Archive for the ‘Fungi’ Category

As Georgia’s corn crop enters the tassel stage, farmers are weighing whether to make a fungicide application. And Asian soybean rust is in the state now, the earliest the troubling disease has been detected in Georgia in more than a decade.

The Asian soybean rust was confirmed in Miller County, Ga, located in southwest Georgia May 17, and this means the disease will likely be problematic for Georgia soybean producers this year, said Bob Kemerait, University of Georgia Extension plant pathologist. Growers are advised to stay alert and scout soybean fields. Current conditions favor the spread of the disease within kudzu.

And as Georgia corn progresses, rapidly entering the tassel stage, Kemerait advises growers, at the least the more disease aggressive growers, to consider a protective fungicide application. “This is especially true if southern corn rust has been detected in the area, if northern corn leaf BLIGHT is problematic in a field (typically with a less-resistant hybrid), conditions have been favorable for disease (very wet), the corn was planted LATE or if the grower is aggressive in a disease management program and wants to make sure the crop is protected,” he said.

Kemerait’s further thoughts on corn disease management at this time for Georgia are:

  • As of May 17, we have not found SOUTHERN CORN RUST in Georgia and conditions have not been especially favorable for southern rust.
  • As of May 17, we have had one report of common corn rust from Mitchell County. Common rust typically forms pustules on both sides of the leaf and does NOT need a fungicide application.
  • As of May 17, the only report of northern corn leaf BLIGHT in Georgia is from Ty Torrance in Decatur County. Northern corn leaf blight can be an important problem that requires a fungicide treatment IF it is severe (e.g., a susceptible variety and favorable weather). The NCLB in Decatur County was confined to the bottom leaves and there were only a few lesions on about one plant out of 15. The grower is right to be aware of the problem but I do not think a fungicide is needed for NCLB in that particular field.
  • Northern corn leaf SPOT has been found in Mitchell County by Andy Shirley.  Typically we do not spray for this disease, except in severe cases. The northern corn leaf spot in this field was confined to the lower leaves and did not appear to be spreading.
  • We have not detected southern corn rust in Georgia yet. Conditions over the next few days are more favorable for disease spread, but (overall) conditions have been unfavorable. I would not argue with a grower who wants to apply a fungicide at this time (to corn) as it reaches the tasseling growth stage; HOWEVER I think the grower is better advised to DELAY a fungicide application at this point and wait at least a week or so.

Information in this article courtesy of Andrew Sawyer, UGA Extension agent in Thomas County, at Thomas County Ag.

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NATURE International weekly journal of science

Devastating wheat fungus appears in Asia for first time

Scientists race to determine origin of  Bangladesh outbreak, which they warn could spread farther afield.

27 April 2016 Updated:

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Ruth Fremson/NYT/eyevine

Wheat in northern India could be threatened by an outbreak of fungal disease in Bangladesh.

Update: On 26 April, a team led by microbial population geneticist Daniel Croll, who is at the Swiss Federal Institute of Technology in Zurich, reported on github.com that the Bangladeshi wheat-blast strain is closely related to those collected in Brazilian wheat fields and on nearby weeds. His team’s analysis, which uses the data on the website Open Wheat Blast, reveals that the sample is not closely related to known rice-blast-causing strains of M. oryzae. Croll’s team concludes that wheat blast was probably introduced to Bangladesh from Brazil, and warns that other Asian countries that import Brazilian wheat, including Thailand, the Philippines and Vietnam, should be on the lookout for the disease.

Fields are ablaze in Bangladesh, as farmers struggle to contain Asia’s first outbreak of a fungal disease that periodically devastates crops in South America. Plant pathologists warn that wheat blast could spread to other parts of south and southeast Asia, and are hurrying to trace its origins.

“It’s important to know what the strain is,” says Sophien Kamoun, a biologist at the Sainsbury Laboratory in Norwich, UK, who has created a website, Open Wheat Blast (go.nature.com/bkczwf), to encourage researchers to share data.

