Showing posts with label Plant Diseases. Show all posts

How To Control Black Spot Of Roses

Posted by Unknown in Flower, Plant Diseases, Rose on Sunday, 12 May 2013

Plant Pathology Infobytes

Gardeners who want to keep their rose garden the envy of the neighborhood should plan to keep black spot fungus disease under control. Black spot is rose "public enemy number one" and commonly makes its appearance in the spring following warm, wet weather.

Symptoms of black spot begin on leaves as small, pin-head sized black or dark brown spots which are circular in shape. The spots increase in size, and infected leaves eventually turn yellow and fall from the plant.

Continued plant attack by black spot results in unattractive foliage as well as reduced size, number, and quality of blooms. Successive seasons of defoliation weakens plants and increases susceptibility to winter kill and other disorders.

Black spot usually occurs on the lower portion of the rose bush first and moves upward as the season progresses. Leaves are most susceptible to infection when young but can be invaded at any point of development during periods when showers are numerous.

Rose varieties vary in susceptibility to the black spot fungus. Grandiflora and floribunda types are generally more resistant than hybrid tea varieties, and gardeners who have hybrid teas in their planting should plan to carry out a full-season black spot control program. The following control guidelines are suggested.

When watering overhead, do so early in the day so that plants have a chance to thoroughly dry before nightfall. Since moisture on leaves is necessary for infection to take place, this cultural procedure is very important in cutting down on foliage infection.
A regular fungicide spray program throughout the growing season is generally necessary to control blackspot.
Most fungicides can safely be combined with insecticides and miticides and will perform better when small amount of spreader- sticker material is added to the spray solution. Dust formulations of rose fungicides generally don't provide the same level of control as liquids.
Regularity of spraying and thorough coverage are important to control. It's important to realize that fungicides protect plants from infection, and once the black spot fungus has invaded foliage, fungicide application is of limited value. For this reason, keep your plants covered with a protective fungicide at all times during the growing season
If only a few leaves show symptoms of black spot, remove and burn them. This will cut down on fungus spread to healthy foliage. Remove all diseased leaves from around the plants in the fall and destroy.
New plantings should be in areas with good air circulation to promote rapid drying of leaves. Also, avoid shady areas and dense plantings where high humidity problems are most likely to occur.

Just how important is rose disease control? Any successful grower will tell you, "Don't even think about growing roses unless you are willing to devote special attention to the control of diseases and other pests." Yet, for individuals who are truly fond of roses, the pleasure of producing their own blooms will justify the time and expense required to keep disease problems to a minimum.

For additional information on blackspot and other rose diseases, check with us at your county Extension office.

Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.

Wheat Disease Threatens Global Food Supplies

Posted by Unknown in Plant Diseases, Research and Studies, Wheat

By Miriam Hall

An international team of researchers has warned that a destructive wheat disease could threaten global food security and is calling for a doubling in funding to develop disease-resistant varieties.

Wheat stem rust - also known as UG99 - is an aggressive fungus and one of the most destructive wheat diseases.

It was first found in Uganda, but has spread through the Middle East, destroying wheat crops.

CSIRO scientist Darren Kriticos - who authored a report about how to keep ahead of the disease - says the wheat industry has been protected so far by developing resistant varieties.

He says wheat stem rust is a global problem and unless there is a long-term plan, wheat-producing countries - including Australia - will be at risk.

"It's headed for Australia. It's not a matter of if it gets to Australia, it's a matter of when," he said.

"So it's imperative for Australia's wheat production and wheat production security to ensure that we have varieties of wheat that are resistant."

Mr Kriticos wants wheat-producing countries around the world to collectively invest $50 million a year to research new ways to protect crops.

"If that investment isn't made we're going to run into problems," he said.

"There will be outbreaks of new emerging strands so this isn't a problem that we can fix with a one-off investment."

Professor of Applied Economics at the University of Minnesota Phil Pardey agrees that a long-term approach is needed.

"It's not just getting the investments right today; it's keeping them right that's the problem," he said.

"It's trying to get that policy message across that whilst Australia might be carrying its fair share globally, we certainly indicate that research in this area needs to double.

"And if you don't, the natural consequences are you expose yourself to a much higher risk of crop failures."

He says agricultural research and development is not often in the spotlight.

"They're not probably particularly sexy to most people in thinking about [research and development]," he said.

