resistance management

1. STRATEGIES FOR
PESTICIDE
RESISTANCE
MANAGEMENT
Submitted to:
Dr. Rakesh kumar
Dr. Tanuja Banshtu
Submitted by:
Harmanjot Singh
H-2021-04-D
ASSIGNMENT

2. WHAT IS PESTICIDE RESISTANCE ?
◦ Pesticides have been used by humans for over 400 years to control
pests
◦ Over time populations of pests can evolve to become less responsive
to the pesticides that are used to control them
◦ When insect pest populations can no longer be controlled by a dose
of pesticide which were used to control them is termed as Pesticide
resistance
◦ However, for it to be considered true resistance, the resistant pests
must be able to pass on the ability to resist the pesticide to their
offspring
◦ Insect pests have the capacity to develop resistance to all forms of
pesticides including: synthetic chemicals, biological extracts,
proteins, peptide and pheromones
IRAC Technical definition:
“A heritable change in the
sensitivity of a pest
population that is reflected
in the repeated failure of a
product to achieve the
expected level of control
when used according to the
label recommendation for
that pest species’’

3. The rate of development of resistance in a population depends upon 4
factors
The
frequency
of resistant
genes
present in a
population
The nature of
genes (single
or multiple;
dominant or
recessive)
The intensity
of the
selection
pressure of
the toxicant
The rate of
breeding of
the species

4. Resistance is categorized into cross and multiple resistance.
CROSS RESISTANCE
It is defined as resistance from two or more
pesticides via a single mechanism of resistance.
- Cross-resistance within a mode of action group
◦ In most cases resistance to a pesticide also confers
resistance to pesticides from the same group.
◦ However, there can be differences in the level of
resistance between pesticides even within the same
group. This is called partial cross-resistance
- Cross-resistance between mode of action groups.
◦ In rare cases pesticides which don't have the same
mode of action, but have similar molecular
structural components may be metabolized by a
single enzyme
MULTIPLE RESISTANCE
It is defined as resistance to two
or more pesticides via multiple
mechanisms of resistance in a
single insect.

5. Examples of Cross and Multiple Resistance
in insects
Cross Resistance
◦ The Colorado potato beetle, Leptinotarsa
decemlineata (Say), has developed Cross
resistance to many insecticides used for
its control, recently including
imidacloprid, a neonicotinoid compound.
(Mota‐Sanchez, et al. 2006)
Mutiple Resistance
◦ The Diamond back moth, P. xylostella
selected in the field with Bt formulations
(containing Cry1A and Cry1C toxins) and
further selected with Cry1C in the
laboratory, developed high levels of
resistance to Cry1A and moderate levels
of resistance to Cry1C (Liu and
Tabashnik, 2003).

6. MECHANISM OF RESISTANCE
◦ Resistance occurs through mutations in the genetic make-up of the insect.
◦ DNA which is made up of a chain of paired nucleotides is often described
as the genetic 'instruction book' for constructing living organisms.
◦ However, the replication of DNA is not a perfect process and errors can
occur. These errors are called mutations.
◦ As the DNA provides the instructions for the development and function
of the insect, a mutation can result in a change in insect physiology or
biochemistry.
◦ The mutation may result in the insect becoming less susceptible to a
pesticide and this provides it with a competitive advantage when the same
pesticide is applied again.

7. PRE ADAPTIVE MECHANISM OF RESISTANCE
The Pre adaptive resistance is due to the genetic variations present in the
population.
For example – In Housefly, the resistance to DDT is due to recessive gene
Kdr (Knockdown resistance) located on chromosome -3. This gene is
responsible for nerve insensitivity found in certain DDT resistant strains.
TARGET SITE RESISTANCE
Pesticides generally have a specific site of action within an insect, this is
usually a receptor protein. When a mutation occurs in the genetic code for
the receptor protein, it can modify the shape of the protein and prevent the
pesticide from interacting at the site of action and thus confers resistance.
This type of mutation is called target site resistance.

