said several DOC workers were going over the island, so a joint plan could be made.

“They’ve been briefed on how to minimise the risk of spreading it…because obviously the risk is if you work through an affected area, you might actually spread the disease,” Mr Yard said.

Raoul Island is 1100km away from the nearest part of the New Zealand mainland. The island is also very rocky and mountainous, making work difficult.

“We’ve been working with the Defence Force should we need to get materials, equipment and people onto the island to support DOC efforts,” Mr Yard said.

The disease can travel long distances by wind and can also be transported by insects, rain splashes and contaminated clothing.

The Wellington-based Science Media Centre quoted Dr David Teulon, director of Better Border Biosecurity, who said myrtle rust had been spreading rapidly around the world in recent years.

“If it reached mainland New Zealand, it could have a serious impact on a number of our taonga Māori plant species, such as pōhutukawa and rātā, with severe infections causing plants to die,” Dr Teulon said.

“Plants that are also important to our honey industry, such as mānuka and kānuka, could also be affected, which could severely impact on New Zealand’s annual $300 million of honey exports.”

– See more at: http://www.tewahanui.nz/environment/team-effort-to-fight-threatening-fungal-plant-disease#sthash.vF0oxCzv.dpuf

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Development of strategy to reduce Cambodian farmers’ reliance on pesticides is on track

 Rica Joy Flor   |  

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Mr. Chou Cheythyrith, EPIC project partner from GDA, (facing camera) explains the experiment on Trichoderma and pest-resistant rice varieties to visiting farmers and representatives from various NGOs, and public and private institutes. (Photos: EPIC project)

PREY VENG, Cambodia—An important strategy to reduce reliance on chemical pesticides in Cambodia is steadily moving through a project that encourages the use of environment-friendly biological control agents (BCA).

Over the last decade, Cambodian rice farmers have mainly relied on chemical pesticides as a major method for controlling pests and diseases. Experts warn that the rampant use of toxic chemicals is likely to lead to numerous long-term effects on the health of farmers and the environment. Integrated pest management (IPM) and BCA provide an alternative to chemical pesticides. BCAs include insects, fungi, and other natural products to manage pests.

The project, EPIC (Development of ecologically-based, participatory IPM package for rice in Cambodia), is helping pave the way for the greater use of BCAs by providing policymakers with science-based information on the effectiveness of BCAs and their benefits on the environment and human health.

Participants from government institutions discuss the effectiveness of BCAs during the site visit.

On 17 March, officers from Cambodia’s Department of Agricultural Legislation, various departments from the General Directorate of Agriculture, and private companies visited the EPIC trial site on Trichoderma (a common soil fungus), pest-resistant rice varieties, and weed management in Prey Veng. The participants were able to observe the practice of IPM using a bio-control agent on commonly used and pest-resistant rice varieties. They also discussed with the researchers the effectiveness and possible effects of Trichoderma on the environment and human health, the responses of the farmers who observed the experiments, and the possible steps for their respective organizations in promoting the technology.

Following the visit, a consultative meeting was held on 27 March with officials from various departments under the Ministry of Agriculture, Forestry and Fisheries, research institutes, and private-sector groups to discuss the registration form for BCAs. All these aim to facilitate the endorsement from the Ministry that will lead to the production of effective, safe and good-quality BCA products in Cambodia that can be made readily available to farmers.

EPIC is a 4-year project led by the International Rice Research Institute and funded by United States Agency for International Development under the Feed the Future Innovation Lab for Integrated Pest Management. The site visit was implemented in collaboration with Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH (GIZ).

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From PestNet

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Wed 22 Mar 2017
Source: MBC Malawi [edited]

Malawians have been warned to look out for maize lethal necrosis [MLN]
disease that has been attacking maize in other neighboring countries.

Johnny Masangwa, Department of Agricultural Research, said, “We are
conducting MLN survey in every district and found that the disease was
not yet in. We are carrying awareness messages as a preventative
measure to contain its spread this year [2017].” In case of an
incursion of MLN, there will be a quarantine of that area and lessons
to farmers on how to limit its spread.

