Study of the Disease Citrus Canker and Field Trial to Find its Effective Control Measure in “Kavre” Nepal

Abstract

Of all the agricultural pests and diseases that threaten citrus crops, citrus canker is oneof the most devastating. The disease,caused by the bacteriumXanthomonas campestrispv. citri,occurs in large areas of the world's citrus growing countries includingNepal.Severe infection of the disease produces a variety of effects including defoliation,dieback, severely blemished fruit, reduced fruit quality and premature fruit drop. The causative agent of the diseaseXanthomonas campestrispv.citriwas isolated fromthe diseased plants and pure culture was isolated. The isolated culture was subjected toGram staining, Catalase test, Oxidase test, O-F test, Starch hydrolysis, Nitrate reductiontest, Methyl-red test, Voges-prausker test, Indole production test, Urease test. To re-confirm it, pathogenicity test was conducted on host plant and after the appearance ofthe typical citrus canker lesion on host, the bacteria was re-isolated, thus proving theKoch’s postulates. Different controlling chemicals, Copperoxychloride (2.5%), Copperoxychloride +Kasugamycin (1000X), Bordeaux mixture 1% and 2% were sprayed to the plants incitrus orchard at Dhulikhel and the decrease in disease severity after spraying of thechemicals were calculated with reference to the plants that were not sprayed with thechemicals. It was observed that spraying of the chemicals helps in decreasing thedisease severity and Bordeaux mixture was superb in controlling the disease. Thechemical spray however was not able to eradicate the disease. It is concluded that Xanthomonas campestris pv. citri is the causative agent of thedisease Citrus canker and the spray of Bordeaux mixture very early with theappearance of first symptoms of the disease can eliminate the disease in citrus fruits tominimum level.