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.     

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.     

Evaluation of the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) reared on a genetic sexing strain of Ceratitis capitata (Wied.) (Diptera: Tephritidae)

If a genetic sexing strain of Ceratitis capitata could be used to produce sterile males and to rear parasitoids at the same time, significant amount of resources could be saved in comparison with the production of these two biological agents separately. We studied here the major biological parameters comparing two strains of the parasitoid Diachasmimorpha longicaudata, one of them reared on a wild type strain of C. capitata: DL(+), and the other on a genetic sexing strain of C. capitata: DL(sw). The mean longevity, fecundity, and sexual proportion of their respective offspring showed no significant difference. Moreover, no difference was observed in population parameters such as mean generation time, net reproductive rate, finite rate of increase, doubling time, and intrinsic rate of increase. The biological parameters of other artificially reared parasitoids in the Tephritidae family are reviewed, and the conclusion is reached that, rearing the parasitoid on this particular genetic sexing strain of C. capitata does not produce any negative effect on the biological parameters studied.     

桔小实蝇及其寄生性天敌——前裂长管茧蜂饲养方法

系统介绍了桔小实蝇Bactrocera dorsalis（Hendel）室内饲养的设备、步骤、技术要点、人工饲料配方及环境要求,并以桔小实蝇为寄主,实现了桔小实蝇幼虫一蛹期寄生性天敌前裂长管茧蜂Diachasmimorpha longicaudata（Ashmead）的室内大量繁殖,为进一步利用该蜂防治桔小实蝇打下了良好的基础。     

Abiotic factors affecting Diachasmimorpha longicaudata (Hymenoptera: Braconidae) activity as a natural enemy of Ceratitis capitata (Diptera: Tephritidae) under semi‐natural conditions in the Mediterranean region

The larval–pupal endoparasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) is currently the most commonly employed biological control agent against Tephritid fruit flies in the Americas. However, this parasitoid remains largely ignored and is not used in many regions, including the Mediterranean Basin. In this study, the potential of D. longicaudata as a biocontrol agent against the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae) was addressed in an area of eastern Spain (the Valencian community). The parasitic activity of parasitoids and the effects of climatic conditions were evaluated throughout a 1‐year period in field‐cage experiments in which parasitoids were confined with apples artificially infested with medfly larvae. The following parameters were calculated and related statistically to several environmental conditions: the parasitism rate, the induced mortality and progeny sex ratio. The results show that D. longicaudata is able to parasitize medfly larvae throughout the year under semi‐natural conditions. Important fluctuations in the parasitism rate (from almost zero to 42%) and the induced mortality (from 6% to 80%) were partially influenced by climatic conditions. The parasitism rate increased with mean temperature and decreased with mean relative humidity, while the induced mortality decreased with minimum relative humidity. The optimal climatic conditions for the activity of the parasitoid were a mean temperature of 16–24°C combined with a relative humidity of 45%–60%. Overall, these results suggest that reduction in the medfly population due to D. longicaudata activity is feasible and provide information about the optimal time period for parasitoid release in the field. In conclusion, D. longicaudata has a significant potential to control C. capitata in the Mediterranean region.     

First record of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) attacking Toxotrypana curvicauda Gerstaecker (Diptera: Tephritidae)

A new host record is reported for the braconid wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), parasitizing papaya fruit fly larvae Toxotrypana curvicauda Gerstaecker (Diptera: Tephritidae) in México.     

前裂长管茧蜂个体发育研究

前裂长管茧蜂Diachasmimorpha longicaudata（Ashmead）是许多双翅目实蝇类害虫的重要寄生性天敌。在实验室条件下,以桔小实蝇Bactrocera dorsalis（Hendel）为繁育寄主,系统观测了前裂长管茧蜂个体发育过程中各虫态的特征及其相应的发育历期。观察结果表明,前裂长管茧蜂整个生活史由卵、幼虫、蛹及成虫四个阶段组成。其幼虫可划分为四个龄期,一龄幼虫具几质丁的坚硬头壳和镰刀状的颚,形态特征与行为习性与二、三、四龄幼虫完全不同。前裂长管茧蜂约需20天完成世代发育。卵、一龄幼虫、二龄幼虫、三龄幼虫及四龄幼虫的历期依次为1．91、2．02、1．75、2．04和2．31d;蛹的历期介于8～10d,雌性个体发育时间长于雄性。前裂长管茧蜂通常比未被寄生的寄主迟3～5d羽化,雌、雄蜂在羽化后即能交配、产卵,被寄生的桔小实蝇幼虫体表上会留下明显的深褐色产卵孔,寄主化蛹后产卵孔仍保留在其蛹壳上。     

