Studies were carried out at Tocklai Tea Research Institute, Jorhat, Assam during 2011-2012 to assess the bioactivity of water, acetone and methanol extracts of Acorus calamus in terms of antifeedant, repellent, ovicidal, and field bioefficacy against Helopeltis theivora. The results were compared with a neem formulation, Neemazal-F 5% (Azadirachtin5%EC) and Thiamethoxam 25WG. Responses in terms of reduction of feeding spot, number of adult reached to the treated shoots, egg hatchability and reduction of shoot infestation in the field varied according to different solvent extract and concentration. All the extracts exhibited significant bioactivity compared to control. Among all the solvent extracts, acetone extract exhibited the highest bioactivity followed by methanol and water extracts. Effect was concentration dependent. The number of feeding spot was reduced significantly over control to the tune of 62-81% in acetone extract followed by 58-79% in methanol and 46-68% in water extract compared to 74% in Azadirachtin5%EC. All the extracts exhibited 25-52% reduction in egg hatchability and 88-100% repellency at the tested concentrations.
The most effective fraction i.e. acetone extract was further fractionated with silica gel column (60-120 mesh) chromatography by successively eluting with step-wise gradient of different solvents. Fraction III was found to be the most active fraction among those partitioned from the acetone extract and possessed 85.2% antifeedant activity at 0.5% concentration.
The acetone extract exhibited the highest reduction of shoot infestation (52-61%) under field condition followed by methanol (42-55%) and water extracts (30-51%) compared to 50-57% in Azadirachtin5%EC and 87-97% in Thiamethoxam 25WG. So the extract of Acorus calamus can be utilized effectively as one of the component of IPM for the management of tea mosquito bug in organic as well as conventional tea plantations.