Overflooding Ratios Research Articles

Releasing incompatible males drives strong suppression across populations of wild and Wolbachia-carrying Aedes aegypti in Australia

Releasing sterile or incompatible male insects is a proven method of population management in agricultural systems with the potential to revolutionize mosquito control. Through a collaborative venture with the "Debug" Verily Life Sciences team, we assessed the incompatible insect technique (IIT) with the mosquito vector Aedes aegypti in northern Australia in a replicated treatment control field trial. Backcrossing a US strain of Ae. aegypti carrying Wolbachia wAlbB from Aedes albopictus with a local strain, we generated a wAlbB2-F4 strain incompatible with both the wild-type (no Wolbachia) and wMel-Wolbachia Ae. aegypti now extant in North Queensland. The wAlbB2-F4 strain was manually mass reared with males separated from females using Verily sex-sorting technologies to obtain no detectable female contamination in the field. With community consent, we delivered a total of three million IIT males into three isolated landscapes of over 200 houses each, releasing ∼50 males per house three times a week over 20 wk. Detecting initial overflooding ratios of between 5:1 and 10:1, strong population declines well beyond 80% were detected across all treatment landscapes when compared to controls. Monitoring through the following season to observe the ongoing effect saw one treatment landscape devoid of adult Ae. aegypti early in the season. A second landscape showed reduced adults, and the third recovered fully. These encouraging results in suppressing both wild-type and wMel-Ae. aegypti confirms the utility of bidirectional incompatibility in the field setting, show the IIT to be robust, and indicate that the removal of this arbovirus vector from human-occupied landscapes may be achievable.

Development of Sterile Insect Technique for Control of the European Grapevine Moth, Lobesia botrana, in Urban Areas of Chile.

The European grapevine moth, a Palearctic pest, was first detected in the Americas in 2008. Its establishment in Chile presented production and export issues for grapes and other fruits, and a national control campaign was launched. Urban areas next to agricultural production areas were recognized as a challenge for effective control. In 2015, a SIT laboratory was established in Arica, Chile to evaluate its potential for urban control. Progress included the development and evaluation of artificial diets, a mass-rearing of 75,000 moths/week, confirmation of 150 Gy as an operational dose for inherited sterility, and releases of sterile moths in a 25 ha urban area next to fruit production areas. Season-long releases demonstrated that high overflooding ratios were achieved early in the season but decreased with a large increase in the wild moth population. Sterile moth quality was consistently high, and moths were observed living in the field up to 10 days and dispersing up to 800 m. Recommendations for further development of the SIT include conducting cage and field studies to evaluate overflooding ratios and mating competitiveness, measuring of infestation densities in release and no-release areas, and conducting trials to evaluate combining SIT with compatible integrated pest management (IPM) tactics such as fruit stripping and use of mating disruption.

Management and eradication options for Queensland fruit fly

AbstractSeveral 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.

Inherited Sterility inTuta absoluta(Lepidoptera: Gelechiidae): Pest Population Suppression and Potential for Combined Use with a Generalist Predator

