CONTEXT: The Central Potato Research Institute (CPRI) recently issued an advisory for potato farmers across the country, warning of a high risk of late blight disease in the crop due to changes in weather conditions.

What is Late Blight Disease?

Late blight is a disease that affects potato plants as well as tomato, this disease mostly attacks on tubers of the potato plant and the fruits, leaves or stem of the tomato plant.

Blight is of two types:

1. Early Blight

• Early blight is a disease that infects potato, tomato, some of the mustard and many of salacious crops which is caused by fungus, Alternaria soliani.
• They are miniature, black, and scaly dards that transform into brownish-black, round to oval lesions over time. The specific area of the leaf together with veins results in the yellowing and subsequent death of the affected leaf.




• They can also infect tubers mostly appearing as dark, circular to irregular in shape.
• The disease is considerably more resistant against being rotted by secondary organisms.
• Measures that can be taken to avoid early blight on plants are making sure of good plant health, avoid watering the plants with water droplets falling directly on the plant, and avoid using fields that were used for growing potatoes or tomatoes in the previous season.
• Adequate nitrogen and low phosphorus levels can decrease the intensity of diseases of growth.

2. Late Blight

• Late blight is caused byfungiPhytophthora infestans and is mostly seen in potato and tomato plant.
• First detected in Europe and US in 1830s it was the cause for Irish Potato famine in the 1840s.
• The disease was controlled in the 1880 when the discovery of fungicide that killed the disease was made.




• In this Potato stems are not attacked, but on susceptible varieties the tuber can be invaded resulting in a tan-brown, dry, granular rot.
• Disease identification can be done by identifying the colour that may vary from white to cream colour or during wet period seeing mycelia growth on the back side of the leaves.
• The precautionary measures include growing on disease-free seed potatoes, avoiding source of compost piles, eradication of volunteers, planting with soil cover, removal of infected tubers before storing and killing the vines prior to the harvest.
• There are resistant varieties of crops but some fungicides need to be used even on the resistant varieties of cultivars.

What is a fungus or Fungi?

Types of Fungi

• Yeasts: A type of fungi that has a single cell, and widely used in the production of bread and beer products because of the activity for the synthesis of sugars.
• Molds: Organisms that exists as large structure called hyphae and are classified as being more complex than single celled organisms but are not as complex as plants or animals. It prefers to dwell in various structures depending on the trophic level but commonly infests decaying organic material.
• Mushrooms: Some of the familiar types are the mushrooms; the fruiting bodies of certain fungi, which are mostly edible and are usually isolated from the soil or decaying wood.
• Rusts and Smuts: Ectosomatic parasites mostly known to infest plants leading to diseases those are disastrous to crops.
• Mildews: Like the molds, these fungi often develop on plants and other organic matter, and are destructive to them.

What is a Fungicide?

Fungicides are defined as chemical products that are used to either eradicate fungi or limit fungi and spores’ development. They are mainly used in Crop protection since fungi are likely to cause substantial crop losses such as rusts, mildews, and blights. Mold and mildew can also be controlled using fungicides at parts where they are likely to thrive.

Types of Fungicides

• Contact Fungicides: These are exterior ones and guard the plant just only at the point where they were sprayed or placed or came in contact with fungi.
• Translaminar Fungicides:these are more effective as if miss some parts they can reach there too. These can move from the upper side of the leaf which was sprayed to the lower side of the leaf which was left unsprayed.
• Systemic Fungicides: These are absorbed up by the plant and translocate to the various tissues of the plant to work like an internal shield.

CPRI (Central Potato Research Institute)

• Historical background: The Indian Council of Agricultural Research Central Potato Research Institute-CPRI was set up in August 1949 at Patna Bihar, (now it is relocated to Shimla) on the advice of Sir Herbert steward the Agricultural advisor to Government of India under Ministry of Agriculture and Farmers Welfare Government of India.
• Office:Bemloe, Shimla (Himachal Pradesh)
• Aim: Carry out potato related research, extension and education in collaboration with the national and international institutions to enhance production for sustainable food and nutrition security and poverty reduction in the rural areas.
• ICAR-CPRI, in other words the Indian Council of Agricultural Research, Central Potato Research Institute is a scientific organization under the research wing of the Indian Government which is solely dedicated to the study and advancement of the potato crop.
• Several years ago the institute has initiated the dissemination of practices of marketing the potato in a subtropical region.
• Biotechnology, genomics, genetics and plant breeding, plant protection, soil science and agronomy, plant physiology, biochemistry, and post-harvest technology based modern instrumental facilities have been developed in the institute.



Advisory issued by CPRI regarding the Late Blight Disease

• Potential potato growers who have not applied fungicide for potato or those who have no sign of late blight diseases in their field should use mancozeb chlorothalonil at a cost of 0. 2% to disease-susceptible cultivars.
• Some examples for conventional practices are: application of 2 Kgs of medication per hectare which is dissolved in one thousand liters of water.
• For moderate to high fields where the disease sign has occurred farmers should spray with cymoxanil + mancozeb, fermion + mancozeb, or dimethomorph + mancozeb.
• The recommended rate of cymoxanil + mancozeb and fermion mancozeb as a powder at 3 kg/ha in 1000 L water, while in aqueous solution, dimethomorph with mancozeb is one kilogram of dimethomorph, and mancozeb is 2 kg (total 3 kg/ha in 1000 Litres water).

Varieties of Potato as given by The CPRI and its characteristics: