Age-dependent variation in mating success of sterile male Mediterranean fruit flies (Diptera: Tephritidae): implications for sterile insect technique

The sterile insect technique (SIT) is widely used in integrated programs against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in the mating ability of the released males. To counter this deficiency, SIT programs rely upon the production and release of large numbers of sterile males to achieve high overflooding (sterile:wild male) ratios. To ensure a high release volume, emergence facilities release adult males at a young age (2 d old in some cases). The primary objective of this study was to describe age-dependent variation in the mating propensity and competitiveness of sterile males of C. capitata. Males that were 2 or 3 d old had lower mating propensity than males that were > or =4 d old, and 3-d-old males had lower mating competitiveness than males that were > or =4 d old. Given these results, we measured the effect of a longer holding period on male mortality in storage boxes. With delayed food placement, males held in storage boxes for 4 d after emergence showed no higher mortality than males held for only 2 d (the standard interval). Using large field enclosures, we compared the levels of egg sterility attained via releases of 2- versus 4-d-old sterile males at two overflooding ratios (5:1 and 100:1). At the lower ratio, the proportion of unhatched eggs observed for trials involving 2-d-old sterile males was not, on average, significantly higher than that observed for matings between wild flies (33 versus 25%, respectively), whereas the level of egg sterility observed for releases of 4 d old sterile males was 62%. At the 100:1 overflooding ratio, the proportion of unhatched eggs associated with the 2-d-old sterile males was 58%, a level not significantly different from that induced by 4-d-old sterile males at the 5:1 ratio and significantly lower than the level (79%) observed for 4-d-old sterile males at 100:1 overflooding ratio. The implications of these results for SIT are discussed.     

Sterile insect technique and Mediterranean fruit fly (Diptera: Tephritidae): assessing the utility of aromatherapy in a Hawaiian coffee field

The sterile insect technique (SIT) is widely used in integrated programs against tephritid fruit fly pests, particularly the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in the mating ability of the released males. One potential solution involves the prerelease exposure of males to particular attractants. In particular, exposure of male Mediterranean fruit flies to ginger, Zingiber officinale Roscoe, root oil (GRO) has been shown to increase mating success in laboratory and field cage trials. Here, we describe a field experiment that compares the level of egg sterility observed in two Hawaiian coffee, Coffea arabica L., plots, with GRO-exposed, sterile males released in one (treated) plot and nonexposed, sterile males released in the other (control) plot. Once per week in both plots over a 13-wk period, sterile males were released, trap captures were scored to estimate relative abundance of sterile and wild males, and coffee berries were collected and dissected in the laboratory to estimate the incidence of unhatched (sterile) eggs. Data on wild fly abundance and the natural rate of egg hatch also were collected in a remote area that received no sterile males. Despite that sterile:wild male ratios were significantly lower in the treated plot than in the control plot, the incidence of sterile eggs was significantly higher in the treated plot than in the control plot. Correspondingly, significantly higher values of Fried's competitiveness index (C) were found, on average, for treated than control sterile males. This study is the first to identify an association between the GRO "status" of sterile males and the incidence of egg sterility in the field and suggests that prerelease, GRO exposure may represent a simple and inexpensive means to increase the effectiveness of Mediterranean fruit fly SIT programs.     

Aromatherapy on a large scale: exposing entire adult holding rooms to ginger root oil increases the mating competitiveness of sterile males of the Mediterranean fruit fly in field cage trials

The sterile insect technique (SIT) is widely used in integrated programs against fruit fly pests, particularly the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in male mating competitiveness. One potential solution involves the pre-release exposure of males to specific attractants. In particular, male exposure to ginger root oil [Zingiber officinale Roscoe (Zingiberaceae); hereafter GRO] has been shown to increase mating success dramatically in field cage trials. Initial studies exposed small groups of males (25 individuals), but more recent work has demonstrated that GRO exposure involving standard storage boxes (containing ≈ 36 000 males) also results in enhanced mating performance. The objective of the present study was to determine whether aromatization of entire trailers, holding ≈ 14 million sterile males from a genetic sexing [temperature sensitive lethal (tsl)] strain, increases male mating success. Independent of the total dose, spatial distribution, or type of dispenser used, sterile males exposed to GRO for a 24-h period displayed greater mating success than non-exposed males in mating cage trials (in which tsl males competed against males from a standard, bisexual strain for females from this same standard strain). Averaged over all experiments, tsl males exposed to GRO obtained 54% of all matings compared to 38% for non-exposed tsl males, an increase of 42%. The implications of these findings for SIT programs against C. capitata are discussed.     

Sexual competitiveness of sterile Ceratitis capitata males exposed to essential oils from non-host plant species native to Argentina

The sterile insect technique (SIT) is used to control fruit fly pests, such as the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Enhancing sexual competitiveness of mass-reared sterile males can contribute to making this technique more effective. It has been shown that exposure to volatiles from essential oils (EOs), such as ginger root oil (GRO) and those from host fruits, increases male mating success. We evaluated the effect of EOs from non-host species native to Argentina, Schinus polygama (Cav.) Cabrera (Anacardiaceae) and Baccharis spartioides (Hook. & Arn.) Remy (Asteraceae), on the sexual competitiveness of sterile C. capitata males. In field cage experiments, sterile males exposed to S. polygama EO increased their mating success. In addition, sterile males exposed to this EO achieved more matings on trees than non-exposed males, thus suggesting the former are more prone to locate and defend the pheromone-calling territory. Deprivation of water and/or food significantly reduced males' life span, but exposure to S. polygama EO and GRO did not affect their survival. Schinus polygama EO is composed of mono- and sesquiterpenes with behavioral and electroantennographic responses in medflies, indicating that semiochemicals that boost medfly sexual competitiveness combine in this EO.     

Female presence enhances sexual performance of sterile Anastrepha ludens males of the Tapachula-7 GSS strain

The sterile insect technique (SIT), used for the control of many tephritid fly pests, is based on the rearing and release of large numbers of sexually competitive sterile insects into a wild population. In the interest of reducing expenses and increasing SIT effectiveness, genetic sexing strains (GSS) have been developed. These strains allow the production and release of only males. The objective of our study was to assess the effects of pre-release adult exposure to methoprene and to females on the mating propensity and mating competitiveness of GSS sterile males of Anastrepha ludens (Loew) (Diptera: Tephritidae). GSS sterile males were kept on a protein-sugar (protein-fed) or a protein-sugar-methoprene diet and were exposed to different proportions of females for the normal pre-release period of 5 days. Using laboratory and field-cage bioassays, we examined the influence of methoprene and female presence on the mating success of sterile males of 3–9 days old, in competition for wild females with untreated males and with wild males. Methoprene and female exposure had no significant effects on male mating success in the laboratory, whereas age had a positive relationship with the number of copulations observed. However, in field-cage bioassays, males exposed to females obtained a higher number of copulations than unexposed control males. Possible implications of these findings for programs that use GSS and especially for the campaign against Mexican fruit flies are discussed.     

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.     

Capture of mass‐reared vs. wild‐like males of Ceratitis capitata (Dipt., Tephritidae) in trimedlure‐baited traps

The sterile insect technique (SIT) is widely used to suppress or eradicate infestations of the Mediterranean fruit fly, Ceratitis capitata (Wied.), an insect whose broad polyphagy poses a serious threat to fruit and vegetable crops. The SIT involves the production, sterilization and release of sterile insects to obtain sterile male by wild female matings, thus yielding infertile eggs. Mass‐rearing over many generations is known to produce dramatic changes in the behaviour and life history of C. capitata. This study investigated the possibility that mass‐rearing also alters male response to trimedlure, a sex‐specific attractant widely used in detection and monitoring programmes. We compared captures of released males from a mass‐reared strain and a recently established colony of wild flies in trimedlure‐baited Jackson traps at three spatial scales – open field, large field enclosures (75 m²) and small field cages (7 m²) – in two separate years. In the first year, males were used independently of flight ability, while in the second year only males with demonstrated flight capability were used. Trap capture was scored 2 days after release for the open field and the large field enclosures but either 1 h or 1 day after release in the small field cages. The findings were consistent across these different experiments: wild‐like males were captured in significantly greater numbers than mass‐reared males in both years of study, except in the trials lasting 1 day in the small field cages where significantly more wild than mass‐reared males were captured in 1 year but not the other. These results are compared with other studies, and their implications for SIT are discussed.     

Effects of post-teneral nutrition and ginger root oil exposure on longevity and mortality in bait treatments of sterile male Ceratitis capitata

Area-wide Sterile Insect Technique (SIT) programmes against medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), are being increasingly implemented worldwide. A key issue for SIT is to release sterile males that are sufficiently competitive with males from the wild population. Post-teneral nutrition and ginger root oil (GRO) exposure of sterile males prior to release have been shown to improve male competitiveness or performance. However, few studies are available on the effect of post-teneral nutrition and ginger oil exposure on longevity and mortality in bait treatments by sterile male C. capitata . In this study, we found that longevity was increased by the addition of protein to the standard pre-release sugar diet, whereas exposure to GRO did not influence the longevity of sterile males. Mortality in spinosad baits was influenced both by diet and GRO exposure. Sterile males on a protein-deprived diet suffered greater mortality than sterile males fed with both sugar and protein. When sterile males were fed on the protein-deprived diet, GRO exposure increased their mortality. However, no significant differences were found in adults on the sugar-protein diet, whether or not they had been exposed to GRO. These results show, for the first time, a negative effect of GRO exposure in terms of increasing mortality in proteinaceous bait treatments, a common practice in areas where SIT is implemented. Nevertheless, this effect could be reduced by the addition of protein to the standard pre-release diet. The implications of these results for SIT programmes against C. capitata are discussed.     

Swarming and mating activity of Anopheles gambiae mosquitoes in semi‐field enclosures

Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) is the major Afro‐tropical vector of malaria. Novel strategies proposed for the elimination and eradication of this mosquito vector are based on the use of genetic approaches, such as the sterile insect technique (SIT). These approaches rely on the ability of released males to mate with wild females, and depend on the application of effective protocols to assess the swarming and mating behaviours of laboratory‐reared insects prior to their release. The present study evaluated whether large semi‐field enclosures can be utilized to study the ability of males from a laboratory colony to respond to natural environmental stimuli and initiate normal mating behaviour. Laboratory‐reared males exhibited spatiotemporally consistent swarming behaviour within the study enclosures. Swarm initiation, peak and termination time closely tracked sunset. Comparable insemination rates were observed in females captured in copula in the semi‐field cages relative to females in small laboratory cages. Oviposition rates after blood feeding were also similar to those observed in laboratory settings. The data suggest that outdoor enclosures are suitable for studying swarming and mating in laboratory‐bred males in field‐like settings, providing an important reference for future studies aimed at assessing the comparative mating ability of strains for SIT and other vector control strategies.     

Comparative rearing parameters for bisexual and genetic sexing strains of Zeugodacus cucurbitae and Bactrocera dorsalis (Diptera: Tephritidae) on an artificial diet

The Sterile Insect Technique (SIT) is an important component of area wide programs to control invading or established populations of pestiferous tephritids. The SIT involves the production, sterilization, and release of large numbers of the target species, with the goal of obtaining sterile male x wild female matings, which yield infertile eggs. A major advance in SIT involved sex-linked, genetic manipulations that allowed the production and release of male-only strains (also termed genetic sexing strains, GSS). The use of GSS avoids matings between sterile males and females, which may divert males from seeking and mating with wild females, and studies show that male-only releases result in greater suppression of wild populations than standard bisexual releases (i.e., those including both males and females). GSS based on sex-linked pupal color exist for Zeugodacus cucurbitae (Coquillett) and Bactrocera dorsalis (Hendel), two important agricultural pest species, but their rearing characteristics have not been documented in detail. The goal of the present study was to compare the pupal color sexing and bisexual strains for each of these species with respect to important rearing parameters, including egg production and eclosion of larvae from eggs (egg hatch), pupal recovery, and weight, emergence rate, and flight ability. In both species, most of these parameters were significantly greater for the bisexual strain than the GSS, and, for a given number of eggs, the production of flight-capable adults was approximately 2 times greater in the bisexual strains of both species. The potential usefulness of GSS in SIT against Z. cucurbitae and B. dorsalis is assessed based on these findings.     

Management and eradication options for Queensland fruit fly

Several tephritid fruit flies have explosive population growth and a wide host range, resulting in some of the largest impacts on horticultural crops, reducing marketable produce, and limiting market access. For these pests, early detection and eradication are routinely implemented in vulnerable areas. However, social and consumer concerns can limit the types of population management tools available for fruit fly incursion responses. Deterministic population models were used to compare eradication tools used at typical densities alone and in combination against the Queensland fruit fly (‘Qfly’), Bactrocera tryoni. The models suggested that tools that prevent egg laying are likely to be most effective at reducing populations. Tools that induced mortality once Qfly was sexually mature only slowed population growth, as successful mating still occurred. Release of sterile Qfly when using the sterile insect technique (SIT) interferes with the successful mating of wild flies, and of the tools investigated here, SIT caused the greatest reduction in the population at the prescribed release rate. Used in tandem with SIT, protein baits slightly improved the rate of population reduction, but the male annihilation technique (MAT) almost nullified control by SIT due to the mortality induced on sterile flies. The model suggested that the most rapid decrease in population size would be achieved by SIT plus protein baits. However, the model predicted both the SIT and protein baits when used alone would result in population reduction. The MAT can be used prior to SIT release to increase overflooding ratios.     

Effects of temperature and relative humidity on mating and survival of sterile Drosophila suzukii

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a widely distributed pest species of soft-skinned fruits. Recent studies suggest the use of sterile insect technique (SIT) as a control method for this species; however, many factors can impact effectiveness of a SIT programme, including the environmental conditions. Environmental condition is critical at the time of the release and in the days afterwards, since it may impact sterile insects’ survival and ability to mate. Thus, we verified the influence of temperature and relative humidity on mating and survival of fertile and sterile D. suzukii, when insects were food provided or deprived. Highest mating rates occurred when sterile or fertile flies provided with food were exposed to 25ºC or 81%–100% relative humidity, while temperatures of 10 and 35ºC and humidity below 60% impaired mating. Overall, mating rate among food-deprived flies was low in all temperatures and humidity levels tested, but fertile insects were more prone to mate when compared to sterile flies. Survival was negatively influenced by high temperatures, low relative humidity and food deprivation. The information present in this study is useful to be considered for release of sterile D. suzukii.     

Pre-release feeding on yeast hydrolysate enhances sexual competitiveness of sterile male Queensland fruit flies in field cages

Recent laboratory studies of mass‐reared flies in small cages have found that periods of just 24‐ or 48‐h access to yeast hydrolysate can substantially enhance mating performance of mass‐reared male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (‘Q‐flies’). Using field cage tests that provide a better approximation of nature, we here investigated whether access to yeast hydrolysate for 48 h after adult emergence improves the ability of male and female mass‐reared, sterile Q‐flies to compete sexually with wild‐type flies that had been provided continuous access to yeast hydrolysate. Mating probability of sterile males was significantly increased by 48‐h access to yeast hydrolysate; sterile males provided 48‐h access to yeast hydrolysate had mating probability similar to that of wild males provided continuous access to yeast hydrolysate, whereas sterile males deprived of access to yeast hydrolysate had much lower mating probability. Unlike males, access to yeast hydrolysate for 48 h did not increase mating probability of sterile female Q‐flies. We instead found that wild females provided continuous access to yeast hydrolysate had higher mating probability than sterile females that did or did not have 48‐h access to yeast hydrolysate. This result raises the possibility that a bisexual Q‐fly strain might operate essentially as a male‐only release when the flies are given access to yeast hydrolysate during a 48‐h pre‐release holding period. Sterile males given access to yeast hydrolysate for 48 h mated significantly earlier in the evening than wild males and, as in other recent studies, this tendency was associated with an increased tendency to mate on the trees rather than the cage walls. There was no evidence of sexual isolation in this study, as wild and sterile mass‐reared flies showed no evidence of preferential mating with their own kind. Further studies are now needed to assess the potential for pre‐release access to yeast hydrolysate to improve sexual performance and longevity of sterile, mass‐reared, Q‐flies in the field.     

Effect of irradiation on mating performance and mating ability in the West Indian sweetpotato weevil, Euscepes postfasciatus

The sterile insect technique (SIT) is widely used for suppressing or eradicating target pest insect populations. The effectiveness of SIT depends on the ability of released sterile males to mate with and inseminate wild females. Irradiation not only damages the reproductive cells but the somatic cells as well. The mating behavior of irradiated males may be altered over time due to the depressed metabolic activity brought about by sterilization. In this study, we evaluated the mating behavior (copulation behavior, mating performance, and ability of sperm transfer) of irradiated males in Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae) for 16 days after irradiation in the laboratory. The mating performance of males irradiated with a 150 Gy dose, as currently used in the SIT program in Okinawa prefecture for E. postfasciatus, decreased compared to that of control after day 7. As a result, we considered that irradiation had no major effect on male mating behavior for approximately 1 week after irradiation.     

An egg‐laying device to estimate the induction of sterility in Ceratitis capitata (Diptera: Tephritidae) sterile insect technique programmes

Area‐wide environmentally friendly pest control methods such as the sterile insect technique (SIT) are being developed and improved to contribute in managing agricultural, environmental and public health problems. A key aspect to evaluate performance of sterile males is to directly measure sterility induction in the field. Sterility induction has been estimated for tephritid fruit flies by recovering egg from host fruit in the field, the method is, however, impractical, and past efforts to develop artificial egg‐laying devices have not prospered. Here, we evaluated response of wild gravid Ceratitis capitata (Medfly) females to long‐distance fruit‐based chemical attractants, visual and tactile stimuli to develop an artificial egg‐laying device. The device combining the most attractive features was further tested under two deployment schemes. Finally, devices and deployment tactics were used to compare fertility levels between feral Medfly females under conventional management and under SIT. Agar spheres wrapped in plastic film, baited with pressed peach juice and visually enhanced with yellow discs received more egg than other combinations of attractive features. Such devices also received more eggs when deployed on fruitless trees and when placed on the orchard perimeter. The egg hatch in an orchard under conventional management was estimated at 86%, whilst egg hatch in an area under SIT was reduced to 31%. The egg‐laying devices are therefore useful to measure sterility induction and can be further improved by refining long‐distance attraction and deployment schemes.     

Precocious Mexican fruit fly methoprene‐fed males inhibit female receptivity and perform sexually as mature males

The sterile insect technique (SIT) has been used successfully for the control of fruit flies. The efficiency of this technique can be significantly reduced when sterile released insects are exposed to adverse conditions and predators, as a great number of sterile insects die before reaching sexual maturity and thus fail to mate with wild females. Treatments with juvenile hormone (JH) analogues such as methoprene (M) significantly reduce the time to reach sexual maturity by sterile Anastrepha ludens (Loew) (Diptera: Tephritidae) males. In this study, we compared the sexual performance of non‐treated sexually mature males with young males that had been sexually accelerated with M. Furthermore, we compared the ability of M‐fed males in inhibiting female remating compared with sexually mature males. Results showed that at 5 days M‐fed males had lower mating success than mature males; however, 6‐day‐old (0.1%) M‐fed males had the same amount of matings as mature 13‐day‐old males. Young 5‐ to 10‐day‐old M‐fed males also had similar number of matings as mature non‐treated 12‐ to 17‐day‐old males. There were no differences in copula duration between treatments. Moreover, there were no differences between the fertility, fecundity or refractory period of females mated with either young male fed M or normal sexually mature males. These results indicated that young males that were sexually accelerated with M have the same sexual performance as non‐treated sexually mature males. Implications of using M as a pre‐release treatment for A. ludens controlled through SIT are discussed.     

