Consider a cup of tea: too much water and it's barely delectable; not enough and no amount of sugar can mask the bitterness. Sylhet's tea gardens are in a similar conundrum this year, thanks to erratic rainfall. Deluge has followed dry spell. Tea growers have had to manage sapling growth through periods of water scarcity, and then deal with spider and insect infestations arising from overly wet conditions. It's not good news for the industry, which may experience a production shortfall this year.

“Either too little or too much rain will stifle tea leaf growth,” says Shahjahan Akondo, tea leaf researcher and the general manager of New Samanbagh tea estate. “Heavy rain damages and clogs the soil, making it more difficult for tea plants to effectively tap into water reserves, especially in flat areas. As a result the leaves become brittle and crop quality is reduced.”

Rain also creates ideal conditions for infestations of red spiders and helopeltis, the insect pest that is commonly known as the tea mosquito or mosquito bugs. Both spiders and tea mosquitoes damage tea leaves.

“High rainfall has left gardens vulnerable to pest infestation,” observes Md Nurul Mohmain Milton, general secretary of the environmentalist journalist forum. He believes the erratic rainfall pattern is a symptom of climate change.

Harunur Rashid, senior adviser at the Srimangal Meterological Centre confirmed to The Daily Star that rainfall from April to June has been double this year, compared to the last three years. “In the three-month period this year the area received around 1,921 millimetres of rain. It is usually closer to half that amount,” he says.

Yet the region's tea gardens have also suffered from dry spells, a problem exacerbated by a shortage of shade trees needed to protect the crop during sunny, dry conditions. “Some wood smugglers are cutting shade trees, taking advantage of lax security in the gardens,” observes Shahjahan Akondo.

Milton meanwhile suggests river and canal excavation is crucial, to bring more water into the tea gardens, where at times there have been insufficient reserves to allow for much needed irrigation. He also notes the problem of too few shade trees. “Each acre should be covered by more than 65% in shade trees,” he says. “Now the average is less than 20%. It's a factor that really hits production.”

At the time of interview, director of the Bangladesh Tea Board, Dr Mohammad Ali, was also lamenting a lack of rain. “If there is no rainfall in the next few days it will cause colossal harm,” he says. “Under the scorching heat new tea saplings are dying. Good rainfall is crucial for their growth.” He notes that efficient irrigation to compensate is difficult due to the low water levels in rivers. “On the other hand, if the rainfall is too heavy it is also problematic,” he adds.

Central president of the Bangladesh Tea Labour Union, Makhon Lal Karmakar, has echoed the concerns of others about production this year. “Most tea workers cannot achieve their targets due to sick tea leaves,” he says. “Global warming is largely responsible.”

Dr Mohammad Ali states that last year the industry produced 85.05 million kilograms of tea leaves. The target for this year is 110 million kilograms. “Due to adverse climate conditions it will be hard to achieve this year's target,” he says.

Any shortfall is likely hit tea exports the hardest. With domestic demand for tea on the rise, less Bangladeshi tea is available for sale abroad.