Late blight of potato is one of the most important disease faced during the cultivation of potato
Which is the causal organism of Late blight of potato?
A fungus named Phytopthora infestans is the causal organism of Late blight of Potato.
How is the disease cycle of Late blight disease?
What are the symptons of Late blight of potato?
It affects leaves, stems and tubers.
Water soaked spots appear on leaves, increase in size, turn purple brown & finally blacken.
White growth develops on under surface of leaves Which spreads to petioles, rachis & stems.
It frequently develops at nodes.
Stem breaks at these points and the plant topples over.
In tubers, purplish brown spots and spread to the entire surface on cutting, the affected tuber show rusty brown necrosis spreading from surface to the center.
What are the characteristic features of fungus causing Late blight disease?
The mycelium is endophytic, coenocytic and hyaline which are inter cellular with double club shaped haustoria type.
Sporangiophores are hyaline, branched intermediate and thick walled.
Sporangia are thin walled, hyaline, oval or pear shaped with a definite papilla at the apex.
The sporangium may act as a conidium and germinate directly to form a germ tube.
Zoospores are biflagellate possess fine hairs while the other does not.
What is the Mode of spread and survival of fungus causing Late blight disease?
The infected tubers and the infected soil may serve as a source of primary infection.
The diseased tubers are mainly responsible for persistence of the disease from crop to crop.
The air borne infection is caused by the sporangia.
What are the Favourable conditions for the spread of Late blight of Potato?
RH->90%, Temp.-10-25°C and Night temperature of 10°C are favourable for the spread of disease.
Cloudiness on the next day and Rainfall at least 0.1mm, the following day.
What are Management practices of Late blight of potato?
A regular spraying and dusting during the growing season give effective control.
First spraying should be given before the commencement of the disease and subsequent should follow at reqular interval of 10 -15 days.
Protective spraying with mancozeb or zineb 0.2 % should be done to prevent infection of tubers.
Destruction of the foliage few days before harvest is beneficial and this is accomplished by spraying with suitable herbicide.
Tuber contamination is minimized if injuries are avoided at harvest time and storing of visibly infected tubers before storage.
The resistant varities recommended for cultivation are Kufri Naveen, Kufri Jeevan,
Kufri Alenkar, Kufri Khasi Garo and Kufri Moti.
Further readings and references
Plant Pathology by GN Agrios