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most devastating pests of tomato. We studied whether partially sterile T. absoluta males and fully sterile females were capable of suppressing wild populations of this moth in semi-controlled conditions. After irradiating T. absoluta pupae with 200 Gy, emerged males and females were released at 10:1 (treated:untreated) and 15:1 over-flooding ratios inside field cages containing tomato plants. The number of eggs and larvae produced was recorded once per wk during 3 mo. An over-flooding ratio of 10:1 caused a decline in larvae production compared with the untreated control cages, but these differences were not statistically significant. Using an over-flooding ratio of 15:1, the moth population in the cages with irradiated insects decreased significantly compared with those in the untreated control cages. In addition, the possibility of combining inherited sterility and a natural enemy as a strategy to manage this pest was investigated. We studied in no choice and choice tests the predation behavior of females of the egg predator Tupiocoris cucurbitaceus (Hemiptera: Miridae) on eggs derived from the following parental T. absoluta crosses: FU × MU (control), FU × MI and FI × MU (where U = untreated, I = irradiated). In the no choice test, females of the T. cucurbitaceus readily consumed T. absoluta eggs regardless of their origin. In the choice test, T. cucurbitaceus females consumed similar numbers of eggs of untreated parents and eggs oviposited from crosses in which the male had been irradiated. However, the mirid females preyed on significantly more eggs—roughly 20% more—from irradiated females than on eggs from untreated females. We conclude that it is possible to achieve a certain level of suppression of a T. absoluta wild population through the release of irradiated insects, and that it is technically feasible to combine the use of the predator T. cucurbitaceus with inherited sterility to control this moth pest. ResumenTuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) es una de las plagas mas devastadoras de los cultivos de tomate. Se estudio si machos parcialmente esteriles y hembras totalmente esteriles de T. absoluta son capaces de suprimir poblaciones salvajes de esta polilla en condiciones semicontroladas. Despues de la irradiacion de pupas de T. absoluta a 200 Gy, machos y hembras emergidos fueron liberados con una relacion de 10:1 (tratados:no tratados) en el interior de jaulas que contenian plantas de tomate. El numero de huevos y larvas producido fue registrado una vez a la semana durante tres meses. El experimento se repitio con una relacion de 15:1. El uso de una relacion de 10:1 causo una disminucion de la poblacion de larvas en comparacion con las jaulas control, pero estas diferencias no fueron estadisticamente significativas. Cuando la relacion fue 15:1, la poblacion de la polilla en las jaulas con los insectos irradiados disminuyo significativamente en comparacion con las jaulas control. Ademas, se analizo la posible compatibilidad de la esterilidad heredada y el control biologico como estrategia para el control de esta plaga. Se estudio en pruebas sin eleccion y con eleccion si los huevos provenientes de los siguientes cruzamientos parentales de T. absoluta: HU × MU (control), HU × MI y HI × MU (donde U = no irradiado, I = irradiado) son igualmente aceptados para el consumo por hembras de Tupiocoris cucurbitaceus (Hemiptera: Miridae). En la prueba sin eleccion, las hembras de T. cucurbitaceus consumieron un elevado numero de huevos de T. absoluta, independientemente de su origen. En la prueba de eleccion, las hembras de T. cucurbitaceus consumieron tanto huevos provenientes de parentales no tratados como huevos de parentales con el macho irradiado. Sin embargo, las hembras del mirido predaron significativamente mas huevos de hembras irradiadas que huevos de hembras no tratadas. Se concluyo que es posible alcanzar un cierto nivel de supresion de una poblacion salvaje de T. absoluta mediante la liberacion de insectos irradiados y que es factible combinar el uso del predador T. cucurbitaceus con IS para controlar esta polilla plaga. View this article in BioOne

Sterile Insect Releases for Control ofThaumatotibia leucotreta(Lepidoptera: Tortricidae): An Assessment on Semi-Commercial Scale

False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is indigenous to sub-Saharan Africa. It infests a large number of wild plants and can be a pest of commercial concern in cultivated fruit and nuts. A limited number of insecticides, as well as biological control and mating disruption can be applied as control measures in citrus, but they often do not reduce pre- and post-harvest crop loss adequately. The potential of the sterile insect technique (SIT) for the control of T. leucotreta was investigated between 2002 and 2006 in Citrusdal, Western Cape Province, South Africa, and entailed studies on radiation biology and F1 sterility, compatibility with the egg parasitoid Trichogrammatoidea Nagaraja (Hymenoptera: Trichogrammatidae), and field cage experiments to determine sterile:fertile moth overflooding ratios. Promising results justified a pilot experiment conducted on semi-commercial scale in citrus orchards in Citrusdal during 2005–06. One thousand mixed sex moths were tre...

Sterile Insect Technique and Control of Tephritid Fruit Flies: Do Species With Complex Courtship Require Higher Overflooding Ratios?

The sterile insect technique (SIT) is widely used to suppress or eradicate tephritid fruit fly pests that threaten agricultural crops. The SIT entails the production, sterilization, and release of large numbers of the target pest species, with the goal of achieving sterile male by wild female matings, which result in infertile eggs and the subsequent reduction of the wild pest population. The success of this control strategy depends, to a large extent, on the ability of released, sterile males to compete successfully against wild males to achieve copulations with wild females. Lance and McInnis (2005) proposed that species with greater male involvement in courtship and mating are less amenable to the SIT than species with simple courtship, because strong artificial selection characteristic of mass-rearing environments is more likely to generate greater behavioral modification to complex than simple courtship and thus to result in increased rejection by wild females. Consistent with Lance and McInnis (2005), the mating competitiveness of mass-reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), a species with complex male courtship, is substantially lower than that of mass-reared males of the melon fly, Bactrocera cucurbitae (Coquillett), or the oriental fruit fly, Bactrocera dorsalis (Hendel), two species with very simple male courtship. In light of this difference in mating ability, we tested the prediction that higher overflooding ratios (sterile:wild males; OFR) would be required to control populations of C . capitata than of the Bactrocera spp. Levels of induced egg sterility achieved under different OFRs were compared to the “net sterility target,” computed as the proportional decrease in a species’ intrinsic birth rate (realized via SIT) required to balance the intrinsic rate of death and found to be ∼80% for the three species considered. Although the data are scant, they generally support the prediction. For B . cucurbitae , OFRs 300:1. Likewise, relative to populations in control (untreated) sites, populations in release areas were reduced >99% at OFRs of 50:1–100:1 for B . cucurbitae in Japan compared to reductions for C . capitata of 50–93% at OFRs between 700:1–3,160:1 in Nicaragua and about 80% for OFRs between 100:1–400:1 in Hawaii. The implications of these findings for fruit fly SIT are discussed.

Yeast hydrolysate supplementation increases field abundance and persistence of sexually mature sterile Queensland fruit fly,Bactrocera tryoni(Froggatt)

The sterile insect technique (SIT) is a non-chemical approach used to control major pests from several insect families, including Tephritidae, and entails the mass-release of sterile insects that reduce fertility of wild populations. For SIT to succeed, released sterile males must mature and compete with wild males to mate with wild females. To reach sexual maturity, the Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), must obtain adequate nutrition after adult emergence; however, in current SIT programs sterile B. tryoni receive a pre-release diet that lacks key nutrients required to sustain sexual development. The chief objective of this study was to determine whether pre-release yeast hydrolysate (YH) supplements affect the persistence and abundance of sexually mature sterile male B. tryoni under field conditions. Experiments were run in outdoor cages under conditions of low and high environmental stress that differed markedly in temperature and humidity, and in the field. Under low environmental stress conditions, survival of sterile B. tryoni was monitored in cages under three diet treatments: (i) sugar only, (ii) sugar plus YH or (iii) sugar plus YH for 48h and sugar only thereafter. Under high environmental stress conditions survival of sterile B. tryoni was monitored in cages under four diet treatments: (i) white sugar only, (ii) brown sugar only, (iii) white sugar plus YH and (iv) brown sugar plus YH. In a replicated field study, we released colour-marked sterile B. tryoni from two diet regimes, YH-supplemented or YH-deprived, and monitored abundance of sexually mature males. In the low-stress cage study, there was no effect of diet, although overall females lived longer than males. In the high stress cage study, mortality was lower for YH-fed flies than YH-deprived flies and females lived longer than males. In the field, YH supplementation resulted in higher abundance of sexually mature sterile males, with 1.2 YH-fed flies trapped for every YH-deprived fly trapped. Under field conditions, YH supplementation can increase over-flooding ratios and hence may improve the effectiveness of SIT programmes.

