Chemosterilants have been often referred to as agents producing dominant lethal mutations in the germ cells of treated organisms. Recent studies of the mode of action of various chemosterilants in insects indicate that there are many other pathways by which chemical compounds can induce sterility in insects. Although the genetic mechanism still appears to be the most plausible explanation of the mode of action of many chemosterilants in male insects, other alternatives must be considered for explaining the chemical sterilization of female insects. The elucidation of the biochemical processes leading to sterility is important not only because chemical mutagenesis was first discovered in an insect (Drosophila melanogaster); chemicals offer a flexible, and sometimes the only available, method of inducing sterility in economically important insects which can be utilized in the sterile-male technique of insect control. As distinct from radiation, chemosterilants can be utilized for sterilization of the naturally occurring pest populations. In sterile- insect release programmes, chemosterilants become of importance whenever secondary radiation effects interfere with longevity and sexual competitiveness of radiation-sterilized insects. The understanding of the mechanism and mode of action of chemosterilants will aid in the search for new types of effective compounds and in designing new materials specific to insects or even to individual insect species. The sterility principle in pest control has thus far been successfully applied only to insects, but vertebrate pests will certainly be considered in the future. Chemosterilants may be the most effective tool for sterilization of vertebrate organisms. (author)
唐桦; 郑哲民; 杨卫东; 姜文胜; 康忠
Based on the success of the filtration indoor an d outdoor experiment on some chemosterilants, the chemosterilant which developed by the study group and proved having best sterile effect against Anoplophora glabripennis and Tetranychus viennensis, called CSⅡ (wettable powder), we re adopted on the mensuration about the toxicity and sterilizing activity of rats, in order to know the safety about human being. The toxicity including expedit ious toxicity, the influence on sperms and bone marrow derived cells. The result s showed that the expeditious toxicity of CSⅡ is middling; it has no injury on the bone marrow derived cells of rats, but has some actions of deformation on the sperms, so it has sterilizing activity on rats. It is concluded that this chem osterilant can be adopted in trees which are utilized in no edible purpose.
Irradiation of Anopheles stephensi Liston male pupae with 8 krad induced 97.2 percent male sterility. Higher irradiation of 12 krad resulted in ca. 2 percent increase of sterility (99.1 percent) with reduced fitness of males for mating and survival. Four krad irradiation of females resulted in inhibited egg production and at 7 krad there was complete failure of females to lay eggs. Thiotepa was not effective in the sterilization of mosquitoes at the pupal stage. Dipping mosquito pupae in 1 percent P, P-bis (1-aziridinyl)-N-methylphosphinothioic amide for 2 h induced 100 percent sterility in both sexes. Chemosterilized males were permanently sterile and comparable in quality (mating competitiveness, mating ability, and survival) with untreated males
姜静; 杨忠岐; 唐艳龙; 唐桦; 高纯; 王小艺; 孟庆伟; 刘松君
为筛选出防治栗山天牛Massicus raddei (Blessig)成虫的不育剂,本研究利用灭幼脲Ⅲ号、除虫脲和杀铃脲3种仿生制剂分别稀释500倍、1000倍、1500倍、2000倍、3000倍和4000倍等6种浓度进行处理,对其成虫进行了不育性试验.结果表明,这3种不育剂不同处理在雌雄虫寿命、产卵量和产卵期、子代卵的孵化历期的差异均不显著,但经不育剂处理过的雌虫后期产卵量要明显小于对照；不同处理间子代卵的孵化率差异显著,特别是3种药剂500倍液处理后的孵化率分别为19.07％、23.74％和26.3％,远低于对照组的90.21％.三种不育剂1500倍以上的稀释浓度对卵的孵化均有明显的抑制作用,孵化抑制率与浓度之间呈正相关关系,其毒力方程均达到了极显著水平,其中来幼脲Ⅲ号比其它两种不育剂效果更好.%For selecting a bionical chemosterilant to control adults of the oak longhom beetle, Massicus raddei (Coleoptera: Cerambycidae) , a study on sterilized impacts of three bionical chemosterilants, i. e. , chlorbenzuron, diflubenzuron and triflumuron, were carried out. They were diluted to six different concentrations, i.e. , 500, 1000, 1500, 2000, 3000 and 4000 times as six treatments. The results showed that there were no significant differences among the three chemosterilants in female and male adult life - span, number of eggs - laying, the lasting time both of egg - laying and egg hatching. However, the egg numbers laid were much lower than the control group. Meanwhile, the egg - hatching rate indicated significantly different among the different treatments, and particularly the treatments of three chemosterilants with 500 - times dilution showed good results; the egg - hatching rates were 19. 07% , 23. 74% and 26. 3% respectively, comparing with the control group 90. 21%. The concentrations of three chemosterilants with 1500 -times dilution all revealed significant inhibitive impacts on egg
Andrews, R. V.; Belknap, R. W.
