Forbidden fruit: Mystery fungus fells apples

Apple farmers of central Himachal Pradesh are a worried lot these days, confounded by a mysterious fungal disease that has no external manif...

Apple farmers of central Himachal Pradesh are a worried lot these days, confounded by a mysterious fungal disease that has no external manifestation but causes apples to rot and finally drop off trees. The core rot disease, first noticed last month, has already caused losses running into lakhs for the 400,000 apple farmers of the state.

The worst-affected are the orchards producing early apples of four popular varieties—Red Delicious, Rich-a-Red, Red June and Tydeman’s Early—all of which grow above 1,800 meters in the hill state. First spotted in Mandi, in the heart of the Karsog belt, the disease has now been reported in adjoining areas of Kullu and Shimla as well.

A team of scientists from the Y S Parmar Horticulture University, Solan, which surveyed the area recently, has ID’d the disease as mouldy core rot, triggered by facultative Alternaria or Trichothecium parasites that remain dormant on the plant surface till conditions of excessive moisture develop.

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The alarming factor for farmers is the complete absence of any external symptoms of the disease: The fungus attacks the seed cavity, ruining the fruit from the inside and finally causing it to drop off the tree. Early apples were to scheduled to have hit the markets in a few weeks; apples account for 75 per cent of Himachal’s total fruit production.

‘‘The disease can only be prevented by the use of certain sprays in the early flowering stage. After that, there’s no way to control it,’’ says Vijay Singh Thakur, senior plant pathologist at the Regional Horticulture Research Station, Mashobra.

‘‘But one can look on the disease as a natural culling process. The diseased fruits may drop off the tree, but the healthy ones continue to flourish.’’

Not all farmers are buying that line, claiming that the disease has affected 10-15 per cent of the crop even in the best-managed orchards. ‘‘At a time when a box of the early fruit varieties sells for Rs 1,000-1,100, mouldy core rot can leave one poorer by several lakhs,’’ says Ram Lal, who recently bought an 800-tree orchard in Karsog.

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Though some orchard-owners claim apples continue to drop off the trees, scientists who visited the area believe there is no cause for alarm for growers who followed the spray schedules at the pink bud and petal fall stages.

‘‘The disease is not new to the area and the infection is not more than five per cent,’’ claims Jagmohan Singh, V-C of the Parmar University.