8. ◦In Post adaptive resistance are of different types
POST ADAPTIVE MECHANISM OF RESISTANCE
Physiological Behavioural
LIPID CONTENT – The
insects containing higher lipid
content are comparatively more
resistant than normal ones. As,
lipids pick up pesticides like
organo chlorines and deposit
them in the tissues.
For ex. Brown (1971) reported
that the lipid content was
higher in the resistant flies from
DDT particularly in their
ganglia and tarsi.
DETOXIFICATION OF INSECT-
CIDES TO NON TOXIC META-
BOLITES - The DDT resistant
insects have the ability to detoxify
DDT DDE
Although not common, there are
examples where mutations have
altered the natural behaviours of
the insect, reducing exposure of
the insect to the pesticide and
allowing it to survive
For ex. The codling moth rejects
the first bite prior to the
penetration in the insecticidal
sprayed fruit.
Dehydrochlorination
Glatuathione

9. How does Pesticide resistance become a problem ?
◦ In most circumstances a resistance mutation may not have
any impact. The insect with a mutation continues to live
and reproduce like other insects of its species
◦ If a pesticide is applied that is not affected by the resistance
mutation, both susceptible and resistant insects would be
controlled
◦ However if a pesticide is applied that is affected by the
resistance mutation only the susceptible insects would be
controlled and the resistant individuals would survive and
then go on to reproduce

10. How does Pesticide resistance become a problem ?
• In any given agricultural field or glasshouse environment there could be hundreds to millions of insect
pest present and there may be several mutations present that confer resistance to different pesticides.
• When an pesticide is sprayed, the insects which carry the resistance mutation survive and become more
frequent in the population.

11. How does Pesticide resistance become a problem ?
◦ The surviving resistant insects continue to live and breed and passing on their mutation to their
offspring.
◦ Eventually the population may increase to a point where control will be once again necessary.

12. How does Pesticide resistance become a problem ?
◦ The decision on what to do next is critical for both the management of the insect pest and in
managing resistance.
◦ If the same pesticide is used on the next generation of pest insects, then the effectiveness of
the pesticide is likely to be reduced and even more resistant pests will survive.
A control program with repeated use of same pesticide mode of action can quickly change a
once manageable insect pest population into one that is very difficult to control.

13. How can we prevent Pesticide resistance becoming a problem ?
◦ In order to prevent insect pests with a resistance mutation from becoming too dominant in a population.
Pesticides with different modes of action should be used in sequence or rotation across insect
generations.
◦ This method of pest management slows the selection process and delays resistant insects from
increasing in frequency.
◦ The more frequently the same Pesticide is used the faster the resistance mutation is selected.

14. Managing insect pest resistance
◦ Insects may occur at different times within a crop environment.
◦ When designing a strategy to control the insect pests it is important to consider resistance management.
◦ IRAC recommends segregating the crop cycle into 'windows of application’.
◦ Each window of application should be as long as it takes for the pest to go through one generation (egg/juvenile to
adult).
◦ It's not always easy to determine the generation time of an insect, so in the absence of this information. IRAC
recommends using a 30 day window for most pests, but a 15 day window for aphids and mites.

15. Managing insect pest resistance: Single Pest
◦ It is recommended that insecticides with the same mode of action or with cross resistance are not used in
adjacent or sequential windows.
◦ However the same mode of action can be used in alternate windows.
◦ For best resistance management practice multiple effective modes of action should be utilized in a program

16. Managing insect pest resistance: Multiple Pest
◦ A resistance management strategy for a single pest can be easy to design and implement, but the reality is that
there is often more than one pest present in a crop.
◦ In a multi- pest environment, application windows have to be modified to include each pest.
◦ It is important to note that more than one application of the same mode of action can be made within a
window, as long as the residual effects of the pesticide do not exceed the length of the window.

17. Why is it important to manage resistance
SAVES MONEY
• Maintains the most effective products for longer periods.
• Reduces the need to switch to more expensive or less preferred methods of control.
• Maintains yield expectations and ensures sustainable production.
SAVES TIME
• Less time spent in the field as the need for repeated applications is reduced.
• Less effort and worry trying to achieve effective pest control.
ENHANCES SAFETY OF PRODUCE
• Reduces need for repeat Pesticide application, minimizing residue risk on produce
PROTECTS YOUR HEALTH AND LAND
• Resistance management practices increase worker safety and protects the
environment.

18. General RM Strategies

19. ROTATION OF THE PESTICIDE
◦ The same pesticide should not used for a long time particularly when resistance
has been detected.
◦ Insects resistant to one pesticide may not be resistant to another.
◦ After a time lag the lost susceptibility to the first pesticide returns.
◦ Rotations of compounds from different MoA groups provide sustainable and
effective RM for insect and mite pests.
◦ This ensures that selection from compounds in the same MoA group is
minimised and resistance is less likely to evolve.