A single application of the male chemosterilant, alpha-chlorhydrin, to a problem sewer rat infestation resulted in reductions of rat numbers and distribution which was comparable to effects of warfarin baiting methods. Rat numbers were reduced by more than 85% by both methods. More rapid mortality and recruitment were evident for warfarin effects; the alpha-chlorhydrin treated population had a longer lag phase of growth so that reinfestation of sewer habitat to pre-treatment numbers, and dist...
Rodriguez, Stacy D.; Brar, Ramaninder K; Drake, Lisa L.; Drumm, Hannah E; Price, David P.; Hammond, John I; Urquidi, Jacob; Hansen, Immo A.
Background Sterile Insect Technique (SIT) has been successfully implemented to control, and in some cases, eradicate, dipteran insect populations. SIT has great potential as a mosquito control method. Different sterilization methods have been used on mosquitoes ranging from chemosterilization to genetically modified sterile male mosquito strains; however, sterilization with ionizing radiation is the method of choice for effective sterilization of male insects for most species. The lack of gen...
Reinbold, James B; Coetzee, Johann F; Hollis, Larry C; Nickell, Jason S; Riegel, Casey; Olson, K C; Ganta, Roman R
Chemosterilization is reported in cattle fed chlortetracycline hydrochloride (CTC) at dosages ranging from 1.1mg/kg for 120 days to 11 mg/kg for 30-60 days. The relationship between plasma CTC drug concentration and carrier clearance has not been described. Chronic carrier status was established in 21 steers with a Virginia isolate of Anaplasma marginale and confirmed by cELISA and an A. marginale-specific RT-PCR. Four negative, splenectomized steers served as active disease transmission sentinels. Steers were randomized to receive 4.4 mg/kg/day (LD); 11 mg/kg/day (MD); or 22 mg/kg/day (HD) of oral chlortetracycline; or placebo (CONTROL) for 80 days. The LD, MD and HD treatment groups consisted of 5 infected steers and 1 splenectomized steer; CONTROL group had six infected steers and 1 splenectomized steer. The daily treatments and ration were divided equally and fed twice daily. Blood samples were collected semi-weekly for determining plasma drug concentration by ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry method and assessment of disease status by both cELISA and RT-PCR. Mean (CV%) chlortetracycline plasma drug concentrations in the LD, MD, and HD groups were 85.3 (28%), 214.5 (32%) and 518.9 (40%)ng/mL during days 4 through 53 of treatment. A negative RT-PCR assay result was confirmed in all CTC-treated groups within 49 days of treatment; however, cELISA required an additional 49 to 88 days before similar results. Subinoculation of splenectomized steers confirmed chemosterilization. These results are important for influencing future chemosterilization strategies and impacting free trade policy among countries and regions of contrasting endemicity.
The advances in the application of sterilizing techniques against pest rodents in China are introduced in the paper. The development of chemosterilants, improvements of botanic sterilants, production of new steroid hormone sterilants, introduction of immunosterility and excellent properties of the sterilants are outlined. The "Space Occupation Theory" of sterile techniques is advanced after practice. The botanic sterilants with gossypol and trichosanthin as its main agents were screened and successfully applied in the large area control in the northern forest area of China. The safety of sterilants to non-target animals such as rats, rabbits, dogs, monkeys and chickens was summarized.
