Effect of aqueous plant extracts on growth and development of tea mosquito bug, Helopeltis theivora Waterhouse

Experiments were carried out to study the effect of aqueous plant extracts of Azadirachta indica, Acorus calamus, Xanthium strumarium and Polygonum hydropiper on the development of tea mosquito bug, Helopeltis theivora Waterhouse. Significant effect on different developmental parameters of H. theivora was observed. The number of feeding spots produced by first instar nymphs was significantly reduced to 49. 83–109. 00 in plant extracts treated shoots as against 202. 33–205. 67 in untreated control. However in case of adults the same was reduced to 35. 17–76. 83 at 10-2% concentration. Fecundity of H. theivora was significantly reduced to 37. 50–55. 66 on the treated tea shoots with aqueous extracts of plants as against 107. 33–110. 17 in untreated shoots. The hatching percentage and adult longevity also decreased significantly. However the longevity of first instar nymph was lengthened (juvenile effect) to 2. 61-2. 97 days at 2–10% concentration.