Laura P. Bezdjian

Host Preference by Diachasmimorpha longicaudata (Hymneoptera: Braconidae) Reared on Larvae of Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae)

ABSTRACT The preferences of Diachasmimorpha longicaudata (Ashmead) for larvae of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) were evaluated under laboratory conditions in no-choice and dual-choice tests, based on percent parasitism, proportion of emerged parasitoids, proportion of female offspring, and number of parasitoid female visits to and ovipositor probes on the artificial oviposition device as different measures of host preference. In no-choice tests D. longicaudata females did not demonstrate a significant preference between C. capitata and A. fraterculus larvae. Nevertheless, D. longicaudata females showed a strong preference for A. fraterculus larvae in dual-choice test. Although female biased parasitoid progeny resulted in all assays, significantly more D. longicaudata female offspring emerged from A. fraterculus pupae than from C. capitata pupae. Thus, this study confirmed that both C. capitata and A. fraterculus are appropriate host for rearing D. longicaudata, but also provided evidence that female parasitoid progeny yield can be substantially improved by using A. fraterculus larvae as the host instead of C. capitata larvae.

Effect of Exposure Time and Ratio of Hosts to Female Parasitoids on Offspring Production of Diachasmimorpha longicaudata (Hymneoptera: Braconidae) Reared on Anastrepha fraterculus (Diptera: Tephritidae) Larvae

ABSTRACT Diachasmimorpha longicaudata (Ashmead) is a larval-prepupal endoparasitoid of tephritid fruit fly pests in tropical and subtropical countries. Because citrus-growing areas of northern Argentina are the most affected by Anastrepha fraterculus (Wiedemann), D. longicaudata presents as a potential candidate for augmentative releases against it. Within this context, parasitoid rearing must be focused on offspring yield optimization in order to sustain a successful massrearing process. Hence, the best ratio of A. fraterculus larva to female parasitoids and the best exposure time for achieving the greatest parasitoid yield with the highest proportion of female progeny were determined under laboratory conditions in the present study. The effect of superparasitism on the percentage of D. longicaudata emergence was also assessed. Third-instars of A. fraterculus were exposed for 30, 60, 90, and 120 min to 30 mated, 5–7 d-old parasitoid females at host/parasitoid ratios of 2:1, 4:1, 6:1, 8:1, and 10:1. Results showed that a low ratio of hosts exposed to parasitoids for a short time was essential to achieve parasitoid emergence rates exceeding 70%, and to achieve a ♀:♂ sex ratio of at least 61:39. Increasing both the ratio of host larvae to parasitoid further than 4:1 and the exposure time of D. longicaudata to hosts beyond 30 min did not significantly enhance overall parasitoid progeny yield. There was a significant negative correlation between the number of parasitoid 1st instars recorded per dissected host pupa and the percentage of parasitoid emergence. Conversely, a significant positive correlation was found between superparsitism and additional host mortality. Although a female-biased sex ratio resulted in all treatments, the greater parasitoid female progeny proportions were found in association with the higher levels of superparasitism.

Natural Ocurrence of Hymenopterous Parasitoids Associated with Anastrepha fraterculus (Diptera: Tephritidae) in Myrtaceae Species in Entre Rios, Northeastern Argentina

