It is a very serious disease of banana in the north eastern region, especially in Jahaji and Champa varieties. This disease is caused by a virus which is transmitted by an aphid (Pentalonia nigronervosa). In the affected plants, leaves become short and bunch together at the top of the pseudostem to form a rosette. Growth is stunted and fruit production fails. Once a plant is attacked by this virus, it cannot be cured. However, other plants can be prevented from having it by removing and destroying the infected plants along with their rhizomes and spraying systemic insecticides like metasystox or Dimecron at the rate of 0.1-0.5 percent on the healthy plants to kill insect vector. Strict quarantine regulations should be followed in disease free areas.
Panama disease (Banana wilt)
This is a soil borne fungal disease caused by Fusarium oxysporum F. cubense. Progressive browning and falling of leaves and appearance of black streaks on underground stems are the characteristic symptoms. Control measure is to remove infected plant parts, and application of 0.5-1 kg of lime in each pit. Soil drenching with fungicide vapour (850g in 100 litre of water) and mercuric chloride (3000 ppm) or 1 percent solution of formathion gives effective results. Highly infected soils should not be replanted with banana at least for 3-4 years.
It is caused by the fungus Mycosphaerella musicola. Light yellow to brown leaf spots occur, usually starting from margins and spreading inwards parallel to the veins. Infection occurs through stomata of young leaves. It can be controlled by spraying with (0.2%) blitox, dorsal, falcidin and Bavistin. Two percent linseed oil and Bordeaux mixture has been found to reduce the incidence of this disease.
It is also fungal disease caused by Botryodiplodia, Gloeosporium and Fusarium spp. the disease is characterized by the presence of heart leaves with part of the lamina missing or decayed. In severe cases, the inner leaves of the crown first turn yellow, then brown and finally die. To prevent spread of disease, spraying of captan or Dithane M-45 or Dithane Z-78 is effective.
Main stalk rot
A black soft rot begins at the proximal end of the main stalk of the bunch. Affected parts shrivel and dry up. Premature ripening of fruits often occurs when stalk rot is severe. It can be controlled by spraying of Dithane M-45 or Dithane Z-78.
Pitting disease (Pyricularia grisea)
Round sunken pits appear on the fruit as it approaches maturity or may also appear after harvesting. The centre of the pit may split the fruit skin. It can be easily prevented by regular weekly spraying of Dithane M-45.
Brown spot (Cercospora hayi)
Brown spots occur on the rachis and fingers. The spots are pale to dark brown with irregular margins surrounded by water soaked tissue. The control measure is same as that of pitting disease.
Stem borer (Odoiporus longicollis)
This is a very serious insect-pest which bores through the sheaths, eats into the pseudostem and also into the rhizome causing considerable damage in certain varieties like Champa, Malbhog, and sometimes Jahaji, in this region. Treatment with celphos at the rate of 3 tablets per plant can effectively control this pest. The larvae of Cosmopolites sordidus also bore into the underground rhizomes and weaken the plants.
Fruit and leaf beetle (Colaspis hypochlora)
It feeds on the epidermis of leaves, skin of young fruits and inflorescence, causing corky tissues to develop on the surface of the fruits and leaves. Severe scarring of fruit skins leads to the production of underdeveloped fruits which fetch fewer prices in the market. Malathion (0.05%) sprays just before and after opening of the inflorescence can control this pest.
Banana aphid (Pentalonia nigronervosa)
This insect is particularly important, as it is the vector of virus causing bunchy top disease. It can be controlled by spraying rogar, Malathion and metasystox.
Nematode (Radopholus similis)
It is widely distributed in the banana growing areas. Affected plants do not respond to manuring and cultural operations. Before planting, suckers should be treated with Furadan granular nematicide. The nematicide is placed around the plants and is carried down into the soil by rain.