21. USE OF SYNERGISTS
◦ Resistance to pesticides in insects develops due to their ability to degrade the pesticides into inactive
compounds by detoxifying enzymes.
◦ To over come this resistance compounds that can block the action of the detoxifying enzymes should be
added to the pesticides.
◦ These inhibitory compounds are called synergists which allow the pesticide to function normally only by
blocking their inhibitory enzymes and do not in reality enhance the potency of the pesticides.
◦ Synergists are among the most straight forward tools for overcoming metabolic resistance because they
can directly inhibit the resistance mechanism itself.
◦ Synergists can be less active on predators than on pests.
◦ Ex – Piperonyl butoxide serve to synergize many pesticides like DDT, carbamates etc against houseflies
and other insect pest.
◦ Malathion resistance is overcome by use of synergists such as triphenyl phosphate.

22. MIXTURES AND ALTERATION
◦ Mixtures increase the level of target pest control and the range of pests controlled.
◦ Most Mixtures are not primarily used for purposes of Insect Resistance management
(IRM).
◦ A mixture of two pesticides with and independent action against the resistant strain give
good control and delays resistance
◦ For Ex – as whiteflies developed resistance against synthetic pyrethroids on cotton, mixture
of cypermethrin and profenfos is used to overcome the problem.
◦ Alteration of pesticides with each generations of insect delays development of resistance.

23. NEGATIVELY CORRELATED PESTICIDES
◦ It has been observed that resistance to one pesticide leads to the enhanced susceptibility to
another pesticide.
◦ Occasionally the development of resistance to one compound have the reverse effect by
making a population more susceptible to a newly introduced compound.
◦ For eg - Cyclodiene resistant boll weevils are found to be susceptible to Malathion.
◦ DDT resistant houseflies are also susceptible to Malathion hence such combinations should
be discovered and used.

24. USE OF INSECT HORMONES IN INSECTICIDE
RESISTANT MANAGEMENT
◦ Just as pheromones modulate insect behaviour, hormones regulate growth and
reproduction in insects.
◦ Both these processes can be interfered with by providing exogenous hormones
at wrong times that is when they are not needed by the insect system.
DEVELOPMENT OF NEWER PESTICIDES
◦ There should be a constant attempt to search for newer pesticides.
◦ This will make a large number of pesticides available for substitution when
particular pesticides fails to kill.

25. JUDICIOUS USE OF PESTICIDE
◦ Indiscriminate use of Pesticides leads to the development of resistance.
◦ Need based insecticidal sprays should be taken up when the pest population reaches
ETL.
◦ Selective Pesticides should be sprayed using proper dose and right equipment.
USE OF INSECT PHEROMONES
◦ Pheromones regulate the insect behaviour.
◦ By using of the sex pheromones insects could be driven to poison baits and they will die.
◦ By providing the aggregation pheromones they could be driven to the wrong host plants
where they would starve and die.

26. INTEGRATED APPROACH
◦ An integrated approach to the control of insect pests will reduce the application of the
pesticides which in turn will lower pesticides pressure on the insects under such a condition
genes governing resistance may not get activated or may take a longer time to do so and keep
resistance postponed for a period of time.
CROP
PRODUCTION
•CULTURAL CONTROL
•BIOLOGICAL CONTROL
•MECHANICALCONTROL
•LEGAL CONTROL
•CHEMICAL CONTROL
•PHYSICAL CONTROL
LESS
RESISTANCE
•IN THE IPM WE ARE DOING THE LESS
DUMPING OF THE PESTICIDES
•NEED BASED APPLICATION
•AVOIDING THE RESISTANCE DEVELOPED
PESTICIDES
•USE OF RECOMMENDED DOSES
IPM

27. Case Study

28. THANK YOU

29. BIBLIOGRAPHY
◦ Prasad T.V. Handbook of Entomology. 3rd ed. ecology causes of pest out break. pp 127-172.
◦ Readdy D.S. Applied Entomology. 2nd ed. of environmental studies, York university. pp 353 – 373.
◦ Gupta HCL. 2022. Pesticides: Toxicology and Uses. 5th ed. pp 177-300
◦ https://irac-online.org/