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Agronomy QUESTION #2047
Question 1
The Economic Threshold Level (ETL) in crop pest management is defined as:
  • The pest density at which the crop begins to show visible damage symptoms
  • The pest population density at which control measures must be initiated to prevent the pest from reaching the Economic Injury Level (EIL) — accounting for the time needed for control measures to take effect✔️
  • The maximum pest density a crop can tolerate without any yield loss
  • The point at which 50% of the crop stand is destroyed by the pest
Correct Answer Explanation
ETL (action threshold) is always set BELOW the Economic Injury Level (EIL) — the pest density at which economic damage equals cost of control. The ETL triggers action while the pest population is still rising, allowing time for control measures to prevent the EIL from being reached. ETL < EIL is a fundamental IPM concept.