Spermatogenesis in the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

The study of spermatogenesis in Hymenoptera is limited to few taxa due to limitations to access the material in the right stage for analysis. The information available up to now states that the gametogenesis in males involves a modified meiosis, similar to mitosis. This is due to the haplodiploid sex determination system present in the order, where females are diploid and males are haploid. In the present work, we examined the spermatogenesis process in the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). We performed squash preparations from testes of individuals from the third larval instar until the adult stage. Some cytological traits, such as the presence of a monopolar spindle, were analysed in detail by means of histological semi‐thin sections. The spermatogenesis in this species comprises an abortive first division with the formation of an anucleated cytoplasmic bud and a nucleated cell, and an equal second division of the nucleated cell, leading to the generation of two mature spermatozoa. The results presented herein provide more information about the process of spermatogenesis in Hymenoptera, which has not been studied in depth in parasitic species.     

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.     

X-ray doses to safely release the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) reared on Anastrepha fraterculus larvae (Diptera: Tephritidae)

Diachasmimorpha longicaudata is a koinobiont larval parasitoid that is currently used to control fruit flies of the genera Anastrepha, Ceratitis and Bactrocera. In the rearing process, a fraction of the host larvae that are exposed to parasitoids escape from parasitism and develop into viable and fertile flies. This creates the need to eliminate emerging flies before the parasitoids are shipped for release, increasing costs due to additional handling steps. Exposure of fly eggs or larvae to gamma-irradiation before they are parasitised has been used to reproductively sterilise hosts, or even inhibit their emergence. Our aim was to determine whether X-ray radiation applied to Anastrepha fraterculus third instar larvae before they are exposed to parasitoids, inhibits fly emergence in non-parasitised larvae without affecting the performance of the parasitoids that emerge from parasitised larvae. Three X-ray doses: 6250.2 R, 8333.6 R and 10417 R (equivalent to 60, 80 and 100 Gy, respectively) and one γ-ray dose (100 Gy) were tested. Fly emergence decreased with increasing doses of radiation, showing null values for the higher X-ray dose and the dose of 100 Gy. Irradiation showed either no impact or a positive effect on parasitism rate and fecundity. Sex rate was biased towards females in almost every dose. We conclude that the two types of radiation evaluated here were equally effective in suppressing fly emergence with no detrimental effects on the biological quality of the produced parasitoids. X-rays offer an alternative method of irradiation than the conventional radiation source, i.e. γ-rays. These results represent a significant improvement in the development of a biological control programme against A. fraterculus.     

A compound produced by fruigivorous Tephritidae (Diptera) larvae promotes oviposition behavior by the biological control agent Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Tephritid fruit fly parasitoids use fruit-derived chemical cues and the vibrations that result from larval movements to locate hosts sequestered inside fruit. However, compounds produced by the larvae themselves have not been previously described nor their significance to parasitoid foraging determined. We collected the volatiles from four species of tropical and subtropical Tephritidae: Anastrepha suspensa (Loew), Bactrocera dorsalis Hendel, Bactrocera cucurbitae Coquillett, and Ceratitis capitata (Wiedemann), representing two subfamilies (Dacinae and Trypetinae). Para-ethylacetophenone, an analog of a known tephritid parasitoid attractant, was a major constituent of all four, and was not associated with larvae of another acalypterate fly, Drosophila melanogaster Meigen, or with the calypterate Musca domestica L. It also was present in volatiles from whole, A. suspensa infested fruits of Eugenia uniflora (L.). Para-ethylacetophenone was not necessarily produced as a direct consequence of fruit consumption because it also was detected from larvae that developed in two artificial diets and in spent diets subsequent to larval development. Sensillae on both the antennae and ovipositor of the opiine braconid fruit fly parasitoid, Diachasmimorpha longicaudata (Ashmead) responded to the para-ethylacetophenone in larval volatiles and as a synthetic. Although a potential cue to foraging parasitoids, para-ethylacetophenone showed no long range (>1m) attractiveness to the adult female parasitoid, but did stimulate ovipositor-insertion and oviposition into both a natural (fruit) and an artificial (parafilm) substrate. Thus it may prove useful in colonizing and mass-rearing opine fruit fly parasitoids.     

Parasitism on medfly by Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in different guava cultivars

The parasitism efficiency of the Braconidae wasp, Diachasmimorpha longicaudata (Ashmead), was checked on four guava cultivars (Paluma, Sassaoca, Pedro Sato and Kumagai) infested with larvae of medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Five blocks of eight fruits, each with two fruits of each cultivar, were put inside C. capitata adult cages, during 2h for oviposition, and a week later, when the larvae inside guavas were developed, the fruits were exposed to parasitoids for 24h. The mean fruit weight, larvae mortality, number of pupae, percentage of medfly and parasitoid emergence were evaluated. There was not statistical difference among cultivars to weight, larvae mortality, number of pupae e emergence of medfly. The percentage of parasitism was higher in Pedro Sato cultivar (19.8%) compared with Kumagai cultivar (2.9%), but it was statistically similar to the other cultivars.     

Acrosome formation in Ceratitis capitata (Diptera, Tephritidae)

The stages of morphogenesis of the acrosome of Ceratitis capitata are well defined. This organelle is formed by the Golgi complex and, as it matures, takes up a position laterally in relation to the anterior region of the sperm nucleus. An interstitial membrane marks the area of contact between nucleus and acrosome in the spermatid, and is found even in mature sperm cells. The acrosome contains hydrolytic enzymes, as detected by acid phosphatase reaction.     

Toxicity of imidacloprid-treated spheres to Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) and its parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in the laboratory

No-choice cage tests were used to study the toxicity of imidacloprid-treated spheres to Caribbean fruit fly, Anastrepha suspensa (Loew), and its associated parasitoid, Diachasmimorpha longicaudata (Ashmead), in the laboratory. Three imidacloprid sphere treatments (2, 4, and 8% active ingredient [AI] Provado 1.6 F) and an untreated control sphere (no toxicant) were evaluated against A. suspensa. Throughout the observation period (2-72 h), all concentrations of imidacloprid-treated spheres killed significantly more A. suspensa compared with control spheres. After 4 h of exposure to imidacloprid-treated spheres, significantly more A. suspensa were killed on spheres treated with 8% compared with 2% (AI). At 48 and 72 h, there were no significant differences in the mean number of A. suspensa killed at 2, 4, and 8% (AI), potentially indicating that a period of 24 h was sufficient for flies to ingest a lethal dose of the pesticide. Overall, significantly more A. suspensa males were killed after 72 h of exposure to imidacloprid-treated spheres compared with females. For D. longicaudata, only two imidacloprid sphere treatments, 2 and 4% (AI), and an untreated sphere (control) were evaluated for mortality in cage tests. There were no significant differences in mortality of D. longicaudata between the 2 and 4% (AI) imidacloprid-treated spheres. Both rates killed significantly more D. longicaudata compared with the control. However, after 24, 48, and 72 h of exposure to imidacloprid-treated spheres, significantly more D. longicaudata were killed in cages containing 4% compared with 2% (AI) and untreated control spheres. The study demonstrates the potential use of imidacloprid-treated spheres for control of A. suspensa in areas where it may be difficult to apply broad-spectrum insecticides.     

