Fruit infesting tephritids [Dipt.: Tephritidae] and associated parasitoids in Chiapas, Mexico

Tri-trophic interactions among Fopius arisanus, Tephritid species and host plants suggest apparent competition

When several polyphagous herbivore species share a parasitoid, the tri-trophic interaction networks can be difficult to predict. In addition to direct effects, the parasitoid may influence the herbivore community by mediating indirect interactions among hosts. The plant species can also modulate the parasitoid preference for a specific host. One of the indirect effects is apparent competition, a negative interaction between individuals as a result of the action of shared natural enemies. Here, we focus on the interactions between the parasitoid Fopius arisanus (Braconidae) and two generalist fruit fly pests: Bactrocera dorsalis and Bactrocera zonata (Tephritidae). This parasitoid was introduced into La Réunion in 2003 to control populations of B. zonata and can also interact with B. dorsalis since its invasion in 2017. Our main objective is to characterize the tri-trophic interactions between F. arisanus, fruit fly and host plant species. We developed a long-term field database of fruit collected before and after the parasitoid introduction and after the B. dorsalis invasion in order to compare parasitism rate and fruit fly infestation for the different periods. In laboratory assays, we investigated how the combination of fruit fly species and fruit can influence the preference of F. arisanus. In the field, before the invasion of B. dorsalis, the parasitism rate of F. arisanus was low and had a little impact on the fruit fly infestation rate. After the B. dorsalis invasion, we observed an increase in parasitism rate from 5% to 17%. A bioassay showed that females of F. arisanus could discriminate between eggs of different fruit fly and host plant species. The host plant species preference changed in relation to the fruit fly species inoculated. Field observations and laboratory experiments suggest the possible existence of apparent competition between B. dorsalis and B. zonata via F. arisanus.

Increasing radiation doses in Anastrepha obliqua (Diptera: Tephritidae) larvae improve parasitoid mass-rearing attributes

Doses of 40, 80, 120, and 160 Gy were applied to 5-, 6-, 7-, and 8-day-old Anastrepha obliqua larvae, which were exposed to the Neotropical-native braconids Doryctobracon crawfordi and Utetes anastrephae and the Asian braconid Diachasmimorpha longicaudata. These tests were performed to know the effect of the increase in host radiation on the emergence of the aforementioned parasitoids and the related consequences of oviposition on the host. The study was based on the fact that higher radiation doses may cause a decrease in the host immune activity. There was a direct relationship between the increase in radiation dose and the parasitoid emergence. Both, the weight and the mortality of the host larvae were not affected by radiation. Although the larval weight of the larvae was lower and the mortality was higher in the younger larvae. Both, the number of scars and immature stages per host puparium originated from the younger larvae were lower than those from older larvae. Only U. anastrephae superparasitized more at lower radiation. Superparasitism by D. longicaudata was more frequent at 160 Gy. Qualitative measurements of melanin in the larvae parasitized showed that the levels were lower with increasing radiation. As radiation doses increased, the antagonistic response of the A. obliqua larva was reduced. Host larvae aged 5- and 6-day-old irradiated at 120-160 Gy significantly improve parasitoid emergence. This evidence is relevant for the mass production of the three tested parasitoid species.

Determination of temperature thresholds for the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae), using life cycle simulation modeling: Implications for effective field releases in classical biological control of fruit flies

The braconid parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) is one of the most important natural enemies in classical biological control programs against tephritid fruit flies worldwide. In light of the spread of the invasive fruit fly species, Bactrocera dorsalis in Africa and beyond, there is a need to implement classical biological control. The current study aimed to determine temperature thresholds for D. longicaudata reared on B. dorsalis, using life cycle simulation modeling to guide informed parasitoid releases in Africa. Simulated parameters included thermal requirements, population growth parameters at different temperature requirements, suitable areas for the establishment, and the number of generations per year under projected climatic conditions. The lower thermal threshold for the development was estimated at 10.0°C, with a thermal constant (k) of 333.3-degree days, while the maximum temperature threshold was estimated at 33.69°C. Fecundity was highest at 25°C, with 177.3 eggs per female. Temperature significantly affected the population growth parameters of D. longicaudata, and the maximum value of the intrinsic rate of increase (rm) was 0.145 at 27°C. Results indicate that D. longicaudata could successfully establish in tropical and sub-tropical regions under current and future climatic conditions. However, a slight change in the suitable areas is expected by the year 2050 due to a slight and gradual rise in temperature. Our findings provide important information for further release of this parasitoid in Africa as well as designing pest management strategies to limit the spread and reduce the impact of fruit flies sustainably.