Abstract Parasitoids of Anastrepha fraterculus (Wiedemann) were monitored on ripe fruit of 3 native and 1 exotic, wild Myrtaceae species in the Province of Entre Rios, NE Argentina, between Jan and Mar 1993 and 1994 with the aim of identifying indigenous parasitoid species and determining natural parasitization rates and fruit infestation levels. The fruit species surveyed were Psidium guajava L. (common guava), Feijoa sellowiana (O. Berg) O. Berg (feijoa), Eugenia uniflora L. (Surinam cherry), and Myrcianthes pungens (Berg) Legrand (mato). Altogether 2,186 tephritid puparia were obtained, 95% of which were A. fraterculus and 5% of which were Ceratitis capitata (Wiedemann). Of 1,667 adult insects that emerged from these puparia, 1,378 were A. fraterculus, 89 C. capitata, and 200 larval-pupal parasitoids, representing 4 species of 2 Hymenoptera families: Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), Utetes anastrephae (Viereck) (all Braconidae, Opiinae), and Aganaspis pelleranoi (Brèthes) (Figitidae, Eucoilinae). All these parasitoid species are new reports for Entre Rios. Moreover, these records represent the southernmost natural distribution range in the Americas for these species. Doryctobracon areolatus and A. pelleranoi were recovered from all of the Myrtaceae species sampled, and they were the most abundant parasitoid species. Infestation patterns by A. fraterculus in mato, Surinam cherry, guava, and feijoa varied from 15.2 to 41.8, 21.3 to 49.4, 34.1 to 109.2, and 78.9 to 140.6 larvae per kg of fruit, respectively. Highest levels of parasitism were recorded in P. guajava, whereas M. pungens had the lowest parasitization rates. However, overall mean parasitism levels (i.e., considering all parasitoid species) did not appear to have great differences when comparing Myrtaceae species, collection sites, and years. The relative abundance and parasitization rates data of the recovered parasitoids in the 4 Myrtaceae species suggest some degree of host plant preference by U. anastrephae and D. brasiliensis.

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

Abstract 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.

Offspring Production in Response to Host Exposure Times in Diachasmimorpha longicaudata (Hymenoptera: Braconidae), Reared on the Genetic Sexing Strain Vienna 8 of Ceratitis capitata (Diptera: Tephritidae)

ABSTRACT The objective of the present study was to assess the effect of different times of exposure to the host on parasitoid emergence rate, parasitoid progeny sex ratio, and on host mortality, as a step toward the development of an efficient mass-rearing system for the braconid Diachasmimorpha longicaudata (Ashmead) on larvae of the VIENNA 8 Temperature Sensitive Lethal Ceratitis capitata (Wiedemann) strain. The role of host-rearing substrate cues in stimulating the host-searching behavior of parasitoid females was also evaluated. Three exposure times (40, 60, and 120 min) were tested. One hundred 7 d-old host larvae were exposed to 25 female parasitoids per treatment. Larvae mixed with wheat-based rearing medium and larvae without medium were used in each test. A second set of treatments with the same method described above was conducted using late third-instars of the C. capitata wild-type strain. These experiments were carried out to assess the quality of the larvae of VIENNA 8 strain in producing D. longicaudata adults by comparing them with the larvae of the wild-type strain. Results indicated that the use of larvae of VIENNA 8 strain on their rearing diet at 40 min exposure time significantly increased overall parasitoid offspring production and decreased the host mortality level. Nevertheless, parasitoid emergence recorded from VIENNA 8 strain was notably lower than that recorded from the wild-type strain. Low parasitoid emergence levels and the prevalence of male-biased progeny recorded in all assays are obstacles to development of a parasitoid mass-rearing system using larvae of VIENNA 8 strain as host. Additional studies focusing on host exposure to parasitoids are needed to verify the effect of host larval quality on the production of D. longicaudata.

A Survey of Hymenopterous Larval-Pupal Parasitoids Associated with Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae) Infesting Wild Guava (Psidium guajava) and Peach (Prunus persica) in the Southernmost Section of the Bolivian Yungas Forest

ABSTRACT Parasitoids of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) infesting wild guava (Psidium guajava L.) and peach (Prunus persica (L.) Batsch) fruits in the southernmost extension of the Bolivian Yungas forest, in the Province of Tarija, were surveyed in Dec (early summer), Feb (mid summer) and Mar (late summer) 1999 and 2000. The abundance patterns and diversity of fruit fly larval-pupal parasitoid species were similar to previously published data for the southern and northern Yungas forests of Argentina. A total of 1,600 guavas and 800 peaches, weighing 57.713 kg and 24.544 kg, respectively, were collected yielding 13,080 tephritid puparia, 78.4% of which were A. fraterculus and 21.6% Ceratitis capitata (Wiedemann). We reared 712 larval-pupal parasitoids of the following species: Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), D. crawfordi (Viereck), Opius bellus Gahan, Utetes anastrephae (Viereck) (all Braconidae, Opiinae), Aganaspis pelleranoi (Brèthes) Odontosema anastrephae Borgmeier, and Lopheucoila anastrephae (Rohwer) (all Figitidae, Eucoilinae). Utetes anastrephae, O. anastrephae, and L. anastrephae are new fruit fly parasitoid reports for Bolivia, as well as O. anastrephae in the South American Yungas forest. A thorough sampling of other C. capitata and Anastrepha host plants, mostly native fruit species, will be necessary in the Yungas forest of Bolivia before further conclusions on abundance and composition of all fruit fly parasitoids can be reached.

