Sterile Insect Technique (SIT) PDF

Genetic control It may be defined as changing the genetics of an insect pest in a way that its further reproduction stopped. Genetic control is a form of biological control of pest species which exploits the insect's mate-seeking expertise to introduce genetic abnormalities (typically, but not nece...

Genetic control It may be defined as changing the genetics of an insect pest in a way that its further reproduction stopped. Genetic control is a form of biological control of pest species which exploits the insect's mate-seeking expertise to introduce genetic abnormalities (typically, but not necessarily, dominant lethal mutations) into the eggs of the wild population. Mating of released sterile males with native females leads to a decrease in the females' reproductive potential and ultimately, if males are released in sufficient numbers over a sufficient period of time, to the local elimination or suppression of the pest population. Hybrid sterility is defined as the inhibition or suppression of the reproductive capacity of F1 or later generation hybrids between genetically different strains or populations, usually belonging to different species. Cytoplasmic incompatibility: can be defined as the failure of a cross to produce any offspring (or only male offspring in haplodiploid species) because of cytoplasmic factors. A lethal mutation is a type of mutation in which the effect(s) can result in death or reduce significantly the expected longevity of an organism carrying the mutation. A chromosomal rearrangement means that pieces of chromosomes are missing, duplicated (there are extra copies), or moved around. The effects vary. They depend on which chromosome pieces are involved and how they are rearranged. Some have no effect, some are incompatible with life, and others are somewhere between. Cell division, or mitosis, is the process by which a mother cell divides its nuclear and cytoplasmic components into two daughter cells. Mitosis is divided into four major phases: prophase, metaphase, anaphase, and telophase. History S. Serebrovskii at Moscow State University, F. L. Vanderplank at a tsetse field research station in rural Tanganyika (now Tanzania), and E. F. Knipling of the United States Department of Agriculture. Hybrid Chromosomal sterility translocations (tsetse) Ionizing radiation lethal mutations  Runner (1916) found that large doses of X-rays applied to the cigarette beetle Lasioderma serricorne (F.) H. J. Muller (1927) showed that ionizing radiation induced visible mutations in Drosophila, Serebrovskii and Vanderplank focused hybridization Most successful AW-IPM programme integrating the SIT in 1950s South-eastern USA of the New World screwworm Cochliomyia hominivorax (Coquerel) 43 years USA, Mexico, and Central America to Panama  1970s , 1st large-scale programme, established, (MFF: Ceratitis capitata (Wiedemann) 1980-1990, MFmelon fly Bactrocera cucurbitae (Coquillett) in Okinawa MFF in Chile, (fly-free zoneby 1995) Argentina also has developed significant SIT-MFF programmes SIT to get rid of various Anastrepha species (northern Mexico) 1967, PBW Pectinophora gossypiella (Saunders) in the San Joaquin Valley of California Codling moth Cydia pomonella (L.), in the Okanagan region of British Columbia  sleeping sickness Tsetse flies nagana Glossina austeni 1997 of the tsetse fly Newstead in Zanzibar, Tanzania, 2001, the African Heads of State and Government committed their countries to rid Africa of this disease PRINCIPLES OF THE STERILE INSECT TECHNIQUE AREA-WIDE INTEGRATED PEST MANAGEMENT AND THE STERILE INSECT TECHNIQUE IPM against an entire pest population within a delimited geographic area, with a minimum size large enough or protected by a buffer zone so that natural dispersal of the population occurs only within this area. Knipling, as cited by Dickerson et al. (1999), stated: Area-wide pest management is the systematic reduction of a target key pest(s) to predetermined population levels through the use of uniformly applied control measures over large geographical areas clearly defined by biologically based criteria. Lindquist (2000) wrote: An area-wide insect control programme is a long-term planned campaign against a pest insect population in a relatively large predefined area with the objective of reducing the insect population to a non-economic status. Thus Knipling (1972) elaborated the basic principle of total population suppression Uniform suppressive pressure applied against the total population of the pest over a period of generations will achieve greater suppression than a higher level of control on most, but not all, of the population, each generation. AW-IPM differs from conventional pest management in several important ways (1) Management of pest populations throughout the ecosystem, while the conventional strategy focuses narrowly on defending the valued entity (crop, livestock, people, buildings, etc.) from direct attack by pests, (2) SIT requires multi-year planning while the conventional strategy involves only minimal forward planning, (3) Utilize advanced technologies, “high-tech”, whereas the conventional strategy tends to rely on traditional tactics and tools “low-tech” (Lindquist 2000, 2001). Benefits of Area-Wide Integrated Pest Management Environmentally, more effective, and more profitable Many producers to pool resources to utilize technologies and expertise Economies of scale can be captured in area-wide programmes Legal Authority for Area-Wide