A lethal fungus infection is killing Anjili (Artocarpus hirsutus) trees in Southern Kerala.

Plant specialists from the Kerala Forest Research Institute, Thrissur, have identified the pathogen as Ganoderma sp. The spread of disease was recently reported in Anjili trees on the Indian Space Research Organisation campus at Valiyamala and the plantations at Pachamala, Bharathannur and Chekkonam forest stations under Palode forest range.

Once infected, the trees gradually dry up. The decay sets in at the wood collar, the base part of the wood, which comes into contact with the soil. Anjili is one of the widely found homestead trees of Kerala. The species is also endemic to Western Ghats. This is also one of the indigenous trees which are farmed for its hardwood.

“The pathogen causes heart rot and root decay and takes a long time to cause tree mortality and hence the infection would have happened a few years before. The heavy monsoon showers the State received during the present season might have provided a favourable condition for the increased activity of the pathogen and sudden incidence of tree mortality,” said T.V. Sajeev, a scientist at the Institute. The infection, it is feared, would leave a significant economic impact as the timber is widely used for making furniture and construction of boats and body of lorries. The presence of fibre in the wood, which reduces its brittleness, makes it a preferred species for such uses.

“The close spacing of the trees in the plantation would have facilitated the spread of the pathogen which happens through soil, water and air. Spores of the pathogen will also remain in the soil keeping live the possibility of spread of disease,” said P. Sujanapal, another scientist who inspected the trees at the plantations.

The team that inspected the infected trees included T.K. Hrideek and Mallikarjuna Swamy.

“As the infection leads to the degeneration of the wood, the trees will have to be cut down and converted into timber. Once cut, the infected trees would still decay if left at the humid sites. Hence, it is important to season the timber early enough,” said Dr. Sajeev.

Many homesteads consider the species as a capital asset tree, which is harvested to meet a big economic demand. It is also considered as an upper stratum tree as the mature tree would grow up to a height of 30 metre.

The slow-growing species would take around 50 years to mature. The timber of a fully grown tree would have an average girth (diameter of the wood at chest level) of 2 metre, researchers said. The plant specialists have suggested treating the stump of the tree, which remains in the soil, with Bordeaux mixture. An area of one meter space around the stump should be sprayed with 0.4 per cent Copper oxychloride at the rate of 15 litres per tree.

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