Attractiveness and competitiveness of irradiated light brown apple moths

AbstractThe sterile insect technique (SIT) potentially provides a socially acceptable approach for insect eradication of new pest incursions. The light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), was discovered in Berkeley (CA, USA) in 2006, leading to an incursion response that included this technology. In this study, we assessed factors affecting mating success from a bisex release of irradiated moths: effects of radiation dose on male multiple mating, male flight competition, female sex pheromone titre and attractiveness of irradiated females to males, and identification of successful mating in vineyards of either irradiated or wild males (identified by isotope analysis of spermatophores from sentinel females). There was a significant negative relationship between male radiation dose and mating frequency. In head‐to‐head flights of irradiated males against non‐irradiated males to a pheromone lure in a wind tunnel, irradiated males reached the lure first only 31% of the time. With increasing radiation dose, the production of the major sex pheromone component in females, (E)‐11‐tetradecenyl acetate, dropped, from 0.7 ± 0.1 ng per female in non‐irradiated females to 0.2 ± 0.07 ng per female when irradiated at 300 Gy. Male catch was reduced to 11% of control females in traps containing females irradiated at 300 Gy. Isotope analysis of spermatophores found in the bursa copulatrix of females indicated that mating success of irradiated males inside the live (entry‐only) traps containing virgin females was lower (13.1 ± 3.3%) than suggested by male catch (21.2 ± 3.8%) in pheromone traps, the current standard for assessing field competitiveness. Impacts of irradiation on male and female moth fitness should be taken into account to improve estimates of irradiated to wild male E. postvittana overflooding ratios needed for population suppression.

Comparative Fitness of Irradiated Light Brown Apple Moths (Lepidoptera: Tortricidae) in a Wind Tunnel, Hedgerow, and Vineyard

Light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), is the target of the sterile insect technique, but reduced moth fitness from irradiation lowers the effective overflooding ratio of sterile to wild moths. New measures of insect quality are being sought to improve field performance of irradiated insects, thus improving the cost effectiveness of this technique. Male pupae were irradiated at intervals between 0 and 300 Gy, and adult flight success was assessed in a wind tunnel equipped with flight track recording software. A dose response was evident with reduced successful search behaviors at higher irradiation doses. Irradiation at 250 Gy reduced arrival success to 49% of untreated controls, during 2-min assays. Mark-release-recapture of males irradiated at 250 Gy indicated reduced male moth recapture in hedgerows (75% of control values of 7.22% +/- 1.20 [SEM] males recaptured) and in vineyards (78% of control values 10.5% +/- 1.66% [SEM] recaptured). Males dispersed similar distances in both habitats, and overflooding ratios dropped off rapidly from the release point in both landscapes. Transects of traps with central releases proved to be an efficient method for measuring the quality of released males. Relative field performance of moths was greater than suggested by wind tunnel performance, which could be due to time differences between the two assays, two-minute wind tunnel tests compared with days in the field treatments. Release strategies involving ground releases should consider the effect of limited postrelease dispersal. Aerial release could solve this problem and warrants investigation.

Exposure of sterile Mediterranean fruit fly (Diptera: Tephritidae) males to ginger root oil reduces female remating

AbstractFemales of Ceratitis capitata are facultative polyandrous, with remating more common in laboratory strains rather than wild ones. In the application of the Sterile Insect Technique (SIT) against this pest, large overflooding ratios of sterile : wild males can increase the remating frequency. Females that mate for the first time with a sterile male tend to remate more frequently. The exposure of sterile males to ginger root oil (GRO) is used in C. capitata SIT programmes to increase the sterile male mating success. Exposing males to an ‘aromatherapy’ with GRO may also increase the remating frequency among wild females. The frequency of wild females remating, number of matings per female, the refractory period between the first and second mating, and the duration of the first and second matings of wild females were determined under laboratory conditions for three mating scenarios that included wild males only or wild males competing with sterile males (either GRO‐treated or non‐treated). Wild females first mated with sterile males exposed to GRO had their remating rate over the following 6 days and the mean number of matings per female reduced in comparison to those first mated with non‐exposed sterile males, from 62.5% to 32.2% and from 3.1 to 1.6 respectively. The remating parameters of females mated with sterile GRO‐exposed males resembled those of females mated with wild males.

