Genetic Control and Hybrid Sterility

Study Notes

Inhibits or suppresses the reproductive capacity of hybrid offspring.
Occurs between genetically different strains or populations, often of different species.

Failure of a cross to produce offspring (or only male offspring in haplodiploid species).
Caused by cytoplasmic factors.

Mutation that results in death or significantly reduced longevity of the organism.

Serebrovskii, Vanderplank, and Knipling were pioneers in this field.
Runner (1916) discovered that X-rays affected reproduction in the cigarette beetle.
H.J. Muller (1927) identified the role of ionizing radiation in inducing mutations in fruit flies.
The Screwworm Project (1950s) involved releasing sterile screwworms, leading to the elimination of the pest in parts of the US and Mexico.
The Mediterranean Fruit Fly (1970s) saw the implementation of large-scale sterile insect release programs.
Other notable examples include:
- Melon fly control in Okinawa (1980-1990)
- Eradication of the Mediterranean Fruit Fly in Chile (by 1995).
- Control of Anastrepha species in Northern Mexico.
- Pectinophora gossypiella control in California (1967).
- Codling moth control in British Columbia.
Tsetse fly control aims to eliminate sleeping sickness and nagana in Africa.

A form of biological control.
Focuses on the whole pest population within a specific geographical area.
Aims to reduce populations to non-economic levels.
Basic Principle of Total Population Suppression: uniform suppressive pressure over multiple generations leads to better control.

AW-IPM aims to manage pests in a whole ecosystem.
Involves multi-year planning and advanced technologies.
Benefits include:
- Environmentally friendly
- More effective
- More profitable for producers.
- Allows for resource pooling and economies of scale.
Legal authority is crucial for implementing AW-IPM programs.

Advantages:
- Sexual reproduction only
- Methods for mass rearing are available
- Quiescent pupal stage makes sterilization and handling easier
- Sterile males compete with wild males for mates
- Methods for monitoring sterile and wild populations exist
- Low intrinsic rate of increase.

Challenges:
- Parthenogenesis (reproduction without fertilization)
- Synchronized and ephemeral mating systems
- Extended larval cycles (e.g., cicadas)
- Sterile insects may themselves be a pest, disease vector, or nuisance
- Migratory behavior.

Cost: a significant factor in sterile insect release programs.
Facility Design and Location: key considerations for mass rearing.
Escapes and Environmental Concerns: minimizing environmental impacts.
Strain Management: maintaining quality and effectiveness of the sterile insect strain.
Production, Process, and Product Control: ensuring consistent and high-quality insect production.
Diet: providing adequate nutrition for insect growth and development.
Sex Separation: separating males and females for sterilization and release.
Marking and Storage: identifying and storing sterile insects before release.

Dose Units:
- Rad and Gray (Gy)-measure radiation absorbed dose
- Rem and Sievert (Sv)-measure radiation equivalent man
Advantages of radiation sterilization:
- Minimal temperature rise during the process.
- Insects can be released immediately after irradiation.
- No harmful residues.
- Packaging material does not interfere with irradiation.
Process: Canisters of insects are placed in shielded irradiation chambers.
Chemosterilants:
- Alternate sterilization method.
- Concerns about carcinogenicity, mutagenicity, teratogenicity, and insect resistance.

Environmental and Physical Factors:
- Ambient Atmosphere (oxygen levels)
- Dose Rate
- Temperature.
Biological Factors:
- Cell Stage and Characteristics (e.g., mitotic rate).
- Chromosome organization.
- Developmental Stage and Age.
- Sex, Size, and Weight.
- Nutritional State.