presentation on applications of life tables in insect pest management

2. USE OF LIFE TABLES IN INSECT PEST
MANAGEMENT
• Submitted to:
Dr. vv Belavadi
Prof. Agril.Entomology
G.K.V.K Bengaluru
• Submitted By:
Chidananda.R
PALB-4098

3. DEFINITION
• Deevey(1947) “is a concise summary of
certain vital statistics of a population, whose
members start life together.
Or
• A ‘life table’ is a kind of “bookkeeping system”
that ecologists often use to keep track of
stage specific mortality in the populations
they study.

4. • A table describes for the successive age intervals
the number of deaths, remaining survivors, rate of
mortality and expectation of further life.
• To create life table an ecologist follow the life
history of many individuals in a population.
Keeping a track of how many offspring each
female produces, when each one dies and what
caused its death.

5. • After amassing data from different
populations, different years and different
environment conditions, the ecologist
summarizes this data by calculating average
mortality within each developmental stages .

6. ROLE OF LIFE TABLES :
• Study of factors to determine the need to the
need to modify the life system of pest with a
view to reducing its number below ETL.
• Study of applied ecology which involves
application of biological knowledge for
achieving desired populations.

7. • Determining the key mortality factor and
predicting the appearance in future.
• Dividing pest control procedures that suits the
available technology compatible with the
economic and environment quality requirement .
• ETL gives for timing application of need based
application of insecticides. Estimation of intensity
of pest population.

8. Importance of life tables:
• Life tables describes for the successive age
intervals the deaths, remaining survivor, rate of
mortality and expectation of further life.
• Life table provides an important tool in
understanding their life cycles.
• By this technique we can determine the
mechanical relationship of various
environmental factors and find out the key
factor that accounts for large part of the
change in population size.

9. • Especially useful approach in entomology
where developmental stage are discrete and
mortality rates may vary widely from one life
stage to other.
• To know when population suffers high
mortality, this is usually the time when it is
most vulnerable.

10. Life tables are two types
• a) age-specific LT or horizontal LT :
It is based on the fate of a real cohort, the
individuals belonging to a single
generation. The population may be
stationary or fluctuating.

11. • b) time-specific LT or vertical LT:
It is based on the fate of a imaginary
cohort found by determining the age
structure, where there is a considerable
overlapping generations. Age
determination is a pre-requisite for time-
specific LT.

12. For preparing a life table for the natural
population of an insect, the following
columns are required.
• B = age interval at which the sample was
taken in units of time (days, weeks etc)
• lx = Number surviving at the beginning of
age class ‘x’ (usually out of 1000 born
• dx = Number dying during at age interval
stated in the ‘x’ column.
• Dfx =The mortality factor responsible for
‘dx’.
• 100qx = percentage mortality. Sx = survival
rate within the age interval ‘x’.

13. Ex : In a hypothetical insect population, an average female
will lay 200 eggs before she dies. Half of the eggs (on
average) will be consumed by predators, 90% of the larvae
will die from parasitisation and 3/5th of the pupae will freeze
to death in winter. :
Develop
mental
stage
Number
alive
mortality
factor
Number
dying
%
mortality
Egg 200 Predation 100 50
larva 100 parasitism 90 90
pupa 10 freezing 06 60

14. Causes of mortality :
• Low vitality (by envi. Factors ).
• Ageing.
• Accidents.
• Physiochemical conditions (temperature).
• Natural enemies. (predators, parasitoids,
pathogens) .
• Shortage of food.
• Shelter.

15. Applications of life tables:
• The weakest link in the life cycle can be
determined and made use of to control pests.
• The effect of most effective biotic factors
causing death of the pest can found out and
used effectively.

16. • Field life table studies on natural enemies can
help in determining the cause of their failure
in field information can help to find out the
best release techniques.
• Field life table studies predator can help in
identifying their natural enemies which can be
manipulated to exploit maximum potential of
predators.

17. • Based on survivorship curves one can
operate control measures when the mortality
factors operating slow and thus can obtain
economic results.
• It provides useful information on their
mortality factors, information thus obtained
can be incorporated in mass production
techniques and make it more efficient.
•

18. • Studies on pest and natural enemies may
provide exact time of release of predator and
parasitoid and utilize them to their best
potential.
• Life table studies on the weeds can yield
information on the most effective natural
enemies which in turn can help to make
decision on import, colonization of weed
insects or weed pathogen.

19. Conclusion
• A ll the ‘lx’ and ‘dx’ values in the life table
indicate the density of individuals per unit
of the host or habitat. Life tables have to
be prepared for different populations of
the same spp throughout its range of
occurrence to have a representative
view. Measurements have to be made on
density, mortality and associated factors
in different parts of the habitat.

20. Thank you