Efforts are also under way to find wheat genes that confer resistance to the disease.

First detected in February and confirmed with genome sequencing by Kamoun’s lab this month, the wheat-blast outbreak has already caused the loss of more than 15,000 hectares of crops in Bangladesh. “It’s really an explosive, devastating disease,” says plant pathologist Barbara Valent of Kansas State University in Manhattan, Kansas. “It’s really critical that it be controlled in Bangladesh.”

After rice, wheat is the second most cultivated grain in Bangladesh, which has a population of 156 million people. More broadly, inhabitants of south Asia grow 135 million tonnes of wheat each year.

Wheat blast is caused by the fungus Magnaporthe oryzae. Since 1985, when scientists discovered it in Brazil’s Paraná state, the disease has raced across South America.

The fungus is better known as a pathogen of rice. But unlike in rice, where M. oryzae attacks the leaves, the fungus strikes the heads of wheat, which are difficult for fungicides to reach. A 2009 outbreak in wheat cost Brazil one-third of that year’s crop. “There are regions in South America where they don’t grow wheat because of the disease,” Valent says. Wheat blast was spotted in Kentucky in 2011, but vigorous surveillance helped to stop it spreading in the United States.

In South America, the disease tends to take hold in hot and humid spells. Such conditions are present in Bangladesh, and the disease could migrate across south and southeast Asia, say plant pathologists. In particular, it could spread over the Indo-Gangetic Plain through Bangladesh, northern India and eastern Pakistan, warn scientists at the Bangladesh Agricultural Research Institute (BARI) in Nashipur.

Bangladeshi officials are burning government-owned wheat fields to contain the fungus, and telling farmers not to sow seeds from infected plots. The BARI hopes to identify wheat varieties that are more tolerant of the fungus and agricultural practices that can keep it at bay, such as crop rotation and seed treatment.

Guillermo Isidoro Barea Vargas

Wheat blast strikes the heads of wheat, which are difficult for fungicides to reach.

It is unknown how wheat blast got to Bangladesh. One possibility is that a wheat-infecting strain was brought in from South America, says Nick Talbot, a plant pathologist at the University of Exeter, UK. Another is that an M. oryzae strain that infects south Asian grasses somehow jumped to wheat, perhaps triggered by an environmental shift: that is what happened in Kentucky, when a rye-grass strain infected wheat.

To tackle the question, this month Kamoun’s lab sequenced a fungus sample from Bangladesh. The strain seems to be related to those that infect wheat in South America, says Kamoun, but data from other wheat-infecting strains and strains that plague other grasses are needed to pinpoint the outbreak’s origins conclusively.

The Open Wheat Blast website might help. Kamoun has uploaded the Bangladeshi data, and Talbot has deposited M. oryzae sequences from wheat in Brazil. Talbot hopes that widely accessible genome data could help to combat the outbreak. Researchers could use them to screen seeds for infection or identify wild grasses that can transmit the fungus to wheat fields.

Rapid data sharing is becoming more common in health emergencies, such as the outbreak of Zika virus in the Americas. Kamoun and Talbot say that their field should follow suit. “The plant-pathology community has a responsibility to allow data to be used to combat diseases that are happening now, and not worry too much about whether they may or may not get a Nature paper out of it,” says Talbot.

Last month, Valent’s team reported the first gene variant known to confer wheat-blast resistance (C. D. Cruz et al. Crop Sci. http://doi.org/bfk7; 2016), and field trials of crops that bear the resistance gene variant have begun in South America. But plant pathologists say that finding one variant is not enough: wheat strains must be bred with multiple genes for resistance, to stop M. oryzae quickly overcoming their defences.

The work could help in the Asian crisis, says Talbot. “What I would hope for out of this sorry situation,” he says, “is that there will be a bigger international effort to identify resistance genes.”

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npr News

By Jessica Meszaros • Apr 27, 2016
orange pfd_1
You can find these “buttons” on some orange trees across Florida. They’re indicators of a fungus known as PFD, or post bloom fruit drop. An infected tree will drop fruit prematurely and leave these behind. They normally fall off with healthy oranges.

