“GM” in “PM”

Genetic manipulation in pest management (pest population control)

Genetic manipulation in agriculture

• GM on crops• GM on pests

Sterile insect technique / release method (SIT) / (SIR)1. Mass rearing of the target insect species (males)2. Sterilizing the insects with ionizing radiation or chemosterilants.3. Releasing in large enough numbers to reduce the probability of

successful matings in the wild population.

Kniplings Model• The SIT was first described by E. F. Knipling in 1955.• http://instruct1.cit.cornell.edu/courses/ipm444/07Gen

ManPest/mp1.htm

"I wanted to contribute to agriculture in ways other than pulling a cotton sack down the row."

Edward F. Knipling

Some success stories…• Screwworm fly (Cochliomyia hominivorax)- eradicated from the

United States (1950s-90s), Netherland (Curaçao, 1954) and Libya (1990-92)

• Mexican fruit fly (Anastrepha ludens) eradicated from most of northern Mexico.

• Tsetse fly eradicated from Zanzibar (1970–1990s).

• Medfly (Ceratitis capitata)- eradicated from northern part of Chile and southern part of Peru and southern part of Mexico (1970s–80s)

• Sweet potato weevil (Cylas formicarius) eradicated from Kume Island, Okinawa, Japan (1994-99).

Etc.…

Yuval et al., 2010. ISME J

What are the advantages of SIT?• Creates inverse density-dependent feedback, making it

more efficient as the wild population decreases. • The only PM tactic whose fundamental objective is to drive a

wild population to extinction.• Specific • Environmentally-friendly– Does not contaminate natural food chain– No threat/harm to human health has so far been reported

What are the 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.

• Economics. Cost of rearing, sterilizing, and releasing a large numbers of insects can be very high and needs to be justified (EIL).

• Desirability of sterile males. The lab-reared and sterilized males must be equally or more competitive than the native males in mating with the native females. They may become less desirable after many generations and need renewal.

• Knowledge about the pest. reproductive behavior, population dynamics, dispersal, and ecology of the insect.

• Accurate estimation of the native population density• Timing. The development of the lab-reared colony must be synchronous

with that of the wild population. • Resistance. Native females may be able to recognize and refuse to mate

with sterile males.

Inherited / delayed sterility• An alternative genetic strategy to SIT:

– requires fewer insects – requires lower doses of radiation

• Released insects are fertile but their progeny are sterile.• Genetic alterations induced by low dose radiation

– Reciprocal translocations– genetic transformation with a conditional lethal trait

http://instruct1.cit.cornell.edu/courses/ipm444/07GenManPest/mp4.htm

The concept of Population displacement• What may be the issues of completely eliminating a pest

species from an ecosystem?– upsets the balance at higher trophic levels, food webs– secondary pest

• The idea of Population displacement is that we are not just eliminating the native pest species (AA) but replace it with a genetically translocated counterpart (TT), in which AA and TT are both fertile– Only the hybrid (AT) would be sterile– Replacement occurs If TT >> AA in the wild

• TT strains would have more preferable traits– E.g. less damaging to crop, more sensitive to insecticides,

environmental stress, "booby trap" chemicals.

Dominant Conditional Lethal Mutation• Release of GM insects with dominant, conditional lethal trait • Example: