Development of Aerial Releases of Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae), a Parasitoid that Attacks the Mediterranean Fruit Fly, Ceratitis capitata (Weidemann) (Diptera: Tephritidae), in the Guatemalan Highlands

A braconid parasitoid, Diachasmimorpha tryoni (Cameron), was released from the air into Guatemalan coffee plantations that contained Mediterranean fruit flies, Ceratitis capitata (Weidemann). Parasitoid adults were chilled, placed in paper bags, and dropped from an altitude of 100 m and at an airspeed of ~ 130 km/h. Releases were made at four different densities over a period of two years. At the higher release rates parasitism levels reached as high as 84%. The feasibility of using a more technically sophisticated aerial release technique, the auger sterile-insect release machine utilized in C. capitata sterile-fly aerial eradication projects in California and Florida, was also examined. Chilled D. tryoni either alone or in combination with chilled, sterile C. capitata , were dropped over target areas and the released parasitoids examined for mortality and damage. Samples of released parasitoids were taken and tested for 'flight ability'; i.e. flight response after an opportunity to recover from chilling. There was no evidence of significant mortality due to aerial release, and the flight-ability of insects released at various rates and altitudes did not significantly differ from chilled controls that were not released from an airplane.     

Rearing of the fruit fly parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) on X-ray irradiated larvae of Ceratitis capitata (Diptera: Tephritidae)

We evaluated the effects of X-ray irradiation on larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), with the aim of finding a treatment that prevented adult fly emergence, yet did not adversely affect larval quality as rearing hosts for the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Ichneumonidae). Two experiments were carried out. In the first experiment, small numbers of larvae were held in Petri dishes with and without small amounts of rearing media and then irradiated with doses of X-rays ranging from 0 to 8333.6 R (equivalent to 80 Gy). In the second experiment, higher numbers of larvae were held in a manner resembling mass-rearing conditions, and were then irradiated with X-rays ranging from 0 to 10,417 R (equivalent to 100 Gy). In both experiments, the only factor that significantly affected fly emergence was irradiation of larvae. Fly emergence decreased markedly as the irradiation dose increased, and complete suppression of fly emergence was achieved at 6250.2 R (equivalent to 60 Gy) when larvae were irradiated in small batches with or without rearing media. Irradiation also affected the fertility of those flies that did emerge following treatment. In the second experiment, we found the parasitoids reared from irradiated larvae produced a higher parasitism rate and a higher number of female offspring than did parasitoids reared from control (non-irradiated) larvae. Mean fecundity of F1 parasitoids reared from irradiated larvae were affected positively by irradiation only at the 8333.6 R (80 Gy) dose. Our results show that X-ray irradiation can be used to inhibit fruit fly adult emergence and that irradiated larvae are at least as good a rearing substrate as non-irradiated larvae. Future studies should focus on the adjustment of our findings to a mass-rearing scale.     

Scent Marking by Males of the Mediterranean Fruit Fly, Ceratitis capitata (Diptera: Tephritidae)

Males of the Mediterranean fruit fly, Ceratitis capitata (medfly), defend individual leaves as mating territories. While perching, males release an air-borne pheromone (known to attract females) from everted rectal epithelium at the tip of the abdomen. Males also occasionally touch the substrate with the tip of their abdomen. The main objective of the present study was to determine whether such abdomen dipping was a form of intersexual signaling, i.e., whether this action resulted in increased female visitation to the territory. Following observations on the frequency of pheromone calling and abdomen dipping of individually marked males, I ran a standard set of experiments using leaves from four different plant species. Leaves were exposed to varying numbers of (mature) males and females, respectively, for varying durations, and female settlement was compared on exposed versus nonexposed leaves in laboratory cages. Exposing leaves to females had no, or little, influence on female distribution for any of the four plant species. Exposing leaves to males had little influence on subsequent female settlement for orange, coffee, or macadamia trees. However, leaves of the fig tree Ficus bejamina that were exposed to males were much more attractive to females than nonexposed leaves. I then conducted a series of additional tests using fig leaves and found that i) leaf exposure to immature males had no effect on female distribution, ii) leaf exposure to mature males for as little as 90 min increased leaf attractiveness to females, iii) prohibiting males direct contact with the leaf during exposure eliminated any effect on female settlement, and iv) females discriminated between exposed and nonexposed leaves even in physically complex environments (i.e., potted plants). The possible role of abdomen dipping in sexual advertisement of male medflies is discussed.     

