Tea growers in India's north-eastern Assam state have warned that pests could cut output by between 10 and 15% this year.
The tea industry is one of the main employers in Assam
The culprit is the Helopeltis bug, also known as mosquito tea bug, which has attacked more than 25% of Assam's plantations.
The outbreak has been blamed on cash shortages which have made pest control measures impossible.
Assam is India's biggest tea-growing region, accounting for 55% of the country's annual crop.
The Helopeltis infestation comes at a time when India's $1.5bn tea industry has been hit hard by overproduction and stiff competition from Sri Lanka and Kenya.
The country's tea exports fell to 190 million kilograms in 2003, down from 220 million the previous year.
Weekly auction prices have fallen by more than a third, slashing farmers' revenues.
"Many tea plantations are now unable to carry out the regular maintenance and pest control measures. They are suffering a severe money crunch," said Dhiraj Kakoty of the Indian Tea Association.
Helopeltis typically attacks tea plants during the winter months.
Tea growers now fear that their plantations will be vulnerable to fresh pest infestations when the weather warms up.
"We are not really apprehensive about red spiders, as the mites generally attack weak plantations in April and May," one tea planter told the Agence France Press news agency.