2. 2
Reproductive/ autocidal / genetic Control
“Reducing insect population by lowering their reproductive potential”
Sterility among progeny
Reducing fecundity
Reducing survivorship
Methods of Insect Sterility
1. High wave radiations: causes chromosomal breakage
2. Chemosterilization: Alkylating agents (damage genetic sperm material),
phosphorous amide, tuazines, antimetabolites
3. Other tactics
Condition lethal: low temperature fitness factor manipulation
3. 3
Reproductive/ autocidal / genetic Control
3. Other tactics
Inherited Sterility: 9:1 sterile: fertile male: female ratio in one generation
Hybrid sterility: Horse × donkey ---- sterile mule,
Heliothis virescens ×H. subflexa
Cytoplasmic incompatibility: crossing of different populations
Chromosomal rearrangement: insects with genetic defects
Meiotic drive mechanism: unequal recovery of homologous chromosomes,
more male insects are produced
5. 5
Sterile insect technique (SIT)
1. Sterile Insect Technique (SIT) was initiated by E.F. Knipling and R.C.
Bushland in the 1930s
2. SIT was first described by Edward. F. Knipling in 1955.
3. They worked with the screwworm fly, a devastating pest of cattle in
North America
4. The first successful use of SIT to control screwworm was on the
island of Curaçao in 1953.
5. SIT is a method of pest control using area-wide inundative releases
of sterile insects to reduce fertility of a field population of the
same species” (FAO, 2005).
6. Objective of SIT : “Eradication of pest not merely
suppression”
6. • Rearing Facility for SIT
1. Selection of artificial diet
2. Waste disposal
3. Biosecurity in a pest free area
Mediterranean fruit fly mass-rearing
facility in elpino Guatemala.
Heat treatment of eggs Racks of cages with adult flies Larval rearing trays
7. 7
Techniques for Release
1. Aeril release-using aircrafts
2. Ground release
3. If the release is delayed ,survival can be increased by chilling treatment
1. Aircrafts 2. All-Terrain Vehicle (ATV)
9. 9
Successful Eradication of Screwworm
In 1954, the technique was used to completely eradicate screwworms from the
176- square-mile (460 km2) island of Curaçao.
Screwworms were eliminated in a span of only seven weeks, saving the
domestic goat herds that were a source of meat and milk for the island people
During the 1960s and 1970s, SIT was used to control the screwworm population
in the United States.
The 1980s saw Mexico and Belizium eliminate their screw worm problems
through the use of SIT.
In 1991, Knipling and Bushland's technique halted a serious outbreak in northern
Africa.
10. 10
Advantages of SIT
Specific
Environment friendly: does not contaminate natural food chain. No threat to
human health is reported so far
The only IPM tool whose fundamental objective is drive a wild population to
extinction.
Limitations of SIT
Economics: Cost or rearing insects, sterilizing and releasing a large no of insects
may be very high
The lab reared sterile males must be equally or more competitive to the native
males in mating with the native females; as they become less desirable after many
generations and need renewal
11. 11
Limitations of SIT
Geography: The eradication zone must have either natural barriers ( e.g., oceans,
deserts, mountains) or defensible borders to prevent or reduce the immigration of
the target pest from outside.
Resistance: Native females may be able to recognize and refuse to mate with
sterile males
Knowledge about the pest reproductive behaviour, population dynamics,
dispersal, and ecology
Application at Right time: The development of lab-reared colony must be
synchronized with the wild population.
Continued….
12. 12
Conclusions:
1. SIT is arguably the most ecologically-compatible means of pest control in
existence time.
2. It is not a stand-alone technology, but should be integrated with other pest
management technologies, such as bait application and sanitation, in an area-
wide program.
3. It is the dominant component of an integrated pest management (IPM) strategy.
4. Close collaboration of IAEA (International Atomic Energy Agency) and FAO
(Food and Agriculture Organization) over the past four decades is succeeding in
developing and implementing SIT as an effective tool.