Biological Control of Tephritid Fruit Flies in the Americas and Hawaii: A Review of the Use of Parasitoids and Predators

Simple Summary

Biological control has been the most commonly researched control tactic within fruit fly management programs, and parasitoids have been the main natural enemies used against pestiferous fruit fly species. In view of this fact, it is important to highlight and compile the data on parasitoids with a certain frequency, aiming to facilitate the knowledge of all the researchers. Information regarding the activities of parasitoids and predators on pestiferous fruit flies in the Americas is limited; therefore, this study aimed to compile the diversity of parasitoids and predators associated with tephritid fruit flies, as well as providing the scientific evidence about the use of parasitoids and predators as biological control agents for fruit flies im the Americas and Hawaii.

Abstract

Biological control has been the most commonly researched control tactic within fruit fly management programs. For the first time, a review is carried out covering parasitoids and predators of fruit flies (Tephritidae) from the Americas and Hawaii, presenting the main biological control programs in this region. In this work, 31 species of fruit flies of economic importance are considered in the genera Anastrepha (11), Rhagoletis (14), Bactrocera (4), Ceratitis (1), and Zeugodacus (1). In this study, a total of 79 parasitoid species of fruit flies of economic importance are listed and, from these, 50 are native and 29 are introduced. A total of 56 species of fruit fly predators occur in the Americas and Hawaii.

Host availability affects the interaction between pupal parasitoid Coptera haywardi (Hymenoptera: Diiapridae) and larval-pupal parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

The use of multiple species in biological control programmes is controversial when interactions among them are not fully understood. We determined the response of the pupal parasitoid Coptera haywardi (Oglobin) to different availability of Anastrepha ludens (Loew) pupae previously parasitized or not by larval-pupal Diachasmimorpha longicaudata (Ashmead). The two types of pupae were exposed at different ages and proportions to different numbers of C. haywardi females for 48 h. The performance of C. haywardi adults emerging from parasitized and unparasitized pupae was measured. Coptera haywardi prefers to attack unparasitized A. ludens pupae rather than pupae parasitized by D. longicaudata. However, when the availability of unparasitized pupae was low or the number of foraging females was high, C. haywardi competed against early immature stages of the D. longicaudata, or hyperparasitized, feeding directly on the advanced-immature developmental stages of the early acting species. Adults of C. haywardi emerging as hyperparasitoids were no different in size, fecundity and longevity from those emerging as primary parasitoids. Our data suggest that simultaneous use of these species in augmentative biological control projects may be feasible but should be carefully planned in order to avoid any detrimental effect of its interaction.

First instar larvae morphology of Opiinae (Hymenoptera: Braconidae) parasitoids of Anastrepha (Diptera: Tephritidae) fruit flies. Implications for interspecific competition

The morphology of the first instars of the Opiinae braconids Diachasmimorpha longicaudata, Doryctobracon areolatus, Doryctobracon crawfordi, Utetes anastrephae and Opius hirtus (the first is exotic, and the others are natives to Mexico), parasitoids of Anastrepha fruit flies, are described and compared. The possible implications on interspecific competition among these species are discussed. The most significant adaptations found were: (1) the mouth apparatus, where the large mandibles and fang-shaped maxillary lobes present in D. longicaudata and U. anastrephae larvae were absent in O. hirtus, D. areolatus and D. crawfordi larvae, and (2) the degree of mobility for exploration and escape, such as the lateral and caudal appendages that were only present in D. longicaudata (ventrolateral appendages in the base of the head capsule), U. anastrephae (caudal lobe with two appendages) and D. areolatus (caudal lobe with a round apex with a globular shape). The first instar larvae of the species D. longicaudata show morphological adaptations that apparently confer competitive advantages against the larvae of D. areolatus, D. crawfordi and O. hirtus. However, the first instar larvae of U. anastrephae show larger mandibles, an adaptation that could enable this species to resist competition from D. longicaudata.

The current and future potential geographic range of West Indian fruit fly, Anastrepha obliqua (Diptera: Tephritidae)

The West Indian fruit fly, Anastrepha obliqua (Macquart), is one of the most important pests throughout the Americas. CLIMEX 3.0 and ArcGIS 9.3 were used to model the current and future potential geographical distribution of this pest. Under current climatic conditions, A. obliqua is predicted to be able to establish throughout much of the tropics and subtropics, including not only North and South America, where it has been reported, but also southern Asia, northeastern Australia and Sub-Saharan Africa. The main factors limiting the pest's range expansion may be cold stress. Climate change expands the potential distribution of A. obliqua poleward as cold stress boundaries recede, but the predicted distribution in northwestern Australia and northern parts of Sub-Saharan Africa will decrease because of heat stress. Considering the widely suitable range for A. obliqua globally and in China, enhanced quarantine and monitoring measures should be implemented in areas that are projected to be suitable for the establishment of the pest under current and future climatic conditions.