"But when you start paying more for your food at the supermarket, you start to notice. We've seen a major increase in food commodity prices in the last five to 10 years.

"What happens in terms of your food bill on a week-to-week basis at a supermarket directly relates back to the amounts and types of investments in [research and development]."

Farmer Bruce Schwartz - who has grown wheat for decades - has seen first-hand how damaging crop diseases can be.

"The disease problems that we do have change with the seasons," he said.

"They can be really bad one year and not so bad the next."

He keeps a close watch on new varieties as a way of protecting his wheat.

"A lot of money goes into research and development," he said.

"They're trying really hard to find remedies for all these diseases but every time they think they've nearly got there, something else pops up."

The paper warning about the threat of wheat stem rust was published in the journal Science today.

Controlling Powdery Mildew with Homemade Spray

Posted by Unknown in Fungi, Homestead Tips and Tricks, Organic Farming, Plant Diseases on Wednesday, 8 May 2013

If you are seeing powdery-looking patches on the foliage of your plants, you most likely have a case of the very common powdery mildew fungal disease. Here is a simple spray for controlling the spread of the fungus. It won't get rid of the fungus on leaves that already have it, but it will prevent it from spreading to the rest of the plant.

Ingredients:

1 gallon of water

1 tablespoon of baking soda

1 tablespoon of vegetable oil

1 tablespoon of dishwashing liquid

Mix the ingredients together and add them to a spray bottle. Spray your plants weekly, preferably on overcast days to prevent it from burning the foliage.

Revealing of Potato Disease Taking Hold

Posted by Unknown in Plant Diseases, Potato, Research and Technology, Vegetable on Saturday, 26 January 2013

Infectious agents released from the late blight pathogen use a sticky patch of amino acids to adhere to potato plant cells

Late blight is an economically devastating disease for potato farmers worldwide, causing tens of billions of dollars worth of damage each year. Phytophthora infestans, the causal agent of late blight, has evolved to overcome fungicides and major resistance genes that have been bred into commercial potato cultivars (Fig. 1). In order to dampen the immune response of its host, P. infestans secretes molecules called disease effectors at the site of infection.

Now, a research team from Japan and the UK has determined the molecular structure of the disease effector called avirulence protein 3a (AVR3a), which is known to inhibit disease resistance in potato plants1. Understanding the molecular structure and function of AVR3a will help plant biologists to elucidate how P. infestans causes infection so that they can develop better control measures.

Using nuclear magnetic resonance spectroscopy, a technique employed to study the configuration of molecules, the research team—led by Ken Shirasu from the RIKEN Plant Science Center in Yokohama—identified a patch of positively charged amino acids in the structure of AVR3a. The team found the positively charged section of amino acids is conserved among different versions of AVR3a from P. infestans and the model pathogen P. sojae, indicating that this part of the overall structure could be important to AVR3a’s role in the infection process.

By examining potato plants to determine the final destination of AVR3a within the infected host, the researchers found that the disease effector binds to a lipid molecule called phosphatidylinositol phosphate (PIP), which forms part of the structure of the potato cell membrane.

To determine whether the newly identified section of amino acids is essential to PIP-binding, Shirasu and his colleagues generated AVR3a mutants by substituting the positively charged amino acids found in the newly identified section with negatively charged amino acids. Using a binding assay to investigate the interactions between molecules, the researchers showed that the AVR3a mutants are unable to join to PIP and hence attach to the potato cell membrane. They therefore proposed that AVR3a may bind to PIPs in the cell membrane in order to remain undetected by the immune system of the potato.

The team’s next challenge is to determine how AVR3a molecules and other disease effectors from P. infestans translocate into the host from the site of infection. “Developing ways to block the action of AVR3a and other disease effectors will provide means to control this damaging crop disease,” says Shirasu.

The corresponding author for this highlight is based at the Plant Immunity Research Group, RIKEN Plant Science Center

Dalbergia sissoo ‘Sheesham’ disease stages a comeback

Posted by Unknown in Biofuel, Plant Diseases, Sheesham Tree on Monday, 10 September 2012

A healthy Sheesham Treem

TAHLI (Sheesham/ Dalbergia Sissoo) — a high quality broad leaf, dark brown tree about 30 to 45 feet tall — has spread to almost every area located at 120m to 1,250m above the sea level owing to the environment of the sub-continent

Punjab apart, the genus Dalbergia has more than 300 species and many other tropical and sub-tropical areas of Asia, Africa, South Africa, Central America, South America and many more, share the blessings of this luxuriantly growing tree. In Pakistan and most of India, a species-Delbergia Sissoo, also named as Sheesham or Tahli, are in abundance. While, in South East Asia, Dalbergia Cochinchinensis, commonly known as, Trac is found.