Zhou, Fangyuan; Zhu, Guodong; Zhao, Haipeng; Wang, Zheng; Xue, Ming; Li, Xianxian; Xu, Huaqiang; Ma, Xiaodan; Liu, Yanyan
The onion maggot, Delia antiqua, is a devastating pest of liliaceous crops and current control measures fail to avert pesticide residues, threats to agroecosystem, and costly expenditures. Insect growth regulators (IGRs) are used as trypetid pest chemosterilants for their suppression on adult fertility and fecundity, but their effects on onion flies are unknown. Here, three IGRs (lufenuron, cyromazine, pyriproxyfen) were incorporated into baits to evaluate their effects on onion fly survival, fecundity, fertility, susceptibility of adults in different ages and offspring development. Lufenuron and cyromazine did not affect survival of new-emerged adults, but lufenuron inhibited adult fertility without affecting fecundity, and cyromazine reduced fertility and fecundity. Differently, pyriproxyfen enhanced fecundity within 10 days after treatment, while it reduced adult survival without affecting fertility. The fertility of younger adults was affected by lufenuron and cyromazine whereas the fecundity was affected with cyromazine and pyriproxyfen. For offspring of onion flies treated with lufenuron or cyromazine, most of larvae died within 5 days after hatch, but surviving larvae pupated and emerged normally. Pyriproxyfen did not affect offspring larval survival or pupation but affected pupal emergence. Thus, lufenuron and cyromazine could be potential chemosterilants for onion flies. PMID:27619006
Gato, René; Companioni, Ariamys; Bruzón, Rosa Y; Menéndez, Zulema; González, Aileen; Rodríguez, Misladys
Successful SIT trials against mosquitoes in the 1960-70s were achieved by sterilizing male mosquitoes using chemosterilants. Their use was discontinued after concerns were raised about the effect of residues on non-target organisms, although scant evidence has been published. Irradiation is an expensive process; chemosterilization could be an affordable option for implementing SIT programs in developing countries. We compare life table parameters of three Aedes aegypti populations comprising different ratios of thiotepa-treated and non-treated males in order to identify the impact on reproductive potential of the presence of sterile males. No difference was observed in the survival of the treated and untreated males. The release of thiotepa sterilized males into caged Ae. aegypti populations had no effect on death or survival probability of the individuals in the cages but the fecundity of females was significantly reduced, as evaluated by hatch rate and stable age structure parameters. The significant decreases in net reproduction rate, finite rate of natural increase and intrinsic rate of natural increase in populations including sterile males are sufficient to indicate that such populations would not be able to proliferate in natural conditions. This suggests that release of Ae. aegypti thiotepa-treated males could be effective in reducing the reproductive capability of the target population and consequently contribute to vector control. PMID:24513037
The revised manual, which incorporates changes particularly regarding applied aspects, consists of 7 parts. Part 1 is divided into separate chapters on the properties of radionuclides and radiations; radiation detection and assay of radioactivity; radiation protection; tracer methodology; 15N determination; and neutron moderation and γ-ray attentuation techniques. Part 2 is concerned with radiobiology. References and a bibliography are supplied with each part. Part 3 contains 17 mental exercises, part 4 laboratory exercises on a GM counter; a scintillation counter; contamination and decontamination; and exercises on basic utilization principles. Part 5 considers radioisotope uptake and excretion paths through the insect organism; principles of internal and external tagging; with emphasis on insect physiology and ecology; various experiments on insects, and insect sterilization using 60Co and chemosterilants. Eight Appendices and a Glossary of some basic terms and concepts constitute parts 6 and 7, respectively
Hanson, Lee H.; Manion, Patrick J.
