Feb. 15: Eco Park, Calcutta's favourite weekend hangout, has a small but deadly foe - mosquitoes.

Swarms of mosquitoes descend on the 480-acre park as dusk sets in, forcing visitors to beat a hasty retreat.

Evenings, the best time to visit the park, see the crowd swelling as many throng the banks of the 100-acre water body.

A constable posted at the outpost inside the park said mosquitoes make it difficult to stand or sit in one place in the evening.

"Mosquito coils are of no help. They are everywhere... there's no escaping the sting," he said.

The park sees a steady stream of visitors during winter and this New Year's Day it recorded a footfall of 200,000.

The gates open at noon and close at 7.30pm from Tuesdays to Saturdays. On Sundays and holidays, the gates open an hour earlier at 11am. The park is closed on Monday. Entry tickets can be bought till 6.30pm.

But those entering the park in the evening are seen making a beeline for the exit way ahead of the closing time, thanks to the mosquitoes.

"Last week, my wife and I went to the park in the evening. Soon after we entered, there was the drone of mosquitoes everywhere... it was unbearable. We rushed out as fast as we could," Rahul Chowdhury of New Town said.

A Hidco official accepted the mosquito menace but said the insects could not breed in the water body since boats, including motorised ones, keep plying throughout the day.

"Mosquitoes breed in stagnant water. The propellers of boats would make it impossible for them to breed here. We even had the water checked by a vector biologist and no larva was found," he said.

The park has two canals close by and mosquitoes breed there as the water is mostly stagnant, the official said.

Hidco had sought the help of a biologist who advised them to spray citronella oil and BTI (bacillus thuringiensis israelensis) on the canal waters to keep a check on the mosquito population. He had also suggested that the canals be cleaned.

It is clear that the authorities have failed. Even morning walkers and cyclists are giving the park a miss because of the mosquito menace.

Cyclists who were part of an event at the park last Sunday said they could barely stand in one place. "Mosquito bites early in the morning were frustrating to say the least," one of the participants said.

Hidco chairman Debashis Sen said he was aware of the problem. Steps have been taken to keep mosquitoes at bay, he said.

"We are fogging the area regularly and spraying larvicide. But we are still receiving complaints."

The mosquito population sees a jump when winter departs and summer sets in, Bhaskar Narayan Chowdhury, a virologist and microbiolgist, said.