At a time when apple harvesting is in the full swing, outbreak of fungal disease 'Marssonina coronaria', which causes premature defoliation, is threatening orchards in the major apple-growing areas of the state.
The rapidly spreading disease triggered by fungus 'Diplocarpon mali' is leading to panic among fruit growers as 80% of apple crop is still to be harvested.
During the premature leaf fall in the apple crop, initially leaves develop dark-green spots on the upper surface, which later turn brown. The infected leaves then turn yellow and fall in the mid-season.
Vikas Negi, an orchardist from Koku Nullah village in Kotkhai said in some areas of Kotkhai and Jubbal the premature leaf fall has surfaced recently. “It has been witnessed in some areas of Sharontha, Padshaal, Halaila of Jubbal and Kotkhai, where growers are taking necessary steps to control the disease,” he said.
Kush Bhardwaj, a young orchardist from Jubbal, said the apple season has started, but fungal attack has caused early leaf fall that was affecting the crop adversely in some areas.“Premature leaf fall is a fungal disease (Marssonina coronaria) and humid climate is favourable for it,” said deputy director, horticulture department, and plant protection scientist Ishwar Das Gupta.
Elaborating, he said the problem of premature leaf fall has not attained alarming proportions and it can still be controlled by spraying fungicides. He added that reports being received at the horticulture department reveal that till far only 5-6% apple crop has been affected due to premature defoliation.
In Shimla district, Jubbal and Kotkhai, Rohru and Chirgaon; in Kullu district, Parbati valley and Lag valley; in Mandi district, the Janjehli area and Pangi area of Chamba district are partially affected by this fungal disease, said Gupta.
Underlining the need of proper weed management in apple orchards, he said bushes and grass under the apple tree usually trigger the problem of premature leaf fall as the undergrowth causes dampness around the tree.
Further, he added that rootstocks M-2, M-4, M-113 and M-114 were resistant to premature leaf fall.
Malady and remedy
Premature leaf fall of apple first appeared in the epidemic form in Shimla and Kullu districts of the state in 1995.
This is a fungal disease 'Marssonina coronaria', which is caused by 'Diplocarpon mali'.
Plant protection scientist ID Gupta said the spray should be given form May onward when apple is of pea-size, with a gap of three weeks till the harvesting of the crop.
Collect and burn the leaf litter from the orchard floor in the winter as the causative fungus survives in the infected fallen leaves.
Prune apple trees in winter to allow sunlight in the tree canopy, which will check excessive humidity.
Name Quantity/200litre of water
Carbandazim/Thiophenate Methyl 100gm