The sterility method of pest control could be an effective tool in the sea lamprey (Petromyzon marinus) control program in the Great Lakes. Some of the requirements for its successful application have been met. A field study demonstrated that the release of male sea lampreys, sterilized by the injection of 100 mg/kg of P,P-bis(1-aziridinyl)-N-methylphosphinothioic amide (bisazir), will reduce the number of viable larvae produced. The actual reduction in reproductive success that occurred was directly related to the ratio of sterile to normal males in the population. The technique can be used in many ways in an integrated control program and has considerable potential for the more effective control of the sea lamprey. Eradication is a distinct possibility.Key words: sea lamprey, Petromyzon marinus; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
Proceedings of a Symposium jointly organized by the IAEA and the Food and Agriculture Organization of the United Nations and held in Vienna, 4-8 December 1967. The meeting was attended by 82 participants from 29 countries and six international organizations. Contents: Isotope applications - ecology (7 papers); Radiation effect studies - non-genetic (8 papers); Isotope applications - physiology and biochemistry (2 papers); Isotope applications - chemosterilants (2 papers); Sterile-male technique (9 papers); Radiation effect studies - genetic (5 papers); Isotope applications - genetic (1 paper). Each paper is in its original language (21 English, 11 French, 1 Russian and 1 Spanish) and is preceded by an abstract in English with a second one in the original language if this is not English. Discussions are in English. (author)
Isotopes are commonly used in agricultural research in developed countries, but because of a lack of both training and equipment isotopic techniques are not frequently used in developing countries. This manual has been prepared with the aim of helping entomologists and others responsible for the control of insects in developing countries become familiar with the potential uses of isotopes and radiation in solving some of their research and insect control problems. After chapters dealing with radiation safety, the general properties of radiation and isotopes (especially those used by entomologists), and radiation detection and assay of radioactivity, two further chapters discuss applications to entomological problems and the sterile insect technique. Numerous case studies are described, and the final chapter also includes a description of eight laboratory exercises to investigate the effects of gamma irradiation and chemosterilants on insects. Refs, figs and tabs
Following the successful eradication of the screwworm, Cochliomyia hominivorax (Coql.), from the island of Curacao and the southeastern United States of America the sterile insect technique (SIT) was tested against several other noxious insects, including the tsetse fly. Between 1967 and 1987, experiments were conducted in Zimbabwe and the United Republic of Tanzania (East Africa) and in Burkina Faso and Nigeria (West Africa) to test the feasibility of the new technique in eradicating selected species of tsetse fly. For the Zimbabwe programme, sterile flies were obtained from field collected pupae treated with the chemosterilant tepaR. Complete eradication was not achieved, primarily because of insufficient sterile males emerging from the wild pupae. In later programmes in the United Republic of Tanzania, Burkina Faso and Nigeria, flies were obtained from laboratory bred mass reared colonies. Males were sterilized either as pupae (Tanzanian project) or as young adults using gamma irradiation from a 60Co or 137Cs source. Efforts currently in progress to apply the technique to eradicate Glossina austeni from Zanzibar Island, United Republic of Tanzania, have attracted considerable interest and funding from several international organizations. Past and current tsetse SIT programmes are reviewed and future prospects of the technique in large scale tsetse/trypanosomiasis programmes are discussed. (author). 10 refs
Magris, Martina; Wignall, Anne E; Herberstein, Marie E
The sterile male technique is a common method to assign paternity, widely adopted due to its relative simplicity and low cost. Male sterility is induced by exposure to sub lethal doses of chemosterilants or irradiation, the dosage of which has to be calibrated for every species to provide successful male sterilisation, without affecting male physiology and behaviour. While the physiological effects of sterilisation are usually assessed for each study, the behavioural ones are rarely analysed in detail. Using the orb web spider Argiope keyserlingi as a model we first tested (1) the validity of the thread assay, which simulates male courtship behaviour in a standardised context, as a proxy representing courtship on a female web. We then investigated (2) the effectiveness of male sterilisation via irradiation and (3) its consequences on male courtship behaviour. Our results validate the thread assay and the sterile male technique as legitimate tools for the study of male courtship behaviour and fertilisation success. We show that these techniques are time and cost effective and reduce undesirable variation, thereby creating opportunities to study and understand the mechanisms underlying sexual selection. PMID:25794431
Le, Binh V.; Nguyen, Jennifer B.; Logarajah, Shankar; Wang, Bo; Marcus, Jacob; Williams, Hazel P.; Catteruccia, Flaminia; Baxter, Richard H. G.
Male Anopheles mosquitoes coagulate their seminal fluids via cross-linking of a substrate, called Plugin, by the seminal transglutaminase AgTG3. Formation of the “mating plug” by cross-linking Plugin is necessary for efficient sperm storage by females. AgTG3 has a similar degree of sequence identity (∼30%) to both human Factor XIII (FXIII) and tissue transglutaminase 2 (hTG2). Here we report the solution structure and in vitro activity for the cross-linking reaction of AgTG3 and Plugin. AgTG3 is a dimer in solution and exhibits Ca2+-dependent nonproteolytic activation analogous to cytoplasmic FXIII. The C-terminal domain of Plugin is predominantly α-helical with extended tertiary structure and oligomerizes in solution. The specific activity of AgTG3 was measured as 4.25 × 10−2 units mg−1. AgTG3 is less active than hTG2 assayed using the general substrate TVQQEL but has 8–10× higher relative activity when Plugin is the substrate. Mass spectrometric analysis of cross-linked Plugin detects specific peptides including a predicted consensus motif for cross-linking by AgTG3. These results support the development of AgTG3 inhibitors as specific and effective chemosterilants for A. gambiae. PMID:23288850
The Grosch effect (i.e., of radiation interfering with utilization of nutrients in insects) became applicable to pest control when Galun and Warburg discovered that irradiated ticks fed once would seldom if ever feed again. This lifelong sensation of 'impletion' does not interfere with sexual competitiveness, but it does render harmless a pest that is a pest during the adult stage of its life cycle. It would seem that the general principle of treating adult pests to limit their feeding capacity could be extended to other pests. When insect pests are- living in stored food products, it is a general rule that desirably low levels of radiation can be used to eradicate the pest if sterilizing doses rather than insecticidal doses are used. With the entire population of both males and females being irradiated, the sterilizing dose is often much lower than that which would be desirable when the insects are mass-reared for irradiation and release. Where mass-rearing techniques are not feasible, or where the pestiferousness of adults cannot be overcome by radiation or other treatments, field-irradiation facilities in baited traps can be devised. These have some advantages over similar traps containing chemosterilants. Wherever it can be used, the method of mass-rearing, irradiation, and release is still the most desirable way to control insect pests. (author)
The contamination of raw materials with microorganisms is a potential hazard to human health, especially if these materials are kept for a certain time under conditions that enhance microbial multiplication. Since the goods in question are by no means cheap bulk materials, but are highly ranked substances, the method of germ reduction by heat treatment is not suitable, and various so-called cold sterilizations have to be used (chemical, irradiation). The article examines the value of these, and in particular how they are assessed. Until the sixties, it was mainly the microbicidal effect of these treatments that was judged; today, the emphasis is on the assessment of the secondary reactions of the agents with the treated commodity and in particular their residual toxicity. In the case of chemical treatments, toxicity is determined directly by application of overdoses. It should be stressed that this is not comparable with the indirect assessment of the toxicity of gamma irradiation, by feeding irradiated goods. Of the available chemosterilants, formaldehyde has great disadvantages in spite of its high volatility, because of its high protein factor and its delayed vaporization from surfaces, due to polymerization. Propylene oxide is less active, requiring higher concentrations, which in turn results in increased residues. Therefore, the agent of choice is still ethylene oxide, since it diffuses quickly and is highly reactive; selection of genetically resistant microorganisms is therefore not possible, as opposed to the case of gamma radiation
