ECONOMIC IMPORTANCE, ECOLOGY.pptx

All insects are not harmful, those harmful
are not harmful unless their population
density crosses certain limit (ETL).
(Economic importance of insects lies more
in their harmful effects than beneficial
effects. Higher the status of an insect as
pest, more important that insect is

Both biotic and abiotic factors influence the
population of a particular insect, hence, it is
very important to understand the role of these
factors on the increase or decrease of the pest
density for the effective management of that
particular insect species.

Ecology: It is the Study of complex interactions
between living organisms and nonliving environment
in a particular place.
Ecosystem: The complex interacting system between
living and nonliving factors is called as ecosystem.
Existence and abundance of a species is determined
by biotic and abiotic factors, besides the genetic
makeup of the species.
Biotic factors: Living factors like competition,
predators, parasitoids, etc.
Abiotic factors: Non living factors like temperature,
RH, photoperiod, etc.

Important components responsible for
population growth:
Physical environment (abiotic factors),
food, space, population itself, other
species.
All these components act on the
population through the pathways of
natality, mortality and dispersal.

Characteristics of a population:
Density, natality, mortality,
dispersal, dispersion, age
distribution, population growth

Density: Number of individuals per unit area or
space occupied.
Crude density: Number of individuals per unit
of total space.
 Ecological density: Number of individuals per
unit of habitat space i.e. space occupied by the
population.

Natality: Number of new individuals produced
per unit time i.e. birth rate.
Absolute natality/ physiological natality:
Theoretical maximum number of individuals
that can be produced under most ideal
conditions.
 Ecological natality: Number of individuals
that can be produced under specific
environmental conditions.

Mortality: Number of individuals dying in a
given population in a given period of time.
Minimum mortality: Mortality of
individuals under most ideal or non limiting
conditions.
Ecological mortality: Mortality of a
population under specific environmental
conditions.

Dispersal: The movement of individuals in to or out of the population
 Immigration: Movement in to the population.
 Emigration: Movement out of the population.
 Migration: Mass movement of the entire population. Such
movements are generally seasonal or periodical.
ROLE OF DISPERSAL IN POPULATION DYNAMICS:
Helps in shaping the population growth form by supplementing
mortality and natality
New or unpopulated areas are colonized.
Helps to introduce genetic variability through interchange between
populations
Leads to an increase in the range of species
Dispersion: Distribution of individuals within a
population at a particular time

Age distribution: Relative proportion of
individuals of different age groups of a
population is called age distribution or age
structure.
More young individuals: population is
expanding
More older individuals : population is
declining
Even distribution of various age groups means
stationary population

Population growth occurs due to the interplay of
biotic potential and environmental resistance
Biotic potential: Inherent property of
individual to reproduce and survive i.e. to
increase in number
Environmental resistance: It is the sum total
of environment‟s limiting factors that prevent
the biotic potential from being realized

FACTORS INFLUENCING PEST POPULATIONS:
Abiotic factors (Temperature, humidity, light)
Biotic factors (Food, predators, parasitoids, pathogens)
Temperature: Affects the following parameters of individuals of population
( Endocrine system Growth Development, Reproduction)
Humidity:
Normal development and feeding activity.
By encouraging diseases.
Excessive body moisture during winter may reduce its capabilities to
withstand low temperatures.
Light:
Orientation, rhythmic behaviour, bioluminescence, periodicities of
occurrence and periods of inactivity.
 Light acts as stimulus for insects to synchronize and regulate their life cycles
with change in seasons.
Influences the motor activity rhythm of insects such as locomotion, feeding,
adult emergence, mating, oviposition, and also moulting and growth in some
species.

Biotic factors:
Food:
o Food quality and quantity affects growth, development, survival,
longevity, reproduction, distribution, etc.
o When the food is in short supply there is intraspecific or interspecific
competition.
o Competition acts in density dependent manner.
o Food supply may be affected by many factors
Natural enemies: Predators, parasitoids and entomopathogens like
bacteria, fungi, viruses, nematodes, rickettsiae, etc.
Natural enemies act negatively on insect populations.
Influence is variable because their own populations are influenced by
various environmental factors.
Predators generally respond to increase in pests population through:
o Numerical response (By increasing their number)
o Functional response (By increasing the consumption)

Avoidance of economic damage with minimum affects on the
environment
 IPM: In simple language IPM is the utilization of all possible control
tactics to suppress the pest population below economic injury level with
minimum adverse impacts on environment.
 Economic Injury Level (EIL): It is the minimum pest population which
causes the economic damage.
Economic damage: The damage caused by the pest to a crop which
justifies the cost of control or in other words it is the damage equal to
the cost of control.
 Economic Threshold Level: It is the pest population where control
measures should be initiated to prevent the pest population in reaching
the EIL.
ECOLOGICAL BASES OF PEST MANAGEMENT:
CONCEPTS OF IPM

