Koleroga or Mahali is a major disease of arecanut causing serious losses. The pathogen is a fungus Phytophthora palmivora. Spraying the. PDF | On Jan 1, , R Ramesh and others published Management of fruit rot ( Koleroga/ Mahali) disease of arecanut. Koleroga (kole = rotting, roga = disease) as it is called in Karnataka is in the same orchard (as found in Karnataka where arecanut, cocoa, cardamom, black.
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TNAU Agritech Portal :: Crop Protection
This disease was first reported in India in and has been serious on areca palms Areca catechu; supari in the western peninsular parts of our country. It has loleroga been arexanut from Assam.
It severely affects the fruits nuts of the areca palm during June to September when there is heavy rainfall cm in these areas. The areca fruits surfaces get rotten as a result of the disease.
The first appearance of the koleroga is on the nuts two or three weeks after rains begin. Water soaked areas usually manifest towards the base of the nuts. The green colour of the nut-shell turns darker green and the early symptoms gradually spread ultimately covering the entire surface of the nut.
Attacked nuts soon begin arecannut fall off from bunches. This is the most conspicuous and dangerous stage and is a sure sign of the disease in the plantation. Felty whitish mass of fungal mycelia soon cover the entire surface of the fallen nuts. Although the disease is predominant on the nuts, it occasionally attacks the crown of the palm resulting in rotting and drying.
The leaves and bunches wither away soon. The disease spreads from palm to palm and from orchard to orchard. The hyphae invade inter- or intracellularly and produce sparsely distributed finger-shaped, occasionally branched haustoria in the host cells. The sporangiophores are irregularly branched and are about 2.
They are deciduous, pedicellate, and papillate. Each sporangium gives rise to zoospores after a few kolerogs of their formation.
Zoospores emerge out of the sporangia in the presence of abundant light and atmospheric humidity. Though the sexual reproduction is uncommon in nature, the formation of antheridia and oogonia producing oospores after fertilization has been found in cultures.
The antheridia are diclinous and amphigynous. The pathogen is considered to perennate in the infected tree tops during entire dry season ranging from January to June because of two reasons: The chamydospores formed in the infected fallen nuts on the soil serve as the perennating structures of the pathogen. It is believed that where many crops are grown simultaneously in the same orchard as found in Karnataka where arecanut, cocoa, cardamom, black pepper, and citrus are grown simultaneously in the same plantationand they are infected by two to three species of the some pathogen e.
The source of primary inoculum, are the sporangia produced by the perennating pathogen structures, the chlamydospores formed in the infected fallen nuts, and, probably, the zoospores produced by the perennating oospores. During the onset of the rainy season, these structures are carried to young nuts by various agencies and germinate there upon causing primary infection. Sporangia produced from primary infection lesions serve as the source of secondary infections during the growing season.
Heavy rainfall and constant moist conditions of the atmosphere are the chief predisposing factors for the disease. Therefore, intermittent rains maintaining constant humidity in the atmosphere with alternating sunshine abundant light are more conducive for the rapid spread of Koleroga.
Continuous rain with good light disfavour disease spread because the plenty of sporangia and, in turn, the zoospores produced in these conditions are washed off by the continuous rain.
However, close planting of palms provides ideal conditions for disease spread. Cleanliness and sanitary cultural practices, particularly the destruction of diseased tops of the palms and other plant parts, are of foremost importance in disease management.
Koleroga Disease of Areca Palms: Symptoms and Management | Plant Pathology
Although the height of palms and the situation of affected parts of the top make spraying difficult, the latter is found to be very effective. Copper fungicides such as 0. One spray of Bordeaux mixture in the month of May as prophylactic measure and another after 6 weeks during break in the monsoon prove quite effective in controlling disease.
Saraswathy and Nambiar stated that the systemic fungicides such as Aliette and Ridomil at 0.
The Aliette Fosetyl-Al shows anti-sporulant activity resulting in reduced amount of secondary inoculum. Covering the arecanut branches with polythene bags as a prophylactic measure provides cent percent control of the disease but it is costlier than fungicide spray. Email will not be published required. Please enter an answer in digits: Upload Your Knowledge on Botany: Brown Spot Disease of Maize: Symptoms and Management Plant Pathology.
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