Protein polymorphism in natural populations of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in Thailand

Diachasmimorpha longicaudata (Ashmead) is a larval parasitoid of tephritid flies and is widely used as a classical biological control agent. We have used allozyme electrophoresis to evaluate the genetic relationships of six populations of D. longicaudata in Thailand. Twelve loci were examined of which 11 were polymorphic in at least some populations, especially that of Nakornratchasima. We observed a complete lack of heterozygotes for seven of the 10 polymorphic loci in the Nakornratchisima female population, and a significant deficiency of heterozygotes at a further two loci. We discuss possible hypotheses for these findings in light of the haplo-diploid sex determination system of these wasps. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intrinsic competition between Diachasmimorpha longicaudata and three native species of parasitoids (Hymenoptera: Braconidae: Opiinae) of Anastrepha (Diptera: Tephritidae) fruit flies under laboratory conditions

The effect of intrinsic competition between the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) and the native species Doryctobracon crawfordi (Viereck), Utetes anastrephae (Viereck) and Opius hirtus (Fischer) (all Braconidae: Opiinae) was studied under laboratory conditions. Each native species and D. longicaudata acted as both a resident and an invader, and all species were introduced to the host simultaneously. Diachasmimorpha longicaudata was found to be the most competitive species because it achieved the highest parasitism percentage under all the experimental conditions, but it was also negatively affected by the presence and parasitic activity of the native parasitoids. Utetes anastrephae was the only species that maintained its parasitic rate when all species attacked the available hosts simultaneously. The emergence probability of a female D. longicaudata was positively associated with the increase in the number of scars on the cuticle of the host pupa, but this association was not observed for the native species. It was concluded that D. longicaudata is an intrinsic competitor that is superior to D. crawfordi, U. anastrephae and O. hirtus, whether acting as a resident or an invader, producing a female-biased sex ratio in all the evaluation conditions. Utetes anastrephae was the native species that was least affected by the competitive presence of D. longicaudata, which suggests that it could be used as a complementary biological control agent for Anastrepha fruit flies.     

Choriogenesis in the medfly Ceratitis capitata (Wiedermann) (Diptera : Tephritidae)

Four chorionic stages (11, 12, 13, 14) can be discerned in the medfly Ceratitis capitata (Diptera : Tephritidae) by light microscope. More detailed staging (stages 11A, 11B, 12A, 12B, 12C, 13A, 13B, 13C, 14A and 14B) is possible only by electron microscope. Throughout these stages, the first chorionic layer (wax layer) is formed at stage 11A, followed by the formation of the innermost chorionic layer (stage 12A), the inner endochorion, the pillars and the cavities of the first trabecular layer (stage 12), creation of the second trabecular layer and the chorionic network (stage 13), and finally the secretion of the exochorionic layers (stage 14). Pulse-chase autoradiography has revealed that the follicle cells are responsible for the synthesis of all proteinaceous layers. No extensive regional complexity is observed besides the existence of the micropylar apparatus and aeropyles in the anterior pole. Biochemical analysis has revealed several eggshell proteins and their stage-specific synthesis: two intermediate molecular-weight proteins are the major chorion proteins; in addition, there are 2 more groups comprising 6 proteins, which might be characteristic for the different chorion layers as can be deduced by their stage-electrophoretic pattern.     

Pathogenicity of Metarhizium anisopliae for Ceratitis capitata (Wied.) (Diptera: Tephritidae) in soil with different pesticides

This research intended to investigate if the presence of pesticides in the soil could affect the pathogenicity of Metarhizium anisopliae Metsch. (Sorokin) for Ceratitis capitata (Wied.) and assess the effect of conidia application as suspension or dry conidia. The fungicides chlorothalonyl and tebuconazol, the acaricide abamectin, the insecticide trichlorfon, and the herbicide ametrin were applied at the manufacturer-recommended doses. Soil samples were placed in glass flasks and were given the fungus as conidial suspension or dry. After pesticide application, 20 3rd-instar larvae were placed in the soil. The flasks were sealed with voile fabric and incubated at 27 +/- 0.5 masculineC for nine days, until adult emergence; incubation continued for four more days at room temperature. The total insect survival was significantly affected and pathogenic activity was detected from the pupa stage on. Pupa survival was reduced (P<0.05); the same occurred during the adult phase. No effect was observed at the larval stage. The pesticides applied to the soil affected the activity of M. anisopliae slightly: only in the dry conidia assay the fungicides chlorothalonyl and tebuconazole reduced (86.2% and 82.5%, respectively) the survival period of C. capitata compared to the control (95.0%). The techniques used for conidia application did not influence the total insect survival rate, but conidial suspension applied on soil surface reduced survival during the pupae and adult phases.