Release of Sterile Mediterranean Fruit Flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), Using an Automated Ground Release Vehicle

A trial was conducted in Tampa, Florida to test an automated ground release machine as an alternative to aerial methods for release of sterile Mediterranean fruit flies, Ceratitis capitata (Wiedemann). Twenty-four Jackson traps baited with trimedlure at three release sites yielded lower than expected numbers of ground released Medflies. Recaptures per trap ranged from 2.8 (±0.7 S.E.) to 6.8 (±1.7 S.E.). Average recovery of sterile flies at each site for all releases combined (144 observations) was similar, 3.4 (±0.5 S.E.), 4.4 (±0.5 S.E.), 4.5 (±0.5 S.E.) for sites 1, 2 and 3 respectively. There was a significant reduction in flight ability from 67.5 (±2.1 S.E.) to 53.6 (±2.9 S.E.)%, from the time of pre-chilling to when immobilized flies were released after 2.5 h in the release container. Further tests are needed to determine what mortality factors may influence recovery and how the automated ground release machine compares to the aerial release method.     

Evaluation of Entomopathogenic Nematodes for the Control of Mediterranean Fruit Fly (Diptera: Tephritidae)

The virulence of various entomopathogenic nematode (EPN) strains was evaluated against the Mediterranean fruit fly, C. capitata . The selected nematodes were assessed for their infectivity for the final larval stage of the insect host and under varying environmental conditions. Among 12 EPN strains tested, Steinernema riobrave Texas ( Sr TX) and Heterorhabditis sp. IS-5 (H IS-5), showed high activity and induced >80% mortality. Six EPN strains showed limited activity (>30% mortality), and four strains had no effect (<20% mortality). Sr TX was more effective than H IS-5. Mature C. capitata larvae were most susceptible to nematode infection during the first 4h after they began to emerge from their diet to pupate. Activity of the two nematode strains at a constant inoculation rate was dependent on insect larval density. The highest activity was recorded at 1.88 larvae cm -2 and decreased at higher larval densities. EPN activity was also directly related to nematode density. Maximal activity was shown at a density of 150 infective juveniles cm -2 . A similar activity pattern was also recorded with Sr TX in four different soil types. The persistence of this EPN in the soil extended over 5 days but there was no activity after 14 days. Except for a lower activity under cool conditions (17°C), temperatures ranging between 22 and 41°C, or moisture levels in the treated soil ranging between 3 and 20%, had no significant effect on nematode activity. Our results suggest that application of Sr TX against C. capitata may have potential for controlling C. capitata .     

The isolation of microsatellite loci in the Mediterranean fruitfly Ceratitis capitata (Diptera: Tephritidae) using a biotin/streptavidin enrichment technique

The Medfly (Ceratitis capitata) is a polyphagous dipteran pest which has spread from North Africa to the countries of the Mediterranean Basin and has also invaded tropical and subtropical regions throughout the world. Colonizing populations typically possess low levels of genetic variability. Microsatellites provide an effective means of investigating the population structure of such genetically depauperate populations, however, microsatellite markers traditionally require a long phase of development in new taxa. We used a biotin/streptavidin capture technique to isolate microsatellites directly from C. capitata genomic DNA and we describe here the identification of seven polymorphic microsatellite markers in C. capitata.     

Effect of Two Opiine Parasitoids (Hymenoptera: Braconidae) Introduced for Fruit Fly Control on a Native Hawaiian Tephritid,Trupanea dubautiae(Diptera: Tephritidae)

Diachasmimorpha longicaudata(Ashmead) andPsyttalia fletcheri(Silvestri) are opiine parasitoids introduced into Hawaii for control of the Oriental fruit fly,Bactrocera dorsalis(Hendel) and the melon fly,Bactrocera cucurbitae(Coquillett), respectively. Both species have recently been mass-reared and released for research in augmentative biocontrol programs. Laboratory and field sleeve cage experiments were conducted to investigate the potential impact of mass-producedD. longicaudataandP. fletcherion a native Hawaiian tephritid,Trupanea dubautiae(Bryan), infesting the flowerheads of the native composite shrubDubautia raillardioidesHillebrand. Gravid females ofD. longicaudataandP. fletcheriwere confined with bloomingD. raillardioidesflowerheads infested with late instarT. dubautiae.BothD. longicaudataandP. fletcherilacked positive oviposition responses toT. dubautiaelarvae in infested flowerheads and caused neither parasitism nor mortality to the flies. However, when larvae were removed from the flowerheads and presented in screened dishes containing artificial diet of the parasitoids' normal rearing hosts (B. dorsalisandB. cucurbitae), bothD. longicaudataandP. fletcherireadily oviposited in the test larvae. Oviposition byD. longicaudatadid not significantly affect the percentage pupation ofT. dubautiae,but did reduce the emergence of adult flies. Oviposition byP. fletcherisignificantly reduced both pupation and adult fly emergence. All progeny of both parasitoid species died as eggs or first-instar larvae. Results from our experiments demonstrate that biological control programs targeted against frugivorous tephritid pests byD. longicaudataandP. fletcherihave no harmful impact on flowerhead-infestingT. dubautiae.     

Evaluation of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) as a mortality factor of Ceratitis capitata (Diptera: Tephritidae) infesting Citrus species under laboratory and field-cage conditions

Ceratitis capitata (or medfly) is one of the major pests currently affecting fruit crops in northwestern Argentinian Citrus-producing areas. Medfly populations are sustained in large exotic fruits, such as Citrus paradisi, Citrus aurantium and Citrus sinensis, which are known to hinder the activity of almost all native parasitoid species. Therefore, a feasible approach to controlling medfly involves the use of exotic parasitoids such as Diachasmimorpha longicaudata. In this study, the prediction that parasitoid females would be proficient at finding medfly larvae infesting the Citrus species mentioned earlier was tested. Particularly, the variation in fruit species preference by parasitoid females, the efficacy of the parasitoid to kill medfly and the effect of host density on parasitoid performance were determined. Parasitoids were allowed to forage for 8 h on grapefruits and oranges artificially infested with medfly larvae under controlled (laboratory) and uncontrolled (field cage) environmental conditions. Fruit choice and no-choice tests were performed. Results were assessed by comparing the number of female visits to and ovipositor insertions into the fruit, and parasitoid emergence, parasitism and additional host mortality percentages. Parasitoid preference for visiting larger fruits (sour orange and grapefruit) may be related to the increased fruit surface area. Ovipositional activity on fruit was influenced by the variation of the larval host density per unit of fruit surface. The higher parasitism rates recorded from sweet orange would be mainly a result of both increased host density and fruit physical features. Nevertheless, D. longicaudata showed the capacity to parasitise hosts in all Citrus species tested.     

Parasitoids from Azores (Hymenoptera: Encyrtidae,Pteromalidae, Braconidae): potential use in integrated pest management against Ceratitis capitata (Diptera: Tephritidae)

Two hymenopterous parasitoids, Halticoptera patellana and Toxeumorpha nigricola, were recovered from Mediterranean fruit fly pupae on São Miguel Island, Azores. Both are new records for the Azores, and as Medfly parasitoids. Field-collected Tachinaephagus zealandicus was maintained on Medfly for 10 generations, but if it has potential as a biocontrol agent remains an open question.     

Phloxine B effect on immature stages of the Mediterranean fruit fly,Ceratitis capitata (Diptera: Tephritidae) (Wiedemann)

A laboratory bioassay was developed to determine both the chemical toxicity and the phototoxicity of the xanthene dye, phloxine B (D&C Red No 28), to the immature stages of the Mediterranean fruit fly, Certitis capitata (Wiedemann). An additional goal was to find out which main tissues are affected first. A low, but significant, level of toxicity was observed when the insects were maintained in the dark: at the point of adult ecdysis, the LC50 was 11.03 mM. As expected, after 8-h exposure of late larva III to light, a high level of mortality was produced (LC50 at ecdysis: 0.45 mM) as a dose-dependent function of dye concentration. At sublethal concentrations of the dye, the surviving insects showed a number of physiological abnormalities. Phloxine B appeared to mainly affect the larval longitudinal muscles as well as the abdominal muscles of ecdysing adults, giving rise to abnormal puparia and failed adult ecdysis, respectively. Moreover, a significant phloxine B-dependent delay in the jumping of surviving larvae for dispersal was documented. This could be attributed to a delay in attaining a threshold weight for jumping and/or to abnormalities in neuromuscular coordination, thus reinforcing the idea of pleiotropic effects of the dye.     

Interactions Between Augmentatively Released Diachasmimorpha longicaudata (Hymenoptera: Braconidae) and a Complex of Opiine Parasitoids in a Commercial Guava Orchard

A study was conducted to determine the eVect of augmentatively releasing mass-reared Diachasmimorpha longicaudata (Ashmead) on a complex of four co-existing parasitoid species which attack the oriental fruit fly, Bactrocera dorsalis (Hendel). The species belonging to this complex are the egg-pupal parasitoid, Biosteres arisanus (Sonan) and the larval-pupal parasitoids, Biosteres vandenboschi (Fullaway), D. longicaudata and Psyttalia incisi (Silvestri). The study site was a 160-ha commercial orchard of common guava, Psidium guajava L. (cv. Beaumont) located on Kauai island. One year before the release of D. longicaudata, B. arisanus was the dominant parasitoid, accounting for 91.1% of the parasitoids recovered. Despite releases of large numbers of D. longicaudata (600000-800 000 parasitized puparia/ week), B. arisanus continued to account for 90% of all parasitoids recovered from the oriental fruit fly. The larval parasitoid P. incisi may have been reduced as a result of D. longicaudata releases. D. longicaudata was significantly more abundant in over-ripe and rotting fruits compared with freshly fallen fruits. However, no increase in the overall percentage parasitism was observed in any fruit ripeness category. B. arisanus was eY cient at colonizing hosts when fruit fly densities and fruit abundance were relatively low in the orchard. The implications for future augmentative release programmes with D. longicaudata are discussed.     

Determination of host status of citrus fruits against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Abstract  The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) is a pest of citrus in parts of Western Australia. Three citrus cultivars: Valencia oranges, Eureka lemons and Imperial mandarins, as well as non-citrus control fruits, were examined for attractiveness and suitability to Medfly in the field and in the laboratory using choice and no-choice experiments. Oranges were more susceptible to Medfly than mandarins and lemons. Punctures in the skin had a significant impact on the degree of infestation in both citrus and non-citrus control fruit. Artificial infestation and larval survivorship were used to investigate the suitability of each cultivar to Medfly under laboratory conditions. Oranges and mandarins were suitable for the development of Medfly, but lemons were a poor host. When each cultivar was in season, field cage trials demonstrated that infestation occurred in oranges and mandarins but not in lemons.     

Reproductive biology of Fopius arisanus (Hymenoptera: Braconidae) on Ceratitis capitata and Anastrepha spp. (Diptera: Tephritidae)

The reproduction of the solitary endoparasitoid Fopius arisanus (Sonan) (Hymenoptera: Braconidae) in Anastrepha ludens (Loew), Anastrepha obliqua (Macquart), and Anastrepha serpentina (Wiedemann) was compared with that using Ceratitis capitata (Wiedemann), being the host in which it had been reared previously. Eggs of different ages (<4 h old, 1, 2, and 3 days old for Anastrepha spp., and ⩽4 h, 1 and 2 days old for C. capitata) of each host species were placed in pieces of papaya, exposed to parasitism for 24 h and then reared through to the adult stage. Host species had a marked effect on parasitoid reproduction with consistently higher parasitoid emergence from C. capitata, whereas emergence from A. obliqua was negligible and this host was not studied further. Host age did not significantly affect parasitoid emergence from C. capitata whereas parasitism of A. ludens and A. serpentina was significantly greater in eggs exposed at 3 days old than those exposed at younger ages. Adult parasitoid sex ratio was male biased in all cases. Despite significant differences in host developmental time, host species did not affect parasitoid developmental time. Parasitoid life expectancy at emergence was reduced by >60% for parasitoids that emerged from A. ludens compared to those that emerged from A. serpentina or C. capitata. The reproduction of parasitoid progeny was highest in parasitoids that emerged from and reproduced on C. capitata and lowest for parasitoids reproducing on A. ludens. Parasitoids that emerged from A. ludens were often deformed, but were larger than those that emerged from A. serpentina. Parasitoids that emerged from C. capitata were smaller than those from Anastrepha spp. We conclude that F. arisanus is capable of sustained reproduction in C. capitata and A. serpentina and merits further study as an agent for the control of these fruit flies.     

Hosts of Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) from Broome and the Broome Peninsula, Western Australia

Abstract  In the Kimberley region of Western Australia, Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is only established at Broome. From 1998 to 2001 extensive fruit sampling was carried out at Broome during a trial investigating the eradication of medfly from the Kimberley using the sterile insect technique. Fruit was collected from 82 native and introduced plants growing in and surrounding the town of Broome and held for emergence of medfly. Eighteen plants, including the native tree Terminalia petiolaris , were found to be medfly hosts . On the basis of abundance, fruiting phenology and host suitability, eight species (kumquat Fortunella japonica , mango Magnifera indica , Barbados cherry Malpighia glabra , orange jessamine Murraya paniculata , guava Psidium guajava , Pacific almond Terminalia catapa , blackberry tree Terminalia petiolaris and yellow oleander Thevetia peruviana ) were the most important hosts ensuring medfly survival and population growth. Despite medfly being reared from T. petiolaris , it is likely that medfly can only maintain populations in areas close to human habitation, and eradication from these areas would lead to eradication from the whole Kimberley region.     

Response of Three Hymenopteran Parasitoids Introduced for Fruit Fly Control to a Gall-Forming Tephritid,Procecidochares alani(Diptera: Tephritidae)

The response of three larval–pupal parasitoids,Diachasmimorpha longicaudata(Ashmead),Diachasmimorpha tryoni(Cameron), andTetrastichus giffardianusSilvestri, to the Hamakua pamakani gall fly,Procecidochares alaniL., was determined in the laboratory. We also observed responses of these parasitoids to their normal rearing hosts,Bactrocera dorsalis(Hendel) andCeratitis capitata(Weidemann).D. tryonilanded on pamakani galls or on dishes containingP. alanilarvae as frequently as on dishes containingC. capitata.In contrast,D. longicaudataonly rarely landed on the galls.D. tryoniandD. longicaudataoviposited in galls in fewer than 1% of our observations.D. longicaudataprobedP. alanilarvae as frequently asB. dorsalislarvae, but no parasitoid offspring were observed.D. tryonioviposited more frequently inC. capitatathanP. alani.NoD. tryonideveloped inP. alanilarvae.T. giffardianuslanded on pamakani galls andP. alanilarvae more frequently than any other host substrate. In contrast,T. giffardianusentered galls with artificially opened windows one time in 10 observations. We observed 12% parasitism ofP. alanilarvae dissected from the galls and 20% of parasitismP. alaniin the windowed galls. We discuss the implications of our results for future augmentative or classical biological control studies.     

Fine structure and morphogenesis of the micropylar apparatus in the medfly Ceratitis capitata (Wiedemann) (Diptera : Tephritidae)

The micropylar apparatus (MA) in Ceratitis capitata (Diptera : Tephritidae) is a cone-like protrusion, 18 μm long, at the anterior pole of the egg, and exhibits about 40 follicle cell imprints externally. It consists of chorionic and vitelline membrane parts. The first contains at least a 3 μm wide micropylar canal; the tip of the MA is covered by a “tuft” and includes the micropyle, i.e. the entrance of the micropylar canal. The canal leads to the vitelline membrane part, where it forms a pocket. The sperm enters the oocyte by passing through the micropyle-micropylar canal-pocket route.At least 40 follicle cells participate in the formation of the micropylar apparatus. Two of these form 2 projections, which are tightly connected, and serve as a template for the formation of the canal and the pocket. Throughout their length, both projections have microtubules in parallel arrangement. During oogenesis, the remaining micropylar cells secrete the successive eggshell layers, i.e. the vitelline membrane, the wax layer, the innermost chorionic layer, the endochorion, and the exochorion. Towards the end of oogenesis, the 2 projections degenerate, and the canal becomes available for sperm passage.     

Pupal development of Ceratitis capitata (Diptera: Tephritidae) and Diachasmimorpha longicaudata (Hymenoptera: Braconidae) at different moisture values in four soil types

This study aimed to evaluate adult emergence and duration of the pupal stage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and emergence of the fruit fly parasitoid, Diachasmimorpha longicaudata (Ashmead), under different moisture conditions in four soil types, using soil water matric potential. Pupal stage duration in C. capitata was influenced differently for males and females. In females, only soil type affected pupal stage duration, which was longer in a clay soil. In males, pupal stage duration was individually influenced by moisture and soil type, with a reduction in pupal stage duration in a heavy clay soil and in a sandy clay, with longer duration in the clay soil. As matric potential decreased, duration of the pupal stage of C. capitata males increased, regardless of soil type. C. capitata emergence was affected by moisture, regardless of soil type, and was higher in drier soils. The emergence of D. longicaudata adults was individually influenced by soil type and moisture factors, and the number of emerged D. longicaudata adults was three times higher in sandy loam and lower in a heavy clay soil. Always, the number of emerged adults was higher at higher moisture conditions. C. capitata and D. longicaudata pupal development was affected by moisture and soil type, which may facilitate pest sampling and allow release areas for the parasitoid to be defined under field conditions.     

Unexpected segregation ratios from male-linked translocations in the Mediterranean fruitfly,Ceratitis capitata (Diptera: Tephritidae)

Three male-linked translocations were isolated in the Mediterranean fruitfly, Ceratitis capitata (Wiedemann) which showed sex linkage for an autosomal pupal colour marker, white pupa (wp). The wild type allele (wp ^–) was translocated to the male-determining chromosome. Males emerge from wild type pupae (brown) and females from white pupac. These lines will be used to develop an automatic sexing system.During maintenance of these lines in large populations it was noted that in two of them there was a significant distortion in the expected 1: 1 segregation ratio for pupal colour and excess white pupae were produced. However, adults did not emerge from a large proportion of these pupae. Using known numbers of 1st instar larvae from the three lines, the distortion was further studied and the effect confirmed. To account for this pupal colour segregation distortion it was assumed that certain duplication/deficiency zygotes survive to the late pupal stage. These zygotes have a deficiency for the wild type allele, therefore the normally recessive mutant allele wp could be expressed (pseudo-dominance).The overall fitness of the three lines was calculated, and their suitability for the genetic sexing of large populations is discussed.     

Issues Concerning the Eradication or Establishment and Biological Control of the Mediterranean Fruit Fly,Ceratitis capitata(Wiedemann) (Diptera: Tephritidae), in California

Classical biological control is suggested as a tool worth developing now for possible future use in the integrated pest management of the Mediterranean fruit fly (Medfly),Ceratitis capitata(Wiedemann), in California. Three factors that impact broadly on developing and implementing such a biological control program are: (1) the question of Medfly establishment, (2) quarantine considerations, and (3) agricultural and urban concerns. Each of these factors and their combined effects must be considered when discussing biological control of Medfly in California as shaped by historical perspectives on Medfly invasions, methods of Medfly eradication, and past biological control efforts against Medfly. We believe that biological control research should play a foundational role in any future Medfly management programs in California. Development of biological control should involve life history studies of Medfly and its natural enemies in their area of endemicity in sub-Saharan, southeast Africa. Medfly has been studied and should continue to be studied in areas it has invaded, because information derived from such studies provides insights into the potential distribution, abundance, and impact of Medfly populations in California. A plan for a biological research program on Medfly and its relatives and a biological control strategy are presented.