Jessica Meszaros / WGCU News

A fungal disease is affecting all types of orange trees statewide right now. It’s called PFD, or post bloom fruit drop. The fungus causes oranges to fall off prematurely. El Niño weather patterns that brought rainy, foggy days this winter helped spread the disease.

orange pfd_2

Bryan Beer is a fifth generation orange grower in Southwest Florida. At one of the groves he manages in Hendry County, Beer said he’s heard “horror stories” about PFD from growers.

“This disease has just annihilated their whole crop for next year that they won’t even have anything to pick,” said Beer. “And you can see how bad it is on just this one tree.”
Grower Bryan Beer at one of the orange groves he manages in Southwest Florida.

Beer grabbed an orange tree branch and pointed to what’s called a “button.” When the orange falls off, it leaves what the fruit would normally be attached to. He said it’s a sign the tree is in trouble.

University of Florida researcher Megan Dewdney has studied citrus trees for nearly a decade. She said there’s a combination of factors contributing to the current fungal spread in Florida.

For one, the orange trees are already stressed from battling the citrus greening disease, so they’re blooming at odd times. And then El Niño brought more rain than normal for winter. Dewdney said the unusual blooms plus unusual rains allowed the fungus to thrive.

“The flowers were stimulating a small amount of the fungus ‘til the major bloom showed up and then that coincided with the El Niño patterns of wet, cool-ish winter, which was perfect for the fungus,” she said.

Dewdney said this is a widespread problem throughout the state. But she said we won’t know the extent of crops lost until the summer.

Local grower Bryan Beer said he thinks it’s going to be “very, very, very bad.”

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  • GM banana resistant to fungus shows promise

[KAMPALA] A banana strain resistant to a common fungal disease could help smallholder farmers in East Africa better control the crippling disease, which has been spreading across the region over the last three decades.

The results of confined field trials of a genetically modified (GM) banana with improved resistance to a black sigatoga disease, the devastating leaf spot fungus, are promising, researchers have told SciDev.Net.

The disease is caused by the fungus Mycosphaerella fijiensis and it can halve fruit production in affected plantations. It is easily spread by airborne spores, rain, planting material, irrigation water and packing material used in transporting goods between banana-growing countries.

The dark leaf spots caused by the fungus eventually enlarge and merge together, causing much of the leaf area to dry.

The team led by Andrew Kiggundu — head of banana biotechnology research at the Uganda’s National Agricultural Research Laboratories Institute (NARL) in Kawanda — analysed 19 lines of GM bananas and found promising results in five of them. Andrews told SciDev.Net further research is needed to calculate the exact yield gains from using the resistant banana strain.

The researchers inserted genes for chitinase — an enzyme that breaks down chitin, the hard substance that makes up the cell walls of the invading fungi — preventing the fungus from invading the plant cells and causing the disease.

Kiggundu said laboratory tests using leaves from transgenic plants showed almost full immunity when cultured fungi were applied to the leaves.

Researchers collaborated closely with the Catholic University of Leuven in Belgium, where several banana lines were engineered to include the chitinase gene before being brought to NARL for testing.

However, Settumba Mukasa, resident banana expert in the department of crop science at Uganda’s Makerere University, said the field trials had more significance for building research capacity in Uganda than the development of a new disease-resistant banana.

“[The project] is a stepping stone for subsequent breeding programs and genetic engineering programmes. As a consequence of this project we can now do transformations of other varieties of bananas and other crop species,” said Mukasa.

While black sigatoka is among the top three diseases affecting bananas in Uganda it mainly affects Cavendish, which are not as widely cultivated as other types of bananas.

But for the few farmers in Uganda who do grow Cavendish bananas, the development may be useful since the disease is currently controlled by aerial pesticide spraying which is expensive for smallholders and affects their health.

“Farmers cannot afford that because they are small and they have few plants. Here, chemical control is not viable, so this approach may be the only available method to manage the disease,” Mukasa said.

