Hard rot disease, a fungal infection of plants characterised by lesions with hard surfaces and rotten tissue, is affecting an increasing number of pasur (Xyicarpus mekongensis pirre) trees in different parts of Sundarban, the largest mangrove forest in the world, researchers and experts said.
Forest department officials, however, described it as just a natural process as old trees, which had not been felled for 30 years, decayed and claimed that the infection would not harm the natural regeneration power of the species in the forest.
Sundarban, with an area of 6,017 square kilometre located in the country’s south-west in the lap of the Bay of Bengal has 334 species of plants.
pasur trees, which cover nearly 1 per cent of the forest, are an important species of the forest because of their great environmental and economic value.
The disease affects pasur largely in the north-western part of the forest where the salinity level and presence of iron, calcium and magnesium in the soil are higher than other areas of the forest, said ASM Helal Siddiqui, a Khulna-based researcher in the Mangrove Silviculture Division, which is part of the Bangladesh Forest Research Institute.
He referred to a 2010 study of the division which found that 64 per cent of pasur trees in the Kalabogi area and 62 per cent of the trees in Bojboja were infected with the disease.
It also found 60 per cent of the pasur trees in Baniakhali, 54 per cent of the trees in Kashiabad and 48 per cent of the trees in the Chunkuri area were infected.
In the Supoti area in the eastern part of the forest, where there is far less salinity (0 part per thousand to 5PPT), only 17 per cent of the pasur trees are infected, he said.
Helal, who has been working on Sundarban issues since 1993, said that earlier they used to see the disease in old trees but nowadays they found the disease in young trees.
He said that the infection is largely found in Baniakhali and Kalabogi areas of the forest where they found high levels of mangnesium, iron and calcium and the water salinity ranges between 20PPT and 30PPT in the areas, he said.
He also suspected that other environmental causes may help explain the infection.
The Mangrove Silviculture Division researcher told New Age that he was concerned that unless the infected trees were removed them from the forest, their presence could result in great harm.
Khulna University’s forestry and wood technology teacher Mahmood Hossain told New Age that hard rot disease had been found in pasur trees in the forest previously but the number has increased in recent years.
Khulna circle conservator of forest Akbor Hossain told New Age that although the forest department has not undertaken any research on the disease, he did not think its presence in old trees would cause any problem.
‘The forest department has no research on hard rot disease of any tree in Sundarban and has no information about presence of the disease in the forest.’
He explained that the felling of the trees in the forest had been stopped for more than 30 years and that the presence of the disease in the trees was part of their ordinary lifecycle.
The Khulna circle forest conservator also claimed that the decay would not harm the natural regeneration power of the species in Sundarban.
-With New Age input
