Yield Loss-infestation Relationship and Determination of Economic Injury Level of Tea Mosquito Bug

摘要

The nymphs and adults of tea mosquito bug, Helopeltls theivora Waterhouse (Hemiptera, Miridae), is a serious pest of tea in north-east India and causes extensive feeding punctures in the tender pluckable shoots due to which shoots dry up, become deformed and even curl up and yield of infested bushes is significantly reduced. Different levels of Helopeltis infestation were maintained by exposing the tea bushes to various periods of attack by Helopeltls theivora and foliar application of insecticides.Per cent shoot infestation and green leaf yield were recorded at weekly intervals. Regression analysis was used to determine the relationship between per cent shoot infestation and green leaf yield. The correlation between Helopeltis infestation and green leaf yield of tea was significantly negative. The economic injury level (E1L) of tea mosquito bug was found to be 3.75% shoot infestation based on the findings of field experiments conducted over the period of two years. The economic threshold level (ETL) was worked out at 2.81% shoot infestation.