06-08-2013, 04:50 PM
Prevalence and Management of Smoky Canker of Apple through Fungicidal Paints
ABSTRACT
The incidence of various cankers diseases on apple (Malus domestica Borkh.) in Kashmir valley has increased manifold in the recent years, causing huge economic losses through girdling of limbs and branches, blightening and die-back of twigs , ultimately leading to the death of either whole or part of the tree. Survey of the apple orchards revealed the prevalence of five different types of canker diseases - Smoky canker, Stem bark canker, Valsa canker, Anthracnose canker and Phomopsis canker - with varying degrees of incidence and intensities. Smoky canker (Diplodia seriata), the most prevalent canker was characterized by the appearance of sunken reddish brown lesion which on enlargement became elliptical, developed series of concentric rings, turned smoky, girdled the affected limb or branch and roughened the large tree trunks. Leaf spots typically characterized by the appearance of frog-eye lesion and fruit rot commonly known as black rot was characterized by the appearance of concentric rings, studded with black pycnidia indicating the prevalence of all the three phases of the disease. Stem bark canker (Botryosphaeria dothidea) appeared as sunken reddish brown lesion, occasionally with purplish margin, which on enlargement became elliptical, developed vertical and horizontal fissures, turned black and brittle and completely girdled the affected tree part. Fruit rot commonly known as white rot appeared as small, sunken light green spot surrounded by light brown area, which on subsequent enlargement turned light brown, became depressed and developed series of concentric rings. Valsa canker (Valsa ambiens) mostly originating as vertical crack along the branch/twig axis developed into pale yellowish water- soaked area, which later turned brownish and brittle and caused collapse of the branch by down-ward elongation and depression. The anthracnose canker (Cryptosporiopsis sp.) appeared as small water soaked area which extended along the branch/twig axis, rendered the diseased bark brownish, and on rupturing finally peeled-off. The Phomopsis canker on the other hand (Phomopsis mali) observed only on twigs manifested as small brownish lesion, extended up-and down- ward, became sunken, turned dark brown and pappery and caused death of twig through girdling. The management of the most predominant canker disease “Smoky Canker” (Diplodia seriata De Not.) through application of six different linseed oil –based fungicidal paints four times a year at intervals of three months separately on existing scrapped and unscrapped cankers revealed that the application of the fungicidal paints on scrapped cankers completely checked the further spread of the cankers and exhibited wound healing without recurrence of the diease.Carbendazim in combination with either chlorothalonil or captan gave 92.00 and 84.00 per cent wound healing followed by admixture of Carbendazim with either copper- oxychloride (80.00%) or mancozeb (76.00%) . Bordeaux and Chaubattia proved least effective in wound healing. Application of the fungicidal paints on unscrapped cankers however, failed to restrict canker elongation.