Parasitoids of Queensland Fruit Fly Bactrocera tryoni in Australia and Prospects for Improved Biological Control

This review draws together available information on the biology, methods for study, and culturing of hymenopteran parasitoids of the Queensland fruit fly, Bactrocera tryoni, and assesses prospects for improving biological control of this serious pest. Augmentative release of the native and naturalised Australian parasitoids, especially the braconid Diachasmimorpha tryoni, may result in better management of B. tryoni in some parts of Australia. Mass releases are an especially attractive option for areas of inland eastern Australia around the Fruit Fly Exclusion Zone that produces B. tryoni-free fruits for export. Diachasmimorpha tryoni has been successful in other locations such as Hawaii for the biological control of other fruit fly species. Biological control could contribute to local eradication of isolated outbreaks and more general suppression and/or eradication of the B. tryoni population in endemic areas. Combining biological control with the use of sterile insect technique offers scope for synergy because the former is most effective at high pest densities and the latter most economical when the pest becomes scarce. Recommendations are made on methods for culturing and study of four B. tryoni parasitoids present in Australia along with research priorities for optimising augmentative biological control of B. tryoni.

First record of Calliephialtes sittenfeldae associated with the tephritid fruit fly Anastrepha spatulata in Mexico

This paper reports for the first time an ichneumonid parasitoid Calliephialtes sittenfeldae Gauld Ugalde-Gómez et Hanson (Hymenoptera: Ichneumonidae) associated with a dipteran host Anastrepha spatulata Stone (Diptera: Tephritidae), recovered from fruit of Schoepfia schreberi (Santalales: Olacaceae) in central Veracruz, Mexico. Large numbers of this parasitoid were collected and reared from its fruit fly host in three localities of Veracruz, Mexico. Some observations of its biology are also reported. This is a first record of C. sittenfeldae from Mexico, and the first record of this parasitoid species, its insect host, and the host plant. The male of this species is described and illustrated for the first time.

Effect of larval host food substrate on egg load dynamics, egg size and adult female size in four species of braconid fruit fly (Diptera: Tephritidae) parasitoids

Life history theory predicts that individuals will allocate resources to different traits so as to maximize overall fitness. Because conditions experienced during early development can have strong downstream effects on adult phenotype and fitness, we investigated how four species of synovigenic, larval-pupal parasitoids that vary sharply in their degree of specialization (niche breadth) and life history (Diachasmimorpha longicaudata, Doryctobracon crawfordi, Opius hirtus and Utetes anastrephae), allocate resources acquired during the larval stage towards adult reproduction. Parasitoid larvae developed in a single host species reared on four different substrates that differed in quality. We measured parasitoid egg load at the moment of emergence and at 24 h, egg numbers over time, egg size, and also adult size. We predicted that across species the most specialized would have a lower capacity to respond to changes in host substrate quality than wasps with a broad host range, and that within species, females that emerged from hosts that developed in better quality substrates would have the most resources to invest in reproduction. Consistent with our predictions, the more specialized parasitoids were less plastic in some responses to host diet than the more generalist. However, patterns of egg load and size were variable across species. In general, there was a remarkable degree of reproductive effort-allocation constancy within parasitoid species. This may reflect more "time-limited" rather than "egg-limited" foraging strategies where the most expensive component of reproductive success is to locate and handle patchily-distributed and fruit-sequestered hosts. If so, egg costs, independent of degree of specialization, are relatively trivial and sufficient resources are available in fly larvae stemming from all of the substrates tested.

Fruit fly (Diptera: Tephritidae) research in Latin America: myths, realities and dreams

I offer a critical assessment of fruit fly research in Latin America based on the notion that many myths and misconceptions are forced upon students and young scientists or government officials. I argue that after an enlightening beginning of the century, during which many significant discoveries were made about the natural history of these insects, little progress has been observed in many areas of fruit fly research and management in Latin America during the past 50 years. This has been caused in part by the reductionist, single-species or pest-only approaches followed in the study of these marvelous insects, as well as by the scarcity of studies under natural conditions. To break this vicious cycle, I propose that we pay more attention to the natural history of non-pest and pest species, broaden the scope and widen the time scale of our studies, strengthen the theoretical and ecological underpinnings of fruit fly research in Latin America and foster the comparative approach whenever possible. I present several fruit fly myths (e.g., the status of certain fruits as fruit fly hosts and certain species as pests), review the status of knowledge in most areas of fruit fly research in Latin America, and discuss some possibilities for future studies. I conclude by proposing that on the threshold of the new millennium, the time seems appropriate to follow those early pioneers and once again push forward our understanding of fruit fly biology, ecology and behavior. To achieve this, we need to generate new paradigms and foster creative thinking among our students.

Parasitóides de moscas-das-frutas (Diptera: Tephritidae) associados a fruteiras tropicais

Foram encontradas espécies de himenópteros parasitando larvas de moscas-das-frutas no município de Conceição do Almeida, no Recôncavo Baiano, nas seguