Inter-regional mating compatibility among Bactrocera dorsalis populations in Thailand (Diptera,Tephritidae)

Mating compatibility among recently colonized (wildish) populations of Bactrocera dorsalis (Hendel) from different geographic origins in Thailand was assessed through inter-regional mating tests. Outdoor octagonal nylon screen field cages containing single potted mango trees (Mangifera indica L.) were used. Sexual compatibility was determined using the index of sexual isolation (ISI), the male relative performance index (MRPI), and the female relative performance index (FRPI). The ISI values indicated that the northern population of Bactrocera dorsalis from Chiang Mai province was sexually compatible with the southern population of Bactrocera dorsalis (previously Bactrocera papayae) from Nakhon Si Thammarat province. The MRPI values showed that the northern males had a slightly higher tendency to mate than southern males, while the FRPI data reflected that females of both origins participated equally in matings. In all combinations there were no differences between homotypic and heterotypic couples in mating latency. Southern males tended to mate first with southern females, followed by northern males mating with northern females, while the latest matings involved heterotypic couples, in particular northern males mating with southern females. Overall, more couples were collected from higher parts of the field cage and the upper tree canopy, while there were no differences between the origins of flies in terms of elevation of couples within the cage. Laboratory assessments of fecundity showed no differences in the average number of eggs resulting from inter-regional crosses. Development of immature stages was also equal in the two hybrid crosses, with no differences found in the number of pupae produced, percentage pupal recovery, and percent adult emergence. The practical implication of this study is that colony of Bactrocera dorsalis derived from any northern or southern region of Thailand can potentially be used in sterile insect technique programs against this pest.     

Evaluation of dyes for marking painted apple moths (Teia anartoides Walker, Lep. Lymantriidae) used in a sterile insect release program

Abstract  Two methods of marking painted apple moth ( Teia anartoides Walker, Lepidoptera: Lymantriidae), internal and external dyes, were investigated for use with the sterile insect technique, to ensure that wild and released moths could be distinguished absolutely during the eradication program. Calco Red dye was used to mark all moths internally. It was added to artificial diet and was detectable in the adults. Dye was incorporated into the larval diet at four rates. No differences were observed in mortality of the larvae, fertility of the adult female or response of male moths to virgin females in a flight tunnel. Fluorescent powder dyes were used throughout the sterile insect program to identify irradiated moths, as well as their release location and colony. However, the powdered dyes reduced the ability of male moths to detect a component of the sex pheromone in electro-antennogram tests and to respond to a calling virgin female in flight tunnel trials. Field trials suggest that moths may subsequently overcome these negative effects and respond to female moths, as moths heavily coated in dye were recaptured.     

Mate choice by wild and mass‐reared females of the Mediterranean fruit fly

The sterile insect technique (SIT) is used to control Mediterranean fruit fly, Ceratitis capitata (Wiedemann), but its effectiveness is limited by low sexual competitiveness of mass‐reared males. This study investigated whether wild and mass‐reared [from a temperature sensitive lethal (tsl) genetic sexing strain] females display similar mate preferences and thus exert similar selective forces on the evolution of male courtship behaviour. Wild females preferred wild males over tsl males, whereas tsl females mated indiscriminately. The probability that mounting resulted in copulation was related to the duration of pre‐mount courtship for wild females, and wild males performed longer courtships than tsl males. Copulation occurred independently of courtship duration in tsl females. Counter to the aim of the SIT, female choice by tsl females appears to promote the evolution of male behaviour disfavoured by wild females.     

The effect of mass‐rearing on death‐feigning behaviour in the sweet potato weevil (Coleoptera: Brentidae)

The aim of our study was to examine the effect of mass‐rearing, in which there is no exposure to predators, on antipredator traits of insects for improving sterile insect technique programs. The duration of death‐feigning (antipredator behaviour) in sweet potato weevil Cylas formicarius (Summers) (Coleoptera: Brentidae) after mass‐rearing for 71 generations were compared with those in wild strain. There was no significant difference in the duration of death‐feigning between wild and mass‐reared strains. This indicated that the death‐feigning behaviour of mass‐reared strain was maintained for 71 generations even in the absence of predators. We discuss the reasons why death‐feigning behaviour is maintained after mass‐rearing.     

Compatibility of codling moths Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) from South Africa with codling moths shipped from Canada

The sterile insect technique (SIT) has been successfully applied against codling moth Cydia pomonella (Linnaeus) (Lepidoptera; Tortricidae) in British Columbia since 1992 where the mass‐rearing facility produces between 15 and 16 million moths per week. Due to the seasonality of this pest, the facility is only fully utilized for part of the year. The time and expense of implementing SIT against codling moth in South Africa may be substantially reduced if moths from Canada were sexually compatible with those from South Africa. In addition, because the pome fruit‐growing season in both countries is opposite, the programme in Canada might benefit by maintaining moth production year‐round and selling moths to South Africa. Semi‐field studies in small cages and release‐recapture studies were conducted in an unsprayed apple orchard in South Africa to assess mating compatibility of laboratory‐reared codling moth from Canada and wild codling moths from South Africa. The results suggest that Canadian codling moth males were equally attracted to calling Canadian and South African females despite the fact that Canadian moths had been transported (from Canada to South Africa) for 48 h as both pupae and adults. The data also suggest that at lower field temperatures Canadian moths were more active than South African moths. Results from the release‐recapture field trials indicated that Canadian and South African males were equally attracted to Canadian and South African females. These results suggest that codling moths from Canada and South Africa are fully compatible and indicate that Canadian moths can be used for SIT studies in South Africa. As these studies were conducted with moths from two very different climatic and time zones, it is proposed that populations of codling moth in other pome fruit production areas may also be compatible with the Canadian moths.     

Does isometamidium chloride treatment protect tsetse flies from trypanosome infections during SIT campaigns?

African animal trypanosomosis is a major pathological constraint to cattle breeding across 10 million km2 of sub-Saharan West African countries infested by tsetse flies, their cyclic vectors. The release of sterile males (sterile insect technique [SIT]) is a potentially important control technique aimed at eliminating the vectors. Prior to release, tsetse are generally treated with isometamidium chloride, a trypanocide, to prevent them from transmitting parasites. The present study investigated the preventive action of isometamidium chloride (0.5 mg/L) on the subsequent susceptibility of tsetse released into the wild. A total of 1755 Glossina palpalis gambiensis Vanderplank and 744 Glossina tachinoides Westwood were released, of which 50 and 48, respectively, were recaptured 22-43 days after release. Their probosces were analysed by polymerase chain reaction to identify mature infections with three trypanosome species (Trypanosoma vivax, Trypanosoma brucei sensu lato and Trypanosoma congolense savannah type). Two mature infections with T. vivax and four with T. congolense were detected, indicating that the use of this treatment regimen in an SIT campaign would not totally prevent sterile males from transmitting trypanosomes.     

Efficacy of Tower Medfly Eclosion Systems

A 16-repetition experiment was conducted to evaluate the performance of the “tower” system for eclosion of sterile medflies, Ceratitis capitata (Wiedemann). This system has now replaced the PARC system previously used in Florida S.I.T. programs. In addition to testing the efficacy of these eclosion systems, as compared to the PARC system, quality control was also monitored and evaluated. No significant differences were found between either system in regards to C. capitata yield, weight or flight ability (p=0.05). Based on these comparative trials, the tower eclosion system appears to be an efficient alternative to the PARC system.     

Large indoor cage study of the suppression of stable Aedes aegypti populations by the release of thiotepa-sterilised males

The sterile insect technique (SIT) is a promising pest control method in terms of efficacy and environmental compatibility. In this study, we determined the efficacy of thiotepa-sterilised males in reducing the target Aedes aegypti populations. Treated male pupae were released weekly into large laboratory cages at a constant ratio of either 5:1 or 2:1 sterile-to-fertile males. A two-to-one release ratio reduced the hatch rate of eggs laid in the cage by approximately a third and reduced the adult catch rate by approximately a quarter, but a 5:1 release drove the population to elimination after 15 weeks of release. These results indicate that thiotepa exposure is an effective means of sterilising Ae. aegypti and males thus treated are able to reduce the reproductive capacity of a stable population under laboratory conditions. Further testing of the method in semi-field enclosures is required to evaluate the mating competitiveness of sterile males when exposed to natural environmental conditions. If proven effective, SIT using thiotepa-sterilised males may be incorporated into an integrated programme of vector control to combat dengue in Cuba.     

苹果蠹蛾的综合防控和遗传控制研究进展

苹果蠹蛾是仁果类水果的重要检疫害虫,在世界各地造成了巨大的经济损失。目前对其化学防治、化学生态调控、病毒等防治方法研究较多,但仍不能满足防控该害虫的需要,对新型防控技术的需求日益增强。不育昆虫释放技术(SIT)是一种可控制甚至根除靶标害虫的环境友好型防控技术,但传统SIT技术存在一定的局限性,如较难区分性别与筛选雌雄虫、辐射不育昆虫的交配竞争力和适合度降低等问题,这些缺陷随着昆虫遗传修饰技术的发展将得以解决,并将在害虫防控进程中起到积极作用。本文综述了苹果蠹蛾主要防控技术研究现状,介绍了通过遗传修饰技术改善SIT的技术策略,并综合分析了我国开展苹果蠹蛾遗传修饰研究情况和将其应用在苹果蠹蛾防控体系中的可行性及优势。     

Effects of irradiation dose rate on quality and sterility of Queensland fruit flies, Bactrocera tryoni (Froggatt)

Queensland fruit fly (Bactrocera tryoni; Q‐fly) pupae are routinely irradiated to induce reproductive sterility in adults released in a sterile insect technique programme. Although there have been some studies of how total dose influences fly quality, dose rate has not been considered. In the present study, pupae were irradiated at a target dose range of 70–75 Gy at dose rates of approximately 5, 7, 26, 57 and 80 Gy/min and were then subjected to routine IAEA/FAO/USDA quality control tests including emergence, flight ability, mortality under stress and sterility induction. No significant effects of dose rate were found on emergence or flight ability. Sterility induction was also found to be independent of dose rate, a result conforming to a ‘one‐hit’ ionizing event hypothesis. Flies irradiated at higher dose rates suffered increased mortality under stress. This appears to stem from an increased tendency to over‐shoot the target dose when irradiating at high dose rates. We recommend that, to reduce potential error in total target dose, the lowest practical dose rate be used when irradiating Q‐fly pupae for use in the sterile insect technique.