Late Blight Disease

18th July, 2024 Agriculture

Late Blight Disease

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Context

The Central Potato Research Institute (CPRI) has issued an advisory for potato farmers, warning of a high risk of late blight disease in the crop due to changing weather conditions.

Late Blight Disease

Late blight disease, is a fungal infection caused by Phytophthora infestans.
The primary host is potato, but infestans also can infect other solanaceous plants, including tomatoes, petunias and hairy nightshade.
It poses a significant threat to potato crops. This disease can lead to substantial yield losses and diminish the quality of tubers.
Cool, moist weather conditions are highly favorable for the spread of late blight.

Importance of Proactive Management

Late blight disease can cause substantial damage to potato crops, and timely management is crucial to prevent its spread.

Advisory by Central Potato Research Institute (CPRI) for Fungicide Application

Preventive Measures

Farmers who have not yet sprayed fungicide on their potato crops or whose crops are not yet showing symptoms of late blight disease should immediately spray fungicide containing mancozeb chlorothalonil at the rate of 0.2%.
This involves dissolving 2 kg of the fungicide in 1,000 liters of water per hectare.

Curative Measures

In fields where symptoms of the disease have already appeared, farmers are advised to use specific fungicide combinations:

Cymoxanil + Mancozeb: Apply at a rate of 3 kg per hectare (1,000 liters of water).
Fermion + Mancozeb: Apply at a rate of 3 kg per hectare (1,000 liters of water).
Dimethomorph + Mancozeb: Apply at a rate of 1 kg of dimethomorph and 2 kg of mancozeb per hectare (total mixture 3 kg) with 1,000 liters of water.

Repeating Fungicide Application

The advisory emphasizes the importance of repeating fungicide spraying at intervals of 10 days, depending on the intensity of the disease.
Farmers are cautioned against the repeated use of the same fungicide and advised to use a sticker (0.1%) along with the fungicide to enhance its effectiveness.

Proper Drainage and Weed Control

In addition to fungicide application, the CPRI advisory highlights the need for proper drainage in fields and the prevention of weed growth.
Weeds can harbor the disease-causing fungus, increasing the risk of infection in potato crops.
Timely management of late blight disease is critical to prevent significant yield losses and ensure a healthy potato crop.

Himachal Pradesh: A Major Hub for Potato Production

Himachal Pradesh has emerged as a significant hub for potato production in India, covering approximately 14,685 hectares. Potatoes account for about 20% of the total vegetable cultivation area in the region.
The state's climatic conditions, characterized by a cool temperate climate, high wind velocity, and moderate humidity, provide an ideal environment for cultivating disease-free, high-quality potato seeds and table potatoes.

Low Aphid Population

The low aphid population in Himachal Pradesh contributes to the production of disease-resistant potatoes, making the state a prime location for seed potato production.
The state's potatoes are known for their high dry matter content, reaching up to 20%, which is essential for producing quality chips.

Timing of Potato Harvest

The timing of the potato harvest in Himachal Pradesh is advantageous, with around 80% of the cultivated area relying on rainfed agriculture.
Potato cultivation is predominantly managed by small and marginal farmers, making it a lifeline for many in the state.

Lahaul Valley: A Key Area for Potato Production

The Lahaul Valley, a cold desert in Himachal Pradesh, is a significant area for potato production.
The valley specializes in cultivating prized seed potato varieties like Kufri Chandramukhi, Kufri Jyoti, Table Santana, and Shafordi, which are favored for chip production.

Potential for Growth and Food Security

Experts highlight that Himachal Pradesh's potato production has immense growth potential and can contribute significantly to the country's food security.
By following the CPRI advisory and adopting proactive measures, farmers can protect their crops from late blight disease and ensure a bountiful harvest.

Central Potato Research Institute

The Indian Council of Agricultural Research -Central Potato Research Institute (ICAR-CPRI), located in Shimla, Himachal Pradesh, India, is a public non-profit research institute dedicated to potato research. As an autonomous institute under the Indian Council of Agricultural Research, Ministry of Agriculture and Farmers' Welfare, Government of India, ICAR-CPRI was established in August 1949 in Patna, Bihar, based on the recommendation of Sir Herbert Steward, the then-Agricultural Advisor to the Government of India. Its primary objectives include developing potato varieties, expanding potato cultivation, and creating cultivation techniques suitable for local conditions. In 1956, the institute was relocated to Shimla to enhance hybridization work in potato breeding and maintain seed potato health. It came under the aegis of the ICAR in April 1966.

