Principles of Integrated Pest Management (PIDM)

1. Lecture 6
Calculation and dynamics of economic
injury level and importance of Economic
threshold level
RK Panse
Subject: Principles of Integrated pest and Disease Management

2. Economic Injury Level (EIL)
 Economic Injury Level - pest density that will justify
the cost of applying control measures
 EIL is the “break-even point” – the pest density at which the
cost of control equals the amount of damage caused by that
pest
Pest density is:
 Above the EIL - damage exceeds the cost to control
 Below the EIL - damage is lower than the cost to control
**Best to control NOW!
$ $
=

3. Economic Injury Level
EIL 
C x N
V I
C = cost of controlling the pest per unit area (eg. Rs/acre)
N = number of pests injuring the commodity per unit area (eg. #/acre)
V = value of the commodity per unit area (eg. Rs/acre)
I = percentage of commodity injured (% loss expressed as a decimal)
• EIL is expressed as number of pests per unit area (pest density)

4. EIL Equation
VIDK
C
EIL  P
C = Cost of management/area (eg. $/ha)
V = Market value/ unit of product (eg. $/Kg)
I = Injury/(insect/area) (eg. chewed leaves/insect/ha*)
D = Damage/area/injured unit (eg. (Kg lost/ha)/chewed leaf*)
K = 1-proportion of unavoidable injury
EIL is expressed as number of pests per unit area (pest density)
*I x D is often combined into D’ which is weight lost per insect

5. EIL Example
 Cost of controlling a pest/acre is Rs 500 with
800 insects causing injury on the commodity. This
commodity is valued at Rs 2000/acre and the
percentage commodity injured by the pest is 10%.
Calculate the EIL for this pest.
 Main driving forces for the EIL is the cost of control
and the value of the commodity
500800

400000
 2000
VI 20000.10 200
EIL 
C  N

insects / acre

6. Economic Threshold (ET)
Number
of
insects
Time
 Remember ….EIL is the lowest level of pest that will cause
economic damage
 Control actions take time to show their effects!!
 Economic (Action) Threshold (ET) – the pest level at which
control measures should be taken in order to avoid losses
Management activity
EIL
ET

7. Economic Threshold
 What factors are important when determining ET?
 Lifecycle of your pest
 Time required for your control action to take effect
 Environmental conditions
 ET is not calculated but will always be below the EIL

8.  Main factors include:
 market value (V) - inverse relationship with EIL: as
market value increases, less injury is tolerated
 management costs (C) – linear relationship: as the
cost increases, net benefits decreases
 injury per insect (I) – inverse relationship
 Insect numbers (N) – linear relationship with EIL
Dynamics of Economic Injury Levels
V I
EIL 
C x N

9. Importance of ETL
1. Amount of physical damage related to various pest densities.
2. Monetary value & production costs of the crop at various levels of damage
3. Monetary loss associated with various levels of physical damage
4. Amount of physical damage that can be prevented by the control measure
5. Monetary value of the portion the crop that can be saved by the control measure
6. Monetary cost of the control measure
7. History of the field
8. Determining the danger of the pest at different stages of the crops development
9. The pest distribution
10. How much aesthetic or economic damage can be tolerated
11. Establish a treatment level that keeps the pest population small enough.
12. Ultimate destination of the crop, what the standard of the end consumer is.
13. Ability to control the pest rapidly and effectively
Importance of Thresholds
1. The main importance is for decision making on scheduling of control methods
2. To establish the optimal amount of control which can be used to minimize risk of
economic damage and environmental hazards