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  • Fungus-resistant gene found in rice


Scientists in Japan have found a way to create high-yielding rice with long-lasting resistance to the devastating rice blast fungus.

Sufficient rice to feed 60 million people is destroyed by the blast fungus, Magnaporthe grisea — also known as Magnaporthe oryzae — every year.

Some rice is naturally resistant but is often also of lower yield. Now a team led by Shuichi Fukuoka from the National Institute of Agrobiological Sciences in Japan has engineered good quality rice that is both resistant to blast disease and high-yielding.

Their research was published in Science last week (21 August).

By comparing japonica rice that is resistant to blast disease with rice that succumbs to infection, Fukuoka found that a change in a key gene called Pi21 can mean the difference between devastating infection and mild disease.

Fukuoka says even plants with the resistant form of the gene become infected, but “The damage they suffer is not so serious, making it possible to reduce the amount of fungicide used by 50 per cent.”

He says his team’s findings will be particularly useful in mountainous areas where blast disease is a serious threat.

There have been many previous attempts to engineer resistant rice strains by making specific adjustments to plant immunity to allow the plants to recognise and resist the fungus.

But according to Nick Talbot, professor of molecular genetics at Exeter University in the UK, many of these modifications have a field life of just 2–3 years, as the fungus is quick to find ways to circumvent them and avoid being recognised.

Having the resistant form of Pi21, however, means a plant increases its defences against infection in general, making it much harder for the blast fungus to find a way to take hold, says Talbot.

He says the Japanese researchers have made a big discovery with universal applicability. When this is combined with other methods of engineering rice, scientists may be in a position to “exclude blast infections in a durable manner”.

Fukuoka has also managed to isolate the resistant form of Pi21, meaning it can be separated from other genes associated with poor yield. Previously this has been difficult because when scientists have tried to transfer the resistant Pi21 gene into new strains of rice, the genes affecting quality have also hitched a ride.

Fukuoka says the fact that his research has shown the exact location of the Pi21 gene means scientists can ensure it is not replaced by a more vulnerable form when breeding new rice strains.

Link to full article in Science


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12:00 AM, March 01, 2016 / LAST MODIFIED: 03:44 AM, March 01, 2016

‘Wheat blast’ threatens yield

Farmers in 6 districts complain of infection

Wheat blast disease has become a serious threat to grain quality and yield, incurring losses to the farmers in six southwestern districts.

Scientists and specialists after laboratory tests claimed that this is the first time in Bangladesh in which the seasonal crop got infected with this disease.

Officials at the Department of Agricultural Extension (DAE) and Wheat Research Centre (WRC) of the Bangladesh Agricultural Research Institute said they have examined samples from the fields and confirmed that the disease is a blast infection.

They identified the fungus that might have grown due to unexpected temperature fluctuation and several days of continuous rain in the first week of February.

Experts also have tested the seeds used to be sure of the infection, the officials said.

The affected districts include Kushtia, Meherpur, Chuadanga, Jhenidah, Jessore, and Magura.

DAE officials, who visited the affected fields, said Meherpur was the badly hit. Around 2,000 hectares of wheat fields had been damaged by the fungus.

According to farmers, they have marked yellow and black spots on the leaves and sheaves of wheat. After a few days, the spots got larger and spread over the entire plant.

At one stage, both the sheaves and flowers turned yellow and white, and finally the plant dried up without producing any grain.

Mustafizur Rahman, deputy director of Meherpur DAE, said farmers started informing them about the matter from mid-February.

“We told the higher authorities about the problem after visiting the fields,” he said.

A team, led by Paritosh Kumar Malaker, chief scientific officer of Wheat Research Centre in Dinajpur, visited the affected fields in Meherpur, Chuadanga, and Jhenidah on Wednesday.

“We have made pathogen tests using the diagnostic technique, called ‘field pathogenomics’, and confirmed the symptoms of the disease,” he said.

He said, “As it [disease] is the first infection in Bangladesh, we need to be more careful.”

Farmers and DAE officials said the areas experienced rain in the first week of February. After five to seven days, farmers observed spots on wheat leaves and sheaves.

This correspondent visited Garadoba, Saharbati, Dhankhola, Bamundi of Gangni upazila, and Khoksa, Chandbeel, Madandanga in Meherpur Sadar upazila and found a large number of affected fields.

Farmers Ripon and Mawla Boksh of Madandanga told this correspondent that they jointly cultivated wheat on five bigahs of land. About half of the crop was damaged. They have to incur a huge loss, they said.

Sources at the DAE divisional office in Jessore said farmers in the six southwestern districts cultivated wheat on around 58,135 hectares. Some 16,710 hectares are in Kushtia, 10,320 hectares in Jhenidah, 7,020 hectares in Magura, 5,810 hectares in Chuadanga, 4,400 hectares in Jessore and 13,875 hectares in Meherpur.

Mustafizur Rahman, deputy director of Meherpur DAE, said they were holding meetings with the farmers and distributing leaflets to create awareness among the farmers.

The DAE office also advised the farmers to spray Nativo and Folico on the affected fields.

He primarily estimated that 5 percent of the total production might be affected.

However, Chief Scientific Officer of WRC Paritosh Kumar said wheat production would decrease by around 10-40 percent.

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Florida Farmers Adapting to UF/IFAS Web-Based Tool to Ward Off Strawberry Diseases

Released: 16-Feb-2016 8:05 AM EST
Source Newsroom: University of Florida Institute of Food and Agricultural Sciences


Newswise — GAINESVILLE, Fla. — Farmers are adapting to a UF/IFAS-developed, web-based monitoring system that can help the environment by using less chemical treatment to prevent strawberry diseases, which will help the state’s $306 million a year crop, a new UF/IFAS study shows.

The web-based tool, known as the Strawberry Advisory System (SAS), uses data such as temperature and leaf wetness to tell growers when to spray fungicide to ward off diseases.

“Overall, the results show evidence of potential economic gains from switching from calendar to certain SAS-based options,” said post-doctoral researcher Theodoros Skevas, who led the study.

Most strawberry growers treat for fungi every week. Natalia Peres, a UF/IFAS associate professor of plant pathology, helped develop the SAS in 2012 to give producers more precise times to chemically prevent two potentially deadly fungi. The SAS has two models, one to help farmers control Botrytis and the other to prevent anthracnose – two fungi that make the fruit rot.

For a new study published in the journal Crop Protection, the team of University of Florida Institute of Food and Agricultural Sciences researchers examined the economic effects of traditional, calendar-based chemical treatments of strawberries and compared them to variations of the SAS, using different chemicals.

In order to compare the calendar-based system and the web tool, Skevas used production yields and costs, and historical strawberry prices (i.e. from 2000 to 2015) to construct simulated budgets. The historical strawberry prices helped to account for price volatility when measuring the economic performance of the calendar and SAS-based systems with different chemical treatments. They found that treatments following SAS recommendations with some products posed no greater risk than applying fungicides weekly. But, the risk and economic performance depended on the choice of product used.

A UF/IFAS study published in 2014 showed the SAS can bring growers $1.7 million more in net profits over 10 years than a calendar-based fungicide system because it guides growers to spray their crop at optimal times. Skevas said the latest study offers more precise product recommendations on which SAS-based systems growers would have better economic performance and reduced risks under different botrytis fruit rot conditions.

Peres and Zhengei Guan, an assistant professor of food and resource economics, supervised Skevas’ research. All three conduct research at the UF/IFAS Gulf Coast Research and Education Center in Balm, Florida.

Before SAS was developed, strawberry farmers traditionally sprayed weekly during the November-to-March growing season. Spraying more often than needed increases production costs and can lead to fungicide resistance, Peres said.

By: Brad Buck, 352-294-3303, bradbuck@ufl.edu
Sources: Theodoros Skevas, 813-633-4128, skevast@ufl.edu
Natalia Peres, 813-633-4133, nperes@ufl.edu


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