Bacterial Plant Diseases

Disease Name	Plant Affected	Causal Organism	Symptoms
Granville wilt	Tobacco, tomato, potato, eggplant, pepper, and other plants	Pseudomonas solanacearum	Stunting, yellowing, wilting of parts above ground, roots decay and become black or brown
Fire blight	Apple and pear	Erwinia amylovora	Blossoms appear water-soaked and shrivel
Wildfire of tobacco	Tobacco	Pseudomonas syringae	Yellowish green spots on leaves
Blight of beans	Beans (common blight)	Xanthomonas campestris	Yellowish green spots on leaves
Soft rot	Many fleshy tissue fruits such as cabbage, carrot, celery, onion	Erwinia carotovora	Soft decay of fleshy tissues that become mushy and soft
Crown gall	More than 100 genera of woody and herbaceous plants	Agrobacterium tumefaciens	Stems and roots becoming wrinkled and turning brown to black
Aster yellows	Many vegetables, ornamentals, and weeds	Mycoplasma-like organism (MLO)	Chlorosis, dwarfing, malformations
Citrus stubborn disease	Citrus and stone fruits and vegetables	Spiroplasma citri (MLO)	Chlorosis, yellowing of leaves, shortened internodes, wilting

Fungal Plant Disease

Disease Name	Plant Affected	Causal Organism	Symptoms
Late blight of potato	Potato	Phytophthora infestans	Water-soaked dark green to black or purplish lesions with pale green margins on lower leaves, white mildew at the edge of lesions
Chestnut blight	Chestnut tree	Endothia parasitica	Yellowish to reddish-brown patches appear on the bark, lesions spread quickly and girdle twigs or limbs, which die
Dutch elm disease	Elm tree	Ceratocystis ulmi	Leaves wilt, turn dull green to yellow or brown and drop off, branches die
Black stem rust of wheat	Wheat and many types of grass	Puccinia graminis	On wheat, rust-coloured pustules with spores, chlorosis of surrounding tissue, followed by the development of black teliospores; on barberry, chlorosis and hypertrophy of infected tissue, orange spore masses
White-pine blister rust	White Pine tree	Cronartium ribicola	Small, discoloured, spindle-shaped cankers surrounded by a narrow band of yellow-orange bark, blisters exude secretion followed by bright orange pustules
Corn smut	Corn	Ustilago maydis	Minute galls form on young corn seedlings; on older plants, large galls are produced on the silk of ears and on tassels, leaves, and stalks
Loose smut	Barley, oats, wheat	Ustilago nuda	Infected heads are covered with masses of olive-green spores
Downy mildew	Many types of plants: grapes, grasses, vegetables, and others	many species of the family Peronosporaceae	Yellow irregular spots appear on the upper leaf surface, downy fungus growth appears on the underside
Black spot of rose	Rose	Diplocarpon rosae	Large circular black lesions on leaves, leaves turn yellow and fall off
Anthracnose of grape	Grapes	Elsinoe ampelina	Same as the black spot of rose
Nectria canker	Apple and pear and many hardwood forest trees	Nectria galligena	Initially, small circular brown areas enlarge and become depressed with raised edges, callus tissue produced around the canker
Black knot of plum and cherry	Plum and Cherry	Plowrightia morbosum	Small black knotty swellings on twigs and branches
Soft rot	Flowers, fruits, and vegetables with fleshy organs	Rhizopus species	Tissues become soft with a water-soaked appearance that often spreads rapidly, followed by the development of fuzzy grey mycelium and black spores
Fusarium wilt of tomato	Tomatoes	Fusarium oxysporum	Leaves are bent down, growth is stunted, dark streaks appear in vascular tissue

Plant Diseases caused by Viral and Viroids

Disease Name	Plant Affected	Causal Organism	Symptoms
Tobacco mosaic	Tobacco, tomato, and hundreds of other vegetables and weeds	Tobacco mosaic virus (TMV)	The mottled appearance of leaves (mosaic pattern), dwarfing
Cucumber mosaic	Cucumber, bean, tobacco, and other plants (wide range of hosts)	Cucumber mosaic virus (CMV)	Similar to those of TMV infections
Barley yellow dwarf	Barley, oats, rye, wheat; also pasture grasses and weeds	Barley yellow dwarf virus (BYDV)	Yellowing and dwarfing of leaves, stunting of plants
Tomato spotted wilt	Tomato, pepper, pineapple, peanut, and many other plants	Tomato spotted wilt virus (TSWV)	Leaves show concentric, necrotic rings; necrotic region yellow, then turning red-brown
Prunus necrotic ring spot	Stone fruits—e.g., cherry, almond, peach, apricot, plum, and others	Prunus necrotic ringspot virus (PNRV)	Delayed foliation, leaves on infected branches show light green spots and dark rings
Potato spindle tuber	Potato and tomato	Potato spindle tuber viroid (PSTV)	Stunted growth, tubers are spindle-shaped, smaller than healthy tubers
Citrus exocortis	Orange, lemon, lime, and other citrus plants	Citrus exocortis viroid (CEV)	Infected trees show vertical splits in the bark, thin strips of partially loosened bark

PRACTICE QUESTION

Q. Mancozeb and Chlorothalonil are primarily used in agriculture as:

a) Insecticides

b) Fungicides

c) Herbicides

d) Soil conditioners

Answer:

b) Fungicides

Explanation:

Mancozeb and Chlorothalonil are fungicides commonly used in agriculture to control fungal diseases in crops. Fungicides specifically target fungal pathogens and are crucial for maintaining crop health and productivity.

SOURCE: THE HINDU

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