A dynamic population model for tsetse (Diptera: Glossinidae) area‐wide integrated pest management

AbstractA spatial model of tsetse (Glossina palpalis ssp. and G. pallidipes) life cycle was created in FORTRAN, and four control measures [aerial spraying of non‐residual insecticides, traps and targets, insecticide‐treated livestock (ITL) and the sterile insect technique] were programmed into the model to assess how much of each of various combinations of these control tactics would be necessary to eradicate the population. The model included density‐independent and ‐dependent mortality rates, temperature‐dependent mortality, an age‐dependent mortality, two mechanisms of dispersal and a component of aggregation. Sensitivity analyses assessed the importance of various life history features and indicated that female fertility and factors affecting survivorship had the greatest impact on the equilibrium of the female population. The female equilibrium was likewise reduced when dispersal and aggregation were acting together. Sensitivity analyses showed that basic female survivorship, age‐dependent and temperature‐dependent survivorship of adults, teneral‐specific survivorship, daily female fertility, and mean temperature had the greatest effect on the four applied control measures. Time to eradication was reduced by initial knockdown of the population and due to the synergism of certain combinations of methods [e.g., traps‐targets and sterile insect technique (SIT); ITL and SIT]. Competitive ability of the sterile males was an important parameter when sterile to wild male overflooding ratios were small. An aggregated wild population reduced the efficiency of the SIT, but increased it with increased dispersal. The model can be used interactively to facilitate decision making during the planning and implementation of operational area‐wide integrated pest management programs against tsetse.

Cytological Attributes of Sperm Bundles Unique to F1Progeny of Irradiated Male Lepidoptera: Relevance to Sterile Insect Technique Programs

ABSTRACT The unique genetic phenomena responsible for inherited F1 sterility in Lepidoptera and some other arthropods provide advantages for the use of inherited sterility in a sterile insect technique (SIT) program. Lepidopteran females generally can be completely sterilized at a dose of radiation that only partially sterilizes males of the same species. When these partially sterile males mate with fertile females, many of the radiation-induced deleterious effects are inherited by the F1 generation. At the appropriate dose of radiation, egg hatch of females mated with irradiated males is reduced and the resulting (F1) offspring are both highly sterile and predominantly male. Lower doses of radiation used to induce F1 sterility increase the quality and competitiveness of the released insects. However, during a SIT program it is possible that traps used to monitor wild moth populations and over-flooding ratios (marked released males vs unmarked wild males) may capture unmarked F1 sterile males that cannot ...

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.

Is lack of mating competitiveness in spring linked to mating asynchrony between wild and mass‐reared codling moths from an operational sterile insect programme?

AbstractMating competitiveness and pheromone trap catches of mass‐reared, male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), from the Osoyoos, British Columbia, Canada, mass‐rearing facility operated by the Okanagan‐Kootenay Sterile Insect Release Board, were compared to wild males using mark–release–recapture field experiments in spring, summer, and autumn at Summerland, British Columbia. In spring, significantly more wild diapause males mated with tethered, wild females than did non‐irradiated (0 Gy) or irradiated (100 or 250 Gy) non‐diapause, mass‐reared males. A lower dose of radiation did not improve mating competitiveness, nor catches of mass‐reared males released in spring. Median mating time for wild males was approximately 45 min earlier than mass‐reared males with most wild males (70.5%) mating before sunset and mass‐reared males mating at or shortly after sunset in spring. Superior mating competitiveness of wild males in spring was mirrored by greater recapture rates in pheromone‐baited traps. In summer, mating competitiveness of mass‐reared moths improved relative to wild males and there was a significant inverse relationship between radiation dose (0, 100, and 250 Gy) and competitiveness of mass‐reared males. In autumn, untreated, wild males were significantly more responsive to pheromone traps than non‐diapausing mass‐reared males receiving 250 Gy of radiation. Mass‐reared males, subjected to diapause‐inducing conditions as larvae and emerged from diapause before this irradiation treatment, were recaptured significantly more often than similarly irradiated, non‐diapause, mass‐reared males, but not more than untreated, diapause wild males. We hypothesize that differences between wild and mass‐reared males in daily timing or speed of responses to natural or synthetic pheromone sources under montane weather patterns typical of spring in British Columbia may partially explain poor activity of sterile males, and low sterile : wild overflooding ratios during spring when measured using pheromone traps by the sterile insect release programme in British Columbia.

