Investigation of Scab Diaease of Mandarin in Kavre Distrisct and Chemical Control

Abstract

Present study was made on citrus scab disease of Citrus reticulata in Pipal Bot (Bakal) Kavre. Observation was made from December 2007 to December 2008. Infected fruits show somewhat circular, elevated spots. The lesions may be single or irregularly grouped. Severe infection of the disease produces premature fruit drop, severely external blemishes on fruit, reduce acceptability of the fruit in the fresh market, including deformation of leaf and defoliation of leaf. The causative agent of the disease was isolated from the diseased plant parts and pure culture was prepared. The conidial measurement was 7-10.75 X 2.75-5.25 µm. To confirm it, pathogenicity test was conducted on host plant and after the appearance of the typical citrus scab lesion on host, the fungus was re-isolated, thus proving the Koch’s postulates. The pathological and morphological characteristics confirm Elsinoe fawcetti as the causative agent of the citrus scab disease. Disease development was found to be proportionate to the time of fruit maturity and size of the fruit. The number of lesions increases with fruit size and maturity Two controlling chemicals, Carbendazim 50% w/p and Bordeaux mixture (1%) were sprayed on the plants in the citrus orchards in Pipal Bot Kavre. There was decrease in disease severity after a spraying of the chemical. The severity of the disease was calculated with reference to the plants that were not sprayed with chemical. It was observed that spraying of the chemical helped in deceasing the disease severity, Carbendazim 50% w/p was better in controlling the disease over the Bordeaux mixture. Integrated disease management is recommended in controlling disease rather than by spraying chemical fungicides only.