Mass death of trees due to insects in evergreen forests prompts study

Officials and experts inspect boreholes in the heart of a dead Jala tree.

Jala or Jalari tree

The powder from the boreholes.

In a first-of-its-kind incident in the Western Ghats, more than 500 ‘Jala’ (Shorea talura) trees have died due to insect attack in the natural forests of Sirsi in Uttara Kannada district.

The tree, which entered the red list (vulnerable) of the International Union for Conservation of Nature (IUCN) in 2017, is seen in patches in the Western Ghats, especially in pockets of its evergreen forests. Due to its high timber value, the tree is ranked next to rose wood and has been overexploited.

However, the mass death of the trees in Belale, Golikoppa, Malenahalli, Hosalli and the surrounding villages of Sirsi taluk due to the attack of stem heartwood borer is seen as a strange phenomenon, with experts unable to pinpoint the exact reason. Farmers who noticed the trees drying up in quick succession had requested officials to visit the area.

Karnataka Biodiversity Board chief Anant Hegde Ashisar, who led a team of forest officials, entomologists and others, said that apart from the 500 trees which have already died, another 600 were drying up.

“Had it not been for the alert farmers of the village, we would not have known the extent of damage. I have recommended a detailed study to understand this phenomenon as well as for quick mitigation measures to save the trees,” he said.

S G Hegde, Deputy Conservator of Forest, Sirsi, said prima facie it looked like the heartwood borers attacked weak trees.

“We have not come across an attack of this magnitude in the ghats. Jala trees are already endangered. Some of those that died were over 200-years-old. We will consult experts to understand whether biotic disturbance in forests has added to the problem,” he said.

Conservation biologist Keshava H Korse said the death of trees was a symptom of a larger problem.

“Such mass deaths have taken place in plantations but not in natural forests which have a balancing mechanism that helps in containing the insects. The death of trees is a symptom of a larger problem of ecological imbalance and may also be linked to climate change. We urgently need an ecosystem management plan,” he said.

Entomologists Javare Gowda and Roopa Patil said the incident is similar to the sal heartwood borer attack in Madhya Pradesh where hundreds of sal trees have been killed. Roopa said a study was required to come up with a containment measure.

“We need to conduct a survey to ascertain the prevalence of the insect. The insect that attacked sal and the one killing trees in Sirsi are different. We don’t know how or when it has entered our forests,” Gowda said.