[Byline: Litness Chaima]

Communicated by:

[Maize lethal necrosis (MLN) is caused by co-infection of _Maize
chlorotic mottle virus_ (MCMV, genus _Machlomovirus_, transmitted by
chrysomelid beetles) with one of several species in the family
_Potyviridae_. As synergistic partners of MCMV in MLN, _Wheat streak
mosaic virus_ (WSMV, genus _Tritimovirus_) or _Maize dwarf mosaic
virus_ (MDMV, genus _Potyvirus_) have been reported previously from
the Americas and Europe. MLN as well as MCMV were reported for the 1st
time in Africa from Kenya in 2012 (ProMED-mail post
http://promedmail.org/post/20130123.1510727). The disease is spreading
in the region where millets have also been identified as an additional
crop host being affected by MLN (ProMED-mail post
http://promedmail.org/post/20150820.3590521). _Sugarcane mosaic virus_
(SCMV) has been reported as the co-infecting virus in Sub-Saharan
Africa, but MDMV and SCMV belong to a complex of closely related
potyviruses infecting tropical grasses. Based on serology, some
strains (for example, MDMV-B) varying in host range and ability to be
seed transmitted have been reassigned between the species which has
resulted in some confusion in taxonomy.

Symptoms of the individual viruses are synergistically enhanced in MLN
and may include leaf mottling and necrosis, distortion of ears,
absence of kernels, failure to produce tassels, as well as stunting,
premature aging, and death of plants. Symptoms may disappear during
the growing season leaving plants with latent infections but reduced
yield and as virus reservoirs, making disease monitoring difficult.
While MCMV is not seed transmitted, the synergistic partner viruses
WSMV and MDMV (including some reassigned strains previously included
in SCMV) are. Thus, losses from MLN are both due to yield reductions
and trade implications resulting from the risk of virus infected seed.
Infectious vector insects may be carried by wind over long distances.
Disease management may include crop rotation, certified clean seeds,
control of vector species and weedy reservoir hosts, as well as use of
crop cultivars or hybrids with reduced sensitivity to the viruses.

The perceived high risk of a MLN incursion in Malawi, as reported
above, is entirely justified since the disease has been reported from
immediate neighbours Mozambique (ProMED-mail post
http://promedmail.org/post/20131004.1983210) and Tanzania (ProMED-mail
post http://promedmail.org/post/20130403.1620327). While it is being
reported that surveys have not detected the disease in the country as
yet, it is not stated which survey methods were used. If surveys were
only conducted from symptoms and/or without molecular diagnosis on
samples, MLN may well be present already in Malawi but has remained

Africa, overview:

Maize lethal necrosis:
Symptoms of MCMV, SCMV and MDMV single infections in maize via:

Information on maize lethal necrosis:
Information on MCMV:
<http://www.dpvweb.net/dpv/showdpv.php?dpvno=284> and
Information on MDMV:
Information on SCMV:
Virus taxonomy via:
– Mod.DHA]

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A number of citrus trees in Malta have been infected with a deadly virus, a surveillance programme has found. The infected trees, originating from Sicily, were discovered in various garden centres following sampling and testing. The monitoring was carried out by the Plant Health Directorate within the Parliamentary Secretariat for Agriculture with the objective of monitoring the status of pest occurrence.The directorate activated the contingency plan and carried out the destruction of the infected consignments. To ensure the eradication of this pest, the public is being asked to notify the directorate of any purchase of citrus trees in the last six months.

The Citrus Tristeza Virus is the most destructive citrus disease worldwide. The most recent outbreak dates back to 2012 when an area in San Blas and Daħlet Qorrot Valleys in Gozo was demarcated.

The virus cannot be controlled by pesticides, and the only control mechanism for this disease is that of uprooting and burning infected trees and applying pesticides for the vectors.

For more information:
The Plant Health Directorate
Tel: +356 2292 6535

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