EARLY BLIGHT OF POTATO

POTATO

•A member of the Solanaceae family, the cultivated potato (Solanum tuberosum) is closely related to the tomato, pepper, and eggplant.

•Indians in Peru were the first people to cultivate the potato over 4000 years ago

•The potato, a name derived from the American Indian word “Batata”, was introduced to Europeans be Spanish conquerors during the late 16th Century

•A potato is about 80% water and 20% solid.

•The average American eats 140 pounds of potatoes per year. Germans eat more than 200 pounds per year. 

  Nutritional value per 100 g

Carbohydrates      19 g

Starch    15 g

Dietary fiber   2.2 g  

Fat  0.1 g

Protein  2 g

Water  75 g

Thiamin (Vit. B1)   6%

Riboflavin (Vit. B2)    2%

Niacin (Vit. B3)   7%

Vitamin B6    19%

Vitamin C    33%

Calcium    1%

Iron    14%

Magnesium   6% 

Phosphorus   8%

Potassium   9%

Sodium    0%

EARLY BLIGHT OF POTATO

•Symptoms:

The initial symptoms appear in the form of small, isolated scattered pale brown spots on leaves with deep greenish-blue fungal growth of fungus. The lower leaves are attacked first and then the disease progresses upwards.

In the necrotic tissue, concentric ridges develop, which give a target board effect.

The stem lesions often girdle it and cause “Collar-rot” in young seedling plants leading to collapse of branches or entire above ground portion.

On tubers the affected region is darker than the healthy area and the lesion soon shrinks slightly as dry, corky rot develops.

Causal organism: Alternaria solani
Disease Cycle:

Mycelium and conidia can survive in plant debris and on seed tubers.

The conidia germinate in moist weather and cause primary infection directly or through stomata, first on lower and then on upper leaves.

The secondary infection takes place through conidia carried by wind, water or insects.

Epidemiology

The optimum temperature for conidial germination is 28-30ºC.

If season starts with abundant moisture and frequent rains, disease becomes serious, followed by warm and dry weather, which is unfavourable for the host but helps rapid disease development. Weaker plants are more susceptible.

CONTROL

Crop rotation and field sanitation is a rational measure to avoid primary infection from spores that have survived from previous crop.

Fungicidal sprays starting from 30 days after sowing at an interval of 10-21 days (depending upon the intensity of disease). For this purpose, Dithane M-45 (0.6%), Daconil (0.3%), Acrobat MZ, Ridomil Gold MZ, Banko (0.2 – 0.25%) can be used.

Proper fertilization of the crop to maintain the plant vigour