Economic injury level

Definition

The pest population density or damage threshold at which the cost of control measures equals the economic loss prevented by that control; the break-even point below which intervention is economically unjustified and above which control becomes profitable. EIL is calculated as (cost of control per unit area) ÷ (market value per unit of product × loss per pest unit × efficacy of control), yielding a dynamic threshold that varies with commodity prices, control costs, and management efficacy.

Etymology

From economic (Greek oikonomikos, household management) + injury (Latin injuria, wrong, damage) + level (Latin libra, balance, scale); coined in entomological literature during the development of economic thresholds and integrated pest management frameworks in the 1960s–1970s.

Example

In cotton production, the economic injury level for bollworm (Helicoverpa zea) might be 6 larvae per 100 plants when lint prices are high and insecticide costs are moderate, but that same EIL drops to 3 larvae per 100 plants when cotton prices fall or when cheaper biological control agents become available.

Synonyms

• EIL
• economic threshold (loosely, though technically distinct)

Related Terms

• economic threshold
• Integrated Pest Management
• Action threshold
• General equilibrium position
• Injury equivalent
• Damage function
• Pest density
• Scouting

Usage Notes

Distinguished from the economic threshold (ET) or action threshold, which is the pest density at which control measures should be initiated to prevent reaching the EIL; the ET is set below the EIL to account for control lag time and pest population growth. EIL is an absolute economic calculation, not a biological constant, and must be recalculated seasonally as market conditions, control technology, and crop value change. Some authors reserve 'economic injury level' strictly for the mathematical break-even point and use 'economic threshold' for the practical decision trigger, though usage varies regionally.