The sterile insect technique and the Mediterranean fruit fly: assessing the utility of aromatherapy in large field enclosures

AbstractThe sterile insect technique (SIT) is widely used in integrated programs against tephritid fruit flies, 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 male mating competitiveness. One potential solution involves the prerelease exposure of males to particular 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. To evaluate more rigorously the effectiveness of GRO exposure, we here describe two projects that compared levels of egg sterility or pupal yield, respectively, following the release of wild flies and either GRO‐exposed (treated) sterile males or GRO‐deprived (control) sterile males in large field enclosures. In both projects, sterile males from a genetic sexing strain were exposed as adults to GRO for 24 h while held in large storage boxes. In Hawaii, we dissected eggs from fruits to determine the percentage of egg hatch at four overflooding ratios, ranging from 5 : 1 to 60 : 1 (sterile : wild males), and found that, at all four ratios, the proportion of unhatched (sterile) eggs was significantly greater in enclosures containing GRO‐exposed males than control males. In Guatemala, we allowed larvae to develop in fruits and counted the number of pupae produced. At the only overflooding ratio tested (25 : 1), pupal yield was approximately 25% lower for enclosures containing GRO‐exposed males than control males, although this difference was not statistically significant. An explanation for the differing outcomes is proposed, and the implications of these findings for the SIT are discussed.

Potential for Reducing Overflooding Ratios of Sterile Mediterranean Fruit Flies (Diptera: Tephritidae) with the Use of Ginger Root Oil

Abstract The mating behavior of sterile, laboratory-reared, male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), was evaluated in field-cage mating competition tests with wild flies after exposing the laboratory males to ginger root oil extract. Without exposure to ginger root oil, sterile males obtained 12.6%, 69.0%, and 72.8% of the total matings with wild females when present in 1:1, 5:1, and 10:1 ratios of sterile males to wild males, respectively. Sterile males, exposed to ginger root oil for 3 h, 1 d before mating trials, in a 1:1 ratio with wild males, achieved 62.3% of the matings with wild females. These data suggest that exposure to ginger oil can elevate sterile male mating competitiveness to a similar degree as elevated ratios of sterile to wild males. Incorporating the use of ginger root oil extract into sterile release programs may thus increase the effectiveness of the sterile insect technique, and/or allow a reduction in the number of sterile flies that are released.

A PERSONAL ACCOUNT OF DEVELOPING THE STERILE INSECT TECHNIQUE TO ERADICATE THE SCREWWORM FROM CURACAO, FLORIDA AND THE SOUTHEASTERN UNITED STATES

The history is recounted of developing the sterile insect technique to eradicate the screwworm, Cochliomyia hominivorax (Coquerel), from the Caribbean island of Curacao, Florida and the southeastern U.S. Observations of screwworm biology and challenges faced in conducting these eradication projects are described by the author who worked on all aspects of the research and field operations. Eradication was first demonstrated on Curacao, essentially a 170 mi2 outdoor laboratory. The population dynamics of the wild screwworm was determined and overflooding ratios and dispersal patterns essential for population suppression were defined. Eradication was achieved with minimal resources by attacking the pest during the time of year when it is least abundant. In Florida, eradication was greatly facilitated by an unusually cold winter that reduce the range and density of the target population. Eradication could not be attained easily by only suppressing the reproduction of adult screwworms. The larval population also had to be reduced to increase the ratio of sterile to wild males. It was essential to control the immature stages by diligent inspection and treatment of animal wounds. Leadership of the cattle producers was critical not only for securing program resources from the clientele, state legislatures and U.S. Congress, but also for gaining the cooperation of virtually all livestock owners. Additionally, leadership was required to acquire adequate research, extension and public information resources. Lessons learned from this work were corroborated repeatedly as the screwworm eradication program moved into the Southwest, Mexico and the Central America.

A Rapid Method for Identifying Dye-Marked Fruit Flies2

During large-scale evaluations of the sterile insect release method for eradicating fruit flies in the Mariana Islands and Hawaii in 1962–63, (Steiner et al. in press) a rapid method was needed for separating sterile flies from those that had emerged and dispersed naturally. The 5 to 10 million flies that were released weekly required periodic identification of marked individuals in 1800 trap collections to show overflooding ratios attained, dispersal, and longevity. Existing methods did not permit adequate sampling of the fly populations.