Measurement of pest population intensity.
Determining the influence of natural
enemies on the pest population
Crop loss assessment by the pest
Monitoring of pest population for decision
making.
Basic necessities in IPM:

COMPONENTS OF IPM:
Cultural control
o Tillage
o Planting and harvesting time
o Sanitation o Plant diversity
o Trap cropping
o Crop rotation
o Nutrient and water management
Mechanical control
o Hand picking
o Exclusion by screens and barriers
o Clipping and pruning
Physical control
o Hot and cold treatment
o Light trapping

Legal control
Legislation for foreign quarantine to prevent the
introduction of new pests from abroad.
 Legislation for domestic quarantine to prevent the
spread of established pests within country or a
particular state.
Legislation for notified campaigns of control against
pests.
Legislation to prevent the adulteration and
mishandling of insecticides or other devices used for
the control of pests.

Biological control
Predators: Lady bird beetles, syrphid flies, lace wings, etc.
Parasitoids:Trichogramma spp, Apanteles spp, Bracon sp,
etc
Bacteria: Bacillus thuringiensis
Viruses: NPVs and GVs have been successfully used.
Fungi:
Beauveria bassiana: Against beetles and caterpillars
Metarhizium anisopliae: Against beetles and
caterpillars
Nomuraea rileyi: Against caterpillars
Verticillium lecanii: Against sucking pests
Paecelomyces sp: Against sucking pests

Chemical control
 Semiochemicals
Other components:
 Growing resistant cultivars
 Use of sex pheromones for monitoring,
mass trapping, mating disruption and auto confusing
the target pests.
 Use of botanical pesticides especially neem
based insecticides.
 Need based, safe and judicious use of synthetic
pesticides.

 It provides sustainable control of the pest and also
adds to sustainable crop productivity.
 It is economically viable and is affordable by
marginal farmers.
It is environmentally safe.
Less health hazards.
 Social and political stability
Quality produce with minimum pesticide residues
and hence will enhance the export of agricultural
commodities
Advantages of IPM

For effective management of any pest
species, it is important to make timely
prediction/ forecasting of the population
buildup. Quantification of populations is
another important aspect.

Pest Monitoring :
Monitoring phytophagous insects and their natural enemies is
a fundamental tool in IPM - for taking management decision
Monitoring - estimation of changes in insect distribution and
abundance
-information about insects, 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

it is the prediction of severity of pest population which can cause
economic damage to the crop. The systematically recorded data on pest
population or damage over a long period of time along with other
variable factors, which affect the development of pest, may be helpful in
forecasting the pest incidence.
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

The forecasting of pests guides the farmers about the timing and
biology of insect incidence, and to eliminate blanket applications,
reduce pesticide amounts, and achieve quality results.
The farmers can take to timely action of applying various pest control
measures to harvest maximum returns.
Types of Pest Forecasting: Pest forecasting may be
divided into two categories, viz., short-term
forecasting and long-term forecasting.
1.Short-Term Forecasting:
2.Long term forecasting

1.Short-Term Forecasting:
These may cover a particular season or one or two successive
seasons only. The pest population is sampled from a
particular area within a crop using appropriate sampling
technique and the relationship is established between
weather data and progress in pest infestation.
1. Long term forecasting
These forecasts are based on possible effect of weather on the pest
population and cover a large area.
The data are recorded over a number of years on wide seasonal range
and from different areas.
Long-term forecasting is based on knowledge of the major aspects of
the pest insect’s lifecycle, and of how it is regulated.

The data recorded are analyzed and models are
developed based on the available information.
The models help in forecasting pest population in
various geographical areas based on common
weather parameters.

 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 effect of new cropping pattern and varieties on
pest
Objectives of Pest Surveillance

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
Survey
Conducted to study the abundance of a pest species
Two types of survey - Roving survey and fixed plot survey
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

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
Qualitative survey - Useful for detection of pest
Quantitative survey - Useful for enumeration of pest
Sampling Techniques

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

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
 proper 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
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
c. Degree of injury per insect
d. Crop susceptibility to injury
Secondary factors
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
- 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
Weather, soil factors, biotic factors and
human social environment These tertiary
factors cause change in secondary factors
thereby affect the ETL and EIL
Tertiary factors

ECONOMIC IMPORTANCE, ECOLOGY.pptx

ECONOMIC IMPORTANCE, ECOLOGY.pptx

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