Occurrence of Ceratitis capitata and Anastrepha fraterculus (Diptera: Tephritidae) on cultivated, exotic fruit species in the highland valleys of Tucuman in Northwest Argentina.

ABSTRACT Fruits from 6 exotic, cultivated fruit species were collected in the Tafí and Calchaquí valleys between Jan 2000 and Jan 2002 to determine the occurrence of Ceratitis capitata (Wiedemann) and Anastrepha fraterculus (Wiedemann) and the corresponding fruit infestation levels. The valleys are situated in the western semiarid highlands of Tucumán province (NW Argentina) and the altitude ranges from 1,800 to 2,014 m above sea level. The fruit species surveyed were Cydonia oblonga Miller, Malus domestica Borkh., Prunus armeniaca L., P. domestica L., P. persica (L.) Batsch, and Pyrus communis L. (Rosaceae). Out of a total of 2,129 puparia recovered from infested fruit, 2,112 (98.8%) were C. capitata and only 27 (1.2%) A. fraterculus. Ceratitis capitata was recovered from all fruit species and it was the dominant species. Anastrepha fraterculus was only recovered from C. oblonga, P. persica and P. domestica. All Prunus species and P. communis were the host plants that were infested most by C. capitata. The infestation data of C. oblonga, P. communis and M. domestica demonstrated that these 3 fruit species were acceptable host plants for C. capitata in Tucumán. This study provides the first record of both C. capitata and A. fraterculus infesting fruit species in semiarid highland valleys in Tucumán, and it also expands the altitudinal range of distribution of these two tephritid species to 2,014 m within the Tucumán province.

Bionomics of Opius bellus (Hymenoptera: Braconidae), an endoparasitoid of Anastrepha fraterculus (Diptera: Tephritidae) in fruit-growing areas of Northwestern Argentina

Opius bellus is a neotropical larval-prepupal parasitoid known to attack the pestiferous fruit fly, Anastrepha fraterculus. Due to interest in the use of native parasitoids in forthcoming fruit fly biocontrol programmes in Argentina, O. bellus was colonised for the first time using laboratory-reared A. fraterculus larvae. A series of experiments were conducted to (1) best achieve an efficient parasitoid rearing by determining optimal larval host age, host:parasitoid ratio and host exposure time and (2) assess their potential as biological control agents by determining reproductive parameters. The most productive exposure regimen was: 7–9 d-old (early and middle third-instars) A. fraterculus larvae for 4 h at a 4:1 host:parasitoid ratio; this array of factors was sufficient to achieve the highest average adult emergence (48%) and an offspring sex ratio at equitable proportion. Increasing both host:parasitoid ratio further than 4:1 and the host exposure time beyond 4 h did not significantly enhance parasitoid female offspring yield. Females produced eggs for 29.5 ± 1.4 days. At 32 days of age, 50% of the females were still alive. The majority of the progeny were produced by females between 20 and 24 d-old. At 26°C, gross fecundity rate, net reproductive rate, intrinsic rate of increase and mean generation time were 20.7 ± 4.2 offspring/female, 9.6 ± 2.5 females/newborn females, 0.06 ± 0.01 females/female/day and 8.4 ± 0.2 days, respectively. The long lifespan and reproductive parameters suggest that this parasitoid species has suitable attributes for mass-rearing.