Resistance to insecticides in field-collected populations of tea mosquito bug (Helopeltis theivora Waterhouse) from the Dooars (North Bengal, India) tea cultivations

Abstract

Dose ($LC_{50}$) and time-mortality response ($LC_{50}$) parameters are used to compare resistance levels of field-collected populations of the tea mosquito bug, Helopeltis theivora (Waterhouse) from Kalchini tea plantations of the Dooars, North Bengal, India with the reference strain collected from Darjeeling foothills against eleven insecticides by following leaf-dip technique. Tea plantation of Darjeeling is largely organic, that had never used synthetic pesticides in its history, whereas Kalchini plantation is conventional that routinely uses synthetic pesticides. The field-collected Kalchini strain of H. theivora showed a high Resistance Ratio level (> 10 folds) both in ($LC_{50}$) (20.00 - 17564.11 folds) and ($LC_{50}$) (20.20 - 45.99 folds) parameters for the tested insecticides. This is the first report on the reduced susceptibility of H. theivora populations to eleven insecticides (one organochlorine, three organophosphorus, two neonicotinoids and five synthetic pyrethroids) from Kalchini tea cultivations in the Northeastern Dooars region of India.