The first laboratory and field experiments on genetic control were with tsetse flies, and they made use of the sterility in crosses and hybrids between closely related species of the Glossina morsitans complex. Backcrosses indicate that there are two separate sterility mechanisms involved: (a) genetic incompatibility between a mother and the products of alien genes in the embryo or larva in the uterus; (b) inability of hybrid males to inseminate due to incompatibility of their X-chromosomes with an alien Y or autosomes. The two largest sterile male release programmes have been in Tanzania and Upper Volta, and have used irradiation at the pupal or adult stage, respectively, for the production of sterility. Male tsetse are remarkably resistant to radiosterilization and, with the doses required to induce dominant lethals in more than 95% of sperms, premature senescence and lethargic behaviour of the males tends to result. With G. morsitans irradiated at the puparial stage these effects can be alleviated by the use of a nitrogen atmosphere during irradiation. If the puparia are then transferred to air at 110C for transport to the release site, immediate emergence occurs on re-warming after arrival. This advantageous procedure was used for the releases in Tanzania. In addition to dominant lethals, irradiation also produces chromosome translocations which cause inherited partial sterility. A homozygous translocation line was selected but this example did not have sufficient fitness to be used in a mass rearing programme. Chemosterilants can be applied by pupal dipping, adult contact with deposits or in aerosols. Studies are now in progress on their use in association with odour-baited traps or pheromone-baited decoys as a means of sterilizing the wild population and thus avoiding the costly and difficult process of mass rearing tsetse. (author)
Integration of the sterile insect technique (SIT) and autosterilisation lethality in the eradication of Glossina fuscipes fuscipes Newst. (Diptera, Glossinidae) in Buvuma Islands in Lake Victoria, Uganda
The years of 1970s to 1990s saw the development of bait technology for the control of tsetse flies from their infancy to their optimum levels. The technology relies on attracting the flies to trapping and killing devices, relying on olfactory and visual cues to artificial and natural objects which the flies probably perceive as their hosts. Despite the present level of improvement, the catching or trapping efficiency is low, averaging 20-35%, and some tsetse species hardly respond to these techniques. This makes sustaining control programmes to a level where economic development can proceed effectively elusive, leading to the re-invasion and collapse of many tsetse control projects. Efforts are therefore being made to incorporate different killing methods into the trapping systems. Lethal insect techniques (LIT) with pathogens, insect growth regulators and other chemosterilants are incorporated into bait technology to amplify their effectiveness as the flies can transfer them to other members of the species which cannot get access to the attractive devices. They are compatible with the sterile insect technique. Prospects for autosterilisation of the tsetse flies have been reviewed by Langley and Coates (1982) who also assessed the incorporation of sex pheromones and bisazir in the field. Encouraging field results were obtained with Pyroprxyfen (Sumitomo Chemical Co.) which is a juvenile hormone mimic that allows the larvae of G. morsitans morsitans to be produced normally but on pupation, further development was arrested after twenty days of the thirty day intrapupal period, 'effectively' making the females sterile (Hargrove and Langley 1990). However, when triflumuron is applied at doses of 0.5 micrograms per tsetse fly the following reproductive cycle was arrested with no recovery over four reproductive cycles (forty five days). Birth products of the sterilised flies ranged from abortion of eggs to fully grown larvae which formed non-viable puparia. The aim of
The work of blood collecting nurses is special, and it is often exposed to the occupational hazardous factors of physics, chemistry and biology and psychology in the course of work, which can not only affect the nursing quality, but also seriously affect the mental and physical health and quality of life of nurses, therefore, we should improve the occupational protection awareness and overall quality of blood collecting nurses, enhance the aseptic concept, enhance the hand hygiene disinfection management, do a good job in the treatment and protection of sharp instrument and pricking wound , enhance the protection of disinfection chemosterilant, try to avoid being exposed to occupational hazardous factors and its effect on physical health, enhance self-protection awareness, avoid iatrogenic infection, build a safe and health work environment and standard effective prevention process and provide a better nursing service for patients.%采血护士的工作较为特殊，在工作过程中常暴露在物理、化学和生物和心理等职业危害因素中，这不仅影响护理质量，并且还严重影响护士的身心健康和生活质量。所以，要提高职业防护意识和采血护士的整体素质，增强无菌观念，加强手卫生消毒管理，做好锐器和针刺伤的处理及防护，加强化学消毒灭菌剂的防护，尽量避免门诊采血护士接触职业危害因素及其对身体健康造成的影响，增强自我保护意识，避免医源性感染，为其创造一个安全健康的工作环境和标准有效的预防流程，为病人提供更优质的护理服务。
