Rainfed rice - IRRI books - International Rice Research Institute

RAINFED RICE A SOURCEBOOK OF BEST PRACTICES AND STRATEGIES IN EASTERN INDIA
Merits
Merits and demerits of insecticide control
Pesticides are the only practical
control measure at the expected
threshold level.
Increases farmers’ income.
Without pesticide, many commonly
used quality food products could not
have been produced commercially.
Pesticides are useful for protecting
health and property.
Demerits
Many insect and mite species have developed
resistance to insecticides and acaricides.
Provides temporary reduction of pest population,
which often resurges, necessitating repeated
application.
Outbreak of secondary pests, resulting from the
destruction of natural enemies.
Undesirable effects on non-target organisms,
such as honeybees, fish, wild animals, etc.
Residue hazards for crop and direct hazards
during operation.
The problem of insect resistance to insecticides
It is a biological property of an organism to withstand the poisoning action
of a pesticide. A resistant organism functions, develops and reproduces
normally in a medium containing a poison.
Various kinds of resistance
NATURAL RESISTANCE: This kind of resistance appears and exists independently of the use of
chemical means.
It is due to the biological feature of a definite species and can be successfully controlled
Specific
by selecting the appropriate pesticide.
Sexual
Phase or stage
Seasonal,
temporary and
age
In most cases, the females of the species have higher resistance. This is overcome by
choosing relevant doses.
This is the phase/stage of development of the insect. Larval and adult stages of insects
are the most sensitive to insecticides. High resistance is a feature of egg and pupal stages.
The resistance within a single stage (phase) of development changes depending on age,
time of day and year (season). Proper choice of insecticide and strict observance of the
optimal periods are the best ways to control this resistance.
SPECIFIC (ACQUIRED) RESISTANCE: It signifies the ability of a harmful insect to survive and reproduce
in the presence of an insecticide that previously suppressed its development.
Individual
Group
Cross
This kind of resistance is encountered rarely and is due to the activity of narrowly
specialised enzymes decomposing toxic substances.
This is the resistance of insects/pests belonging to the same group to two or more
insecticides with a similar structure and mechanism of action. Resistance is due to:
slower penetration of the poison and faster excretion;
rapid detoxification of an insecticide because of higher activity of the enzymes or
appearance of specific enzymes;
a different penetrability of the shell of nerve cords; and
increased lipid contents in the body of the resistant insects.
This is resistance to two or more insecticides of different groups in both the chemical
structure and mechanism of action that appear after the use of one pesticide.
Insecticide resistance prejudices the usefulness of insecticides in future pest control programs.
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