Controlling the sucking insect pests in cotton with its ETL makes spraying economically affordable. Spray only if sucking pests (aphids + jassids + thrips + whitefly) appear on an average of five or more on a leaf. To find out ETL, select three leaves of 20 plants at random and count the sucking insect pests and divide it by 60 to calculate the average sucking pests per leaf.