Full text: The paper deals with the study on the induction of male sterility in Exorista sorbillans (Diptera: Tachinidae), which is a serious pest of the popular mulberry silkworm, Bombyx mori (Lepidoptera: Bombycidae). The endoparasitoid inflicts considerable damage to the silk industry by large-scale parasitisation of the silkworm, leading to heavy losses ranging from 30-70%. The pest, which was unknown till a few decades ago in peninsular India, has firmly established itself due to its reproduction and locomotor activities. Induction of male sterility through chemosterilants has been attempted to limit the reproductive porential of the fly population. The present study deals with induction of male sterility through gamma radiation. The uzi maggots were treated with different doses of gamma radiation and their effects on maggot, pupal and adult mortality, longevity, fecundity and cytology of uzifly were investigated in detail. The results show that the dosage of 11 Gy is relatively more effective in the induction of male sterility on large scale. When the untreated female was crossed with the irradiated male, the number of eggs laid was normal indicating no reduction of fecundity. However, none of the eggs hatched, probably due to the fact that the exposed maggots contain germ cells that were irradiated before gametogenesis. This resulted in a complete nuclear change in a germ cell, which prevents it from maturing or participating in zygote formation. In addition, it was found that the irradiation had an effect on the size and shape of the testis. By releasing these irradiated sterile flies, which have a high survival and vigour, we can ensure the reduction of the natural population. The cytological basis of induced male sterility has been studied through chromosome preparation of testis and ovaries of irradiated pupae. Chromosomal aberrations like deletions and fragmentations were observed. The ultrastructural variation in irradiated spermatids and abnormalities
occur and must be dealt with in Florida and California, Mexico and Chile. Fruit flies, like any other pest, have been attacked with biocides at the farm level. Citrus is an instructive example. Citrus flowers and fruits twice a year, and various species and varieties provide year-round harvests. Biocides are typically applied to citrus every 10-15 days. Even so, the effectiveness is usually only 70-80%, due to uncontrolled neighboring farms, untreated hosts, problems with the spraying equipment, dose miscalculations, etc. Aerial applications of bait sprays to wider areas are more expensive, require a regional plan, and can represent a major impact to the environment. All means of application can leave pesticide residues in the fruit. Trade in fresh fruits and vegetables is being liberalized on a world-wide basis as part of globalization. At the same time, local consumption of fresh products is increasing in the search for a healthier life. Pesticides are increasingly less acceptable in both the export trade and local markets. Newly adopted food safety and phytosanitary standards require the establishment of either low prevalence or entirely fruit fly-free areas. Environmental considerations reinforce the already favorable cost-benefit picture for the Sterile Insect Technique (SIT) as an alternative to controls that use chemicals alone. The SIT has been in use since the 1950s. The aim of the technique is to disrupt the life cycle of the fly, mating the wild population with sterile flies reared at a 'fly factory'. Sterilization is accomplished by exposing insects to a specific dose of gamma radiation emitted by radioisotopes (cobalt-60 or cesium-137). Irradiation is a central and indispensable part of the total SIT process: every insect among millions produced each week must to be sterilized. No other method is available to achieve sterilization; chemosterilants, linear accelerators and the like have proven less cost-effective
-appearance of An. funestus which was resistant to pyrethroids, but not to DDT. This resulted in a switch back to DDT in 2000. g) Latin America. As the intensity of the national DDT campaigns has waned, malaria cases have increased and this has been associated with an increase in the colonization of the Brazilian Amazon. Multiple insecticide resistance in An. albimanus in Central America in the 1970s was due to pressure from agricultural insecticides; with introduction of IPM and partial abandonment of cotton growing; however, this resistance has now declined. In 1970s there were successful field trials of SIT using chemosterilization against An. albimanus in El Salvador where genetic sexing based on Y translocation of insecticide resistance gene was used. An. aegypti was eradicated from most of the Americas (but not USA) in the 1950s as a measure to control yellow fever but there has been subsequent re-infestation resulting in dengue epidemics. Effective control has only been maintained in Cuba.