Not a rose garden

While rainfall has declined, temperatures have risen - creating ideal conditions for pests such as looper caterpillar and tea mosquito to infest the light green tea shoots just before they are ready to be plucked for processing.

As a result the use of pesticides and fertilisers has nearly doubled in Assam's 800 big tea plantations, known as gardens, and the rising costs are making Indian tea less competitive.

Pressure on labour costs is part of the challenge for Assam’s tea industry. Producers agreed recently to increase tea workers’ daily wage to about $2, but local activists are calling for further increases as the labourers struggle to make ends meet.

The average temperature in Assam has risen by 1.4 degrees Celsius in the past century while rainfall is down by 200 mm a year, said R.M. Bhagat, chief scientist at the Tea Research Association in Assam's tea hub of Jorhat.

"In the last 30 years we have seen that the magnitude of the effect of climate change is pretty high," he said. "Rainfall has gone topsy-turvy. There is either too much or too little water, forcing planters to use sprinklers on what is a rain-fed crop."

Several tea garden labourers and planters said tea factories in Assam now only run for about six months. Lower rainfall led to a drop in tea exports last year, according to the Indian Tea Association.

"With rain so scarce, a day may come when Assam will not grow tea any more," said Subhash Chandra Barua, a tea scientist. "Planting a crop is fine but economic cultivation may not be feasible."

Some tea gardens have moved to cultivating black pepper, turmeric, ginger, vegetables and fruit alongside tea, while Indian scientists are testing tea varieties that can survive in hotter and drier conditions.