Laboratory adaptation reduces female mating resistance in the sweet potato weevil

Selection for genetic adaptation might occur whenever an animal colony is maintained in the laboratory. The laboratory adaptation of behavior such as foraging, dispersal ability, and mating competitiveness often causes difficulties in the maintenance of biological control agents and other beneficial organisms used in procedures such as the sterile insect technique (SIT). Sweet potato weevil, Cylas formicarius (Summers) (Coleoptera: Brentidae), is an important pest in sub‐tropical and tropical regions. An eradication program targeting C. formicarius using SIT was initiated in Japan with weevils being mass‐reared for 95 generations to obtain sufficient sterile males. The mass‐reared strain of C. formicarius exhibits weaker female resistance to male mating attempts compared with the wild strain. This could affect the success of SIT programs because mating persistence of mass‐reared males might be expected to decrease in response to weak female resistance. We show that high success of sperm transfer to mass‐reared females was due to weak female resistance to male mating attempts. However, the mating behavior of mass‐reared males did not change. In C. formicarius, the trait of male persistence to mate was not correlated with the female resistance traits. Our results suggest that mass‐rearing conditions do not have negative effects on the mating ability of the sterile males of this species, and thus that the current mass‐rearing procedures are suitable for production of sterile males for the weevil eradication program.     

Improving male mating competitiveness and survival in the field for medfly,Ceratitis capitata (Diptera: Tephritidae) SIT programs

The success of the sterile insect technique (SIT) depends critically upon mating between released sterilized males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts – mating enhancement and survival improvement. In the former, two methods have been investigated – selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control flies. Regarding mating selection, standard laboratory-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, laboratory-reared males were exposed to ginger root oil for several hours 1 day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, irradiation reduced this increase to ca. 2.5-fold. Exposing the selected, hybrid strain raised the fitness of the lab males to ca. 9-fold that of wild males. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. 2-fold better than laboratory control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.     

Sex ratio and the role of mild relative humidity in mating behaviour of red date palm weevil Rhynchophorus ferrugineus Oliv. (Coleoptera: Curculionidae) gamma‐irradiated adults

The influence of gamma radiation on the mating behaviour of the red date palm weevil (RDPW), Rhynchophorus ferrugineus (Olivier), and the efficacy of sterile insect technique (SIT) under different levels of relative humidity (RH) were studied. No adverse effects of gamma radiation were observed on the mating behaviour parameters of the RDPW, such as mate recognition time, mating duration, mating frequency within a 30‐min period and duration between consecutive matings. However, the weevils were sexually stimulated during aggregation. RH significantly affected egg laying as well as egg hatching. Significantly lower egg laying and hatching were recorded at 25% RH than at higher humidity levels, suggesting that low humidity conditions are better for successful SIT manipulations in the field. Lifespan of irradiated RDPW males was significantly shorter than that of un‐irradiated controls, irrespective of RH level.     

Optimizing methyl‐eugenol aromatherapy to maximize posttreatment effects to enhance mating competitiveness of male Bactrocera carambolae (Diptera: Tephritidae)

Methyl‐eugenol (ME) (1,2‐dimethoxy‐4‐(2‐propenyl)benzene), a natural phytochemical, did enhance male Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae) mating competitiveness 3 d after ingestion. Enhanced male mating competitiveness can significantly increase the effectiveness of the sterile insect technique (SIT). ME application to mass reared sterile flies by feeding is infeasible. ME application by aromatherapy however, would be a very practical way of ME application in fly emergence and release facilities. This approach was shown to enhance mating competitiveness of B. carambolae 3 d posttreatment (DPT). Despite this added benefit, every additional day of delaying release will reduce sterile fly quality and will add cost to SIT application. The present study was planned to assess the effects of ME‐aromatherapy on male B. carambolae mating competitiveness 1DPT and 2DPT. ME aromatherapy 1DPT or 2DPT did enhance mating competitiveness of B. carambolae males whereas ME feeding 1DPT and 2DPT did not. Male mating competitiveness was enhanced by the ME aromatherapy irrespective if they received 1DPT, 2DPT or 3DPT. ME aromatherapy, being a viable approach for its application, did enhance mating competitiveness of male B. carambolae 1 d posttreatment as ME feeding did 3 d after ingestion.