Integrated Pest Management The legal authority to conduct area-wide and other regulatory programmes is absolutely essential, and still evolving Apathy, Outrage, and Area-Wide Integrated Pest Management Invasive Pests, Global Trade, and Area-Wide Integrated Pest Management  Mechanisms of Sterility A sterile insect is defined (FAO 2005) as an insect that, as a result of an appropriate treatment, is unable to produce viable offspring Sterility may be caused by (1) the inability of females to lay eggs (infecundity), (2) the inability of males to produce sperm (aspermia), or inability of sperm to function (sperm inactivation), (3) the inability to mate, or (4) Dominant lethal mutations in the reproductive cells of either the male or female (LaChance 1967; LaChance et al. 1967; Lance and McInnis, this volume These mechanisms may be induced by exposing insects to gamma rays, X-rays, or certain chemicals (Bakri et al) Trend of an insect population subjected to sterile insect releases when the normal increase rate is five-fold  Requirements to Achieve Area-Wide Integrated Pest Management Using SIT The target pest must be a good candidate for suppression The ecology of the target pest must be thoroughly understood. There must be strong stakeholder cohesiveness, good leadership, and commitment to the campaign. An effective and knowledgeable programme leader, supported by an effective organization, is needed. There must be a system of programme review, including external and independent experts. Research and methods-development to backstop the programme are needed. Legal authority is required to execute all aspects of the programme, Examples of Biological Characteristics that Allow, or Increase the Feasibility of, Using SIT Sexual reproduction (exclusively) Methods of mass-rearing are available, or can be developed Species is holometabolous (quiescent pupal stage facilitates sterilization and handling) Males exposed to sterilizing doses of ionizing radiation can compete with wild males for mates Methods are available to monitor released sterile and wild populations Low intrinsic rate of increase Examples of Biological Characteristics that Could Negate or Severely Complicate Using SIT Parthenogenesis Highly synchronous, aggregated, ephemeral mating system (found in many eusocial insects and other groups such as some Ephemeroptera) Extended life cycle, e.g. typical of many cicadas Sterile insects themselves are a serious pest, disease vector, or nuisance pest, such as horn flies, locusts, house flies or cockroaches Migratory behaviour involving long-distance flight and/or movement along weather fronts, as in various moths, locusts, planthoppers and stable flies MASS-REARING FOR STERILE INSECT RELEASE Cost of Mass rearing FACILITY DESIGN AND LOCATION ESCAPES AND ENVIRONMENTAL CONCERNS STRAIN MANAGEMENT PRODUCTION, PROCESS, AND PRODUCT CONTROL DIET SEX SEPARATION MARKING AND STORAGE STERILIZING INSECTS WITH IONIZING RADIATION  Dose Units Rad - Radiation Absorbed Dose Rad is being replaced by the unit called the Gray (Gy) Rem - Radiation Equivalent Man Rem is being replaced by the unit called the Sievert (Sv) 1 Gy = 100 rads 1 Sv = 1 Gy Both 1 Gy and 1 Sv are defined as equal to 1 J kg-1 Gray, Gy milliGray, mGy (= 1/1000 Gy) kiloGray, kGy (= 1000 Gy)  Advantages of using radiation to sterilize insects include Temperature rise during the process is insignificant Sterile insects can be released immediately after processing, irradiation does not add residues that could be harmful to human health or the environment, and radiation can pass through packaging material, allowing insects to be irradiated after having been packaged. In preparation for irradiation, a canister of insects is placed in the irradiation chamber (while it is in the shielded position) of a self-contained gamma irradiator. Depending on the dose rate of the day, the timer on the control panel (lower right) is set to give the desired dose. Chemosterilants added to rearing diets, applied topically to insects, or even deployed in attractant-baited devices in the field efficacies of irradiating and chemosterilizing insects for population control were, in general, similar Most chemosterilants are carcinogenic, mutagenic, and/or teratogenic, leading to environmental and human-health issues Insect resistance to chemosterilants is an additional concern (Klassen and Matsumura 1966). Exposure to ionizing radiation is now the principal method of inducing sterility for AW-IPM  FACTORS MODIFYING INSECT RADIATION SENSITIVITY Environmental and Physical Factors Ambient Atmosphere Oxygen levels affect the sensitivity of insects to radiation Dose Rate Temperature There are some data to suggest that irradiation at reduced temperatures tends to increase the resistance of arthropods to radiation (Rananavare et al. 1991).  Biological Factors Cell Stage and Characteristics The most radiosensitive cells are those (1) with a high mitotic rate, (2) with a long mitotic future (i.e. under normal circumstances, they will undergo many divisions), and (3) which are of a primitive type. It is generally accepted that chromosomal damage (structural and numerical anomalies) is the cause of dominant lethal mutations. Dominant lethal mutations occurring in a germ cell do not cause dysfunction of the gamete, but are lethal to the fertilized egg or developing embryo Chromosome organization can also affect the response to radiation Developmental Stage and Age Diapause Sex, Size and Weight Nutritional State