A total of 56 trees along the ‘girivalam’ path have withered mainly due to pest attack and drilling of nails, Collector K.S. Kandasamy said.
Days after a few environment activists and residents alleged that there was a bid to destroy trees along the ‘girivalam’ path using chemicals, the district administration ordered soil testing and inspection by officials of the Forest Department and faculty of Tamil Nadu Agricultural University’s Agricultural College and Research Institute, Vazhavachanur.
“There are a total of 1,185 trees along the ‘girivalam’ path. During a survey, we found that 62 trees have withered. Six of these trees could be saved, and we have started intervention efforts. The allegation that these trees withered due to acid is not true. We had taken soil samples from all 62 trees and tested. No use of acid or chemical was found,” Mr. Kandasamy said.
Drilling of nails
Pest attack was one of the main causes, he said, adding, this was intensified by drilling of nails on the trees – something that should be prevented hereafter. “These trees have withered over a period of two years. If noticed earlier, we could have retrieved these trees. I have asked the officials of the Highways Department to go around and watch the trees every month end. If any of the trees are found to be unhealthy, the agricultural institute will be roped in to take necessary measures,” he said. He said massive tree plantation would be taken up soon.
The Collector, along with faculty members of the agricultural college, conducted an inspection on Thursday.
V. Radhakrishnan, assistant professor, Entomology, Agricultural College and Research Institute, Vazhavachanur, said of the 62 trees, six could be retrieved. “The remaining are 100% dead and should be uprooted. Some of them included ‘konnai’ and tamarind trees.
Stem borer attack
“The main cause is stem borer attack. The pest lays eggs one metre from the ground level. For 10 months, it will be in the grub stage during which it will enter the tree through small holes. One adult can lay 90 to 100 eggs, and one can imagine what will happen to a tree if all 100 emerge. It will kill the tree,” he explained.
The grub eats the soft tissues of the tree that results in the lack of absorption of nutrients, he said, adding, “After 10 months, it reaches the pupa stage. In two months, it will become an adult – stem borer.”
Taking a closer look at the withered trees, the faculty members found at least 50 to 150 holes on the trees. “As a result of this pest attack, a brownish colour was seen around the holes. The trees also suffered secondary infections. There was growth of ‘ganoderma lucidum,’ a kind of mushroom, on the trees, and also termites,” he added.
He said the trees that were more than four to five years old had become susceptible to pest attack. This, coupled with drought, did the damage. Once the dead trees were uprooted, re-planting could not be done at the same place unless the soil was treated, he said.
“The trees died due to pest and disease attack. Once the pest attacks, the resistance of the tree reduces, and disease occurs. Already, there are drought conditions here, as Tiruvannamalai has had no rain for the last five years,” M. Sivaprakash, assistant professor, Forestry, Agricultural College and Research Institute, Vazhavachanur, noted.
When the stem borer attacked a tree, it punctured the tissues that help in absorption of water and nutrients, he said, adding that while “ganoderma lucidum” was a wood-decaying fungus, the termites fed on cellulose. “In dead trees, the barks start to peel off. This is what happened to these trees along ‘girivalam’ path. We also found 50 to 60 nails on the trees to fix banners. This damaged the tissues,” he observed.
Mr. Radhakrishnan said they had tried to retrieve one of the six trees on Thursday. “We can follow certain treatment methods. Swabbing of tree trunk using kerosene and coal tar in 1:2 ratio can be done to prevent further laying of eggs. This will also prevent termite attack,” he said.
“The holes on the trees can be closed using clay. A piece of cotton dabbed in insecticide can be inserted into a hole and closed using clay. In addition, we have suggested use of nutrients and manure for the trees too,” he further said. They pointed out that it should be ensured that no nails were drilled into the trees.