Sheesham is a world class timber treasured for its density, colour, elasticity and durability of the wood, which weighs 830kg/m3 on drying. It is used for numerous purposes, ranging from wooden teaspoons to boats, from agricultural implementations to super structures. The multidimensional character of Tahli brings it at par with Deodar (Cedrus Deodara) and Purtal (Abies Pindrow) which meet almost 90 per cent of the commercial, construction and industrial timber needs of Pakistan.

It is a farmer-and-environment-friendly tree by increasing the annual rainfalls, keeping the environment cool, and decreases the ratio of wind evaporation which saves the atmosphere from becoming dry. This provides immunity to inhabitants of such areas from chest and respiratory diseases. The tree helps in stabilizing canal banks and preventing soil erosions. Punjab’s 20.6 million ha of the upper Indus Plain is divided into five forest areas which are riverain, irrigated, scrub, coniferous, and trees on private lands.

Plantations in the irrigated lands began after developing Changa Manga, Mirpur, Daphar, Khanewal, Kamalia, and Cheechawatani. Tahli is a main species of riverain forest. The ratio of Tahli/Mulberry (Morus Alba) here is 27 per cent, poplar one per cent, eucalyptus 23 per cent and others 27 per cent.

Tahli along with mulberry makes about 50 per cent of the plantation with numerous benefits for social, economic and physical environments. Besides, it provides fuel, small timber, manure, leaf, and other economic needs of rural and urban people. The tree shelters insectivorous birds and protects them from winds.

The Chronic Disease

A disease during the last 6/7 years has jeopardized the blessing associated with this tree. Initially a single branch vitiates and then the whole tree goes down unnoticed, unattended, and unheard. According to the Punjab Forest Department’s survey, about 70 per cent of the total trees are affected, out of which two per cent is incurable. Despite numerous Tahlis being vitiating at Mandra on the Grand Trunk Road, the attitude of forest department is unsympathetic.

As the tree takes 30 to 60 years to mature and perhaps the officials are too ambitious to wait and watch it growing once in their life or service-time, they prefer eucalyptus though it has been banned and takes five to seven years for cutting. Same is the attitude towards plantation of indigenous trees such as Keekar, Phulla, Neem, Chahra.

Most officials don’t know about the nature of disease Tahli tree is suffering from. Many humbly admitted their professional limitations while some are aware of it.

This is a ‘diabac disease’ they say. The effected tree starts to vitiate from the top travelling down to roots, says a representative of forest department. In addition he added, the disease is affecting Thali for last 6/7 years. Though it disappeared but is now making a comeback.

A plant pathologist says that the reason for depletion was a fungus that frequently changes hosts and this time it has singled out Tahli. In his opinion verticillium wilt disease is working wherein water and root canal systems of the tree are blocked thus ending the food making processes. The only remedy is to develop a fungus-friendly species of Tahli. Rising temperature in tropical zones also helps in spreading the wilt disease.

A professor from the Agriculture University Faisalabad in 2003 had told this scribe that the Forestry Institute, Peshawar has identified more than 60 pathogenic species of fungus living on Tahlis, and that two to three per cent of the trees in the Punjab were either dead or would wither away soon.

An official from the Forest Office, Rawalpindi said that Tahli in Punjab is fast ebbing and laboratory tests of the parched roots showed rotting of tap and lateral feeding roots, because of the Fusarium fungus.

It may have resulted due to poor drainage and prolonged water-logging during rains. Roots are the most vulnerable part of a tree. In a waterlogged area the chances of fusarium are very high, he said. These dead or drying trees must immediately be felled down to avoid further nesting of pathogens on healthy trees.

Depletion of the tree is endangering the physical, social, and economic environment of the province. Its extinction on a massive scale is certainly pregnant with dangerous consequences for the country both on micro as well as macro levels.

The issue becomes more significant as Pakistan has only 4.2 million hectares of forest area - with per capita forest not more than 0.037 hectare, as against the world average of one hectare. The demand of wood too, is rising by about 10 per cent per year, and Tahli of course is the most sought after furniture wood.

Endangered Tahli must be a revelation for the advocates of eucalyptus monoculture plantations. Might one see how a certain species can take hostage people and the environment? More importantly, consumption patterns for wood and timber among our rural and urban communities need a special deliberation. The traditional self-contained village of Punjab was never an isolated independent entity. A village was a physical stage on which people performed and acted their allocated roles, but the social processes, of which, these people were a part had a broader physical range.

In economic and political terms, they were a part of a greater whole and the whole was greater than the sum of its parts. It was their way of life almost throughout the subcontinent and the cooperation between different strata of society in a village was never organized at a village level, instead at the level of people who shared common economic interests.

For example, to fell a tree in a typical Punjab village was the duty of cobbler, because he needed the upper layer of Keekar tree to colour the shoe leather. Then carpenter sorted out the firewood from the high quality wood for furniture. The firewood was taken into custody of a cook for cooking purposes and fire, so on and so forth - the tree was not the sole property of anyone person or group - luckily there wasn’t any forest department then - almost every member of the traditional rural society had his economic interests associated with a tree.

Owing to its extra qualities Tahli has always occupied the imaginations of the Punjabi poets as women used to sit under a shady Tahli to make a Tranjan (a social gathering of the women of an area to do daily allocated importable routine works).

Things have changed. Cultural lags exits, but should we let our Tahli trees to vitiate. Certainly not; to save our ecology from further degradation, resulting from depletion of Tahli, experts from Faisalabad-based Nuclear Institute of Agriculture and Biology (Niab), the National Institute for Biotechnology and Genetic Engineering (Nibge), Agricultural Universities and Forest Department should work together as some of these departments are already working on it and, we wait for domino effects.

The forest departments should encourage plantation of indigenous trees - Keekar, Phulla, Neem, Chahra. Recently elected Nazims and those who want to empower people at the grassroots level should also encourage plantation of indigenous tree species and they might work in collaboration with the non-governmental organizations working for preservations of environment and development of ecology.

The Dawn

Lack of crop zoning blamed for virus attack on cotton in Pakistan

Posted by Unknown in Cotton, Plant Diseases on Saturday, 8 September 2012

ISLAMABAD: The main reason for repeated attacks of cotton leaf curl virus (CLCV) on farms in Pakistan is lack of implementation of crop zone management laws, leading to a gradual increase in intensity of virus attack on the cotton crop, says a leading cotton ginner.

In a press release, Pakistan Cotton Ginners Association (PCGA) Executive Member Ihsanul Haq blamed the spread of sugar mills in the cotton belt for frequent virus attacks.

He recalled that nearly 15 years ago the Punjab government had declared the districts from Rahim Yar Khan to Mian Channu as cotton zone and discouraged establishment of new sugar mills or capacity enhancement of existing mills there in a bid to avoid humidity buildup, which could damage the cotton crop.

However, he said, the setting up of new sugar mills and doubling of capacity of running mills continued on political considerations, which brought an extended area under sugarcane crop and increased humidity in adjacent localities, creating a favourable environment for virus attack on cotton crop.

“If the present trend continues, then heavy attack of virus on cotton may result in severe yield losses,” he warned.

According to Haq, among all cotton-producing countries of the world, virus attack occurs only in Pakistan and the adjacent Indian Punjab. Other countries have controlled the virus with better management practices.

This year, the International Centre for Agriculture in Dry Areas has provided seeds for 1,385 cotton varieties to Pakistan for screening traces, if any, of cotton leaf curl virus at Multan and Sakrand cotton research institutes of the Pakistan Central Cotton Committee (PCCC).

However, so far less than 400 seeds have been found free of cotton virus and among them less than 20 are said to be of acceptable agronomic value.

“Without following proper crop zoning for cotton, the virus attack can’t be controlled,” Haq said. The areas free from sugarcane crop like Cholistan are seldom attacked by the virus.

Farmers have been advised that in case of virus attack, they should spray potassium nitrate (1kg per acre) in combination with Vitamin C (2,000mg per acre) and growth-regulating hormone twice or thrice to save the crop.

The Express Tribune

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