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20 pest species eating up leaves of mangroves in MMR identified

PUBLISHED ON DEC 29, 2019 11:35 PM IST

Scientists from the Institute of Wood Science and Technology (IWST), Bengaluru, have identified 20 species of pests responsible for mangrove trees losing leaves and drying up during and after monsoon months every year in the Mumbai Metropolitan Region (MMR). State mangrove cell officials said they will implement measures suggested by IWST scientists over the course of 2020 to protect mangroves.

HT had in August 2018 reported that after failing to determine why mangroves — which should ideally flourish during the monsoon months of August and September — were losing leaves and drying up every year, the state mangrove cell had appointed IWST for a first-of-its-kind study in India to identify pests affecting trees and suggest measures to control infestation.

IWST scientists carried out the study across mangrove forests in Airoli, Ghansoli and along the Thane-Vashi creeks between 2018 and 2019. The institute recently submitted its interim report to the state mangrove cell identifying six species of caterpillars, five species of grasshoppers, two species each of semi loopers, snails and weevils, and one each of leaf miner, skeletonizer and bag worm as defoliating pests which affect mangrove tree species such as grey mangrove (Avicennia marina), Indian mangrove (Avicennia officinalis), Apple mangrove (Sonneratia alba), cream coloured mangrove (Sonneratia apetala) and red mangrove or Asiatic mangrove (Rhizophora mucronata).

Report states that these pests, during their larval stage, feed mainly on the leaves and sometimes, the bark of mangrove trees. They eat away the leaves , consuming chlorophyll (a pigment essential for photosynthesis, the process plants use to make food), and lead to skeletonization or drying up of these trees. “While there is rapid regeneration during winter months, the annual reproductive cycle of these trees is affected, which may even harm humans or marine life,” said a scientist from IWST.

The preliminary report had found 14 defoliating pests, but the investigation revealed more details this year, said scientists. The interim report classified the defoliating pest species into severe, medium or negligible categories based on their intensity. “Among the 20 species, five fell in the severe category (mostly caterpillars, leaf miners and beetle species), seven in the medium category (grasshoppers, snails, weevils and bag worms) and the rest in the negligible category,” read the interim report.

While IWST was to submit its final report by March 2020, the state mangrove cell has extended the scope of the study. “We want to ensure that our mangrove trees are protected. For this, detailed suggestions shared by scientists will be implemented over the course of 2020,” said Virendra Tiwari, additional principal chief conservator of forest (mangrove cell).

N Mohan Karnat, additional principal chief conservator of forests (protection), Maharashtra forest department, said there was a possibility that these pests may have some impact on fishermen and marine life in the same region. “We need to understand the overall impact as some maybe beneficial, while the others may be harmful. We have been told to not implement chemical-based solutions to get rid of the pests as they may cause more harm, and instead focus on organic solutions to ensure trees remain protected,” Karnat said.

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