📈 Pest Monitoring, Surveillance, and Forecasting

Pest monitoring in IPM tracks phytophagous insects and their natural enemies to support timely, evidence-based crop protection decisions. It focuses on changes in insect distribution and abundance, life-history information, and the influence of biotic and abiotic factors on pest populations.

Monitoring provides

• Information about insects and their life history
• Influence of biotic and abiotic factors on pest population

Pest Surveillance

Refers to the constant watch on the population dynamics of pests, its incidence and damage on each crop at fixed intervals to forewarn the farmers to take up timely crop protection measures.

Three basic components of pest surveillance

Determination of

a. the level of incidence of the pest species b. the loss caused by the incidence c. the economic benefits the control will provide

Pest Forecasting

Forecasting of pest incidence or outbreak based on information obtained from pest surveillance.

Uses

• Predicting pest outbreak which needs control measure

• Suitable stage at which control measure gives maximum protection

Two types of pest forecasting

a. Short term forecasting - Based on 1 or 2 seasons b. Long term forecasting - Based on affect of weather parameters on pest

Objectives of Pest Surveillance

• To know existing and new pest species
• To assess pest population and damage at different growth stage of crop
• To study the influence of weather parameters on pest
• To study changing pest status (minor to major)
• To assess natural enemies and their influence on pests
• To study effect of new cropping pattern and varieties on pest

Survey

Conducted to study the abundance of a pest species

Two types of survey - Roving survey and fixed plot survey

Roving survey

• Assessment of pest population/damage from randomly selected spots representing larger area

• Large area surveyed in short period

• Provides information on pest level over large area

Fixed plot survey

Assessment of pest population/damage from a fixed plot selected in a field. The data on pest population/damage recorded periodic from sowing till harvest. e.g. 1 sq.m. plots randomly selected from 5 spots in one acre of crop area in case of rice. From each plot 10 plant selected at random. Total tillers and tillers affected by stem borer in these 10 plants counted. Total leaves and number affected by leaf folder observed. Damage expressed as per cent damaged tillers or leaves. Population of BPH from all tillers in 10 plants observed and expressed as number/tiller.

Qualitative survey - Useful for detection of pest Quantitative survey - Useful for enumeration of pest

Sampling Techniques

Absolute sampling - To count all the pests occurring in a plot Relative sampling - To measure pest in terms of some values which can be compared

over time and space e.g. Light trap catch, Pheromone trap

Methods of sampling

a. In situ counts - Visual observation on number of insects on plant canopy

(either entire plot or randomly selected plot) b. Knock down - Collecting insects from an area by removing from crop and

(Sudden trap) counting (Jarring) c. Netting - Use of sweep net for hoppers, odonates, grasshopper d. Norcotised collection - Quick moving insects anaesthesised and counter e. Trapping - Light trap - Phototropic insects Pheromone trap - Species specific Sticky trap - Sucking insects Bait trap - Sorghum shootfly - Fishmeal trap Emergence trap - For soil insects

f. Crop samples

Plant parts removed and pest counted e.g. Bollworms

Stage of Sampling

• Usually most injurious stage counted

• Sometimes egg masses counted - Practical considerations

• Hoppers - Nymphs and adult counted

Sample Size

• Differs with nature of pest and crop

• Parger sample size gives accurate results

Decision Making

• Population or damage assessed from the crop

• Compared with ETL and EIL

• When pest level crosses ETL, control measure has to be taken to prevent pest from

reducing EIL.

Economic Injury Level

• Defined as the lowest population density that will cause economic damage

(Stern et al ., 1959)

• Also defined as a critical density where the loss caused by the pest equals the cost of

control measure

EIL can be calculated using following formula

EIL = [ C ] V x I x D x K

(or) [ C ] VIDK

where,

EIL = Economic injury level in insects/production (or) insects/ha C = Cost of management activity per unit of production (Rs./ha) V = Market value per unit of yield or product (Rs./tonne) I = Crop injury per insect (Per cent defoliation/insect) D = Damage or yield loss per unit of injury (Tonne loss/% defoliation) K = Proportionate reduction in injury from pesticide use

Worked examples of EIL Calculate EIL in terms of pest population/ha with following figures C = Management cost per unit area = Rs.3,000/- per ha V = Market value in Rs./unit product = Rs.1,000/tonne

I = Crop injury/pest density = 1% defoliation/100 insects D = Loss caused by unit injury = 0.05 tonne loss/1% defoliation K = Proportionate reduction in

injury by pesticide application = 0.8 (80% control) C 3000 EIL = = VIDK 1000 x 0.01 x 0.05 x 0.8

EIL = 7500 insects/ha

Economic threshold level (ETL) or Action threshold

• ETL is defined as the pest density at which control measures should be applied to

prevent an increasing pest population from reaching Economic Injury Level (EIL)

• ETL represents pest density lower than EIL to allow time for initiation of

control measure

Factors Influencing ETL and EIL

a. Market value of crop b. Management costs

Primary factors

Secondary factors

c. d.

Degree of injury per insect Crop susceptibility to injury

a. Market value of crop

When crop value increases, EIL decreases and vice-versa b. Management of injury per insect

When management costs increase, EIL also increases c. Degree of injury per insect

- Insects damaging leaves or reproductive parts have different EIL (Lower EIL for

Rep. part damages)

- If insects are vectors of disease EIL is very low even 1 or 2 insects if found management to be taken

- If insects found on fruits - Marketability reduced - EIL very low e.

Crop susceptibility to injury

- If crop can tolerate the injury and give good yield. EIL can be fixed at a higher

value

- When crop is older, it can withstand high pest population - EIL can be high

Tertiary factors Weather, soil factors, biotic factors and human social environment These tertiary factors cause change in secondary factors thereby affect the ETL and EIL.

lastmod: 2026-05-24T00:00:00+05:30

Summary Cheat Sheet

• Pest monitoring measures pest incidence, damage, and field trends on a regular basis.

• Surveillance and forecasting help predict likely outbreaks before economic loss becomes severe.

• Monitoring data is essential for threshold-based pest management rather than routine pesticide use.

• Review core concepts, definitions, and field-level application points from this lesson.

• Prioritize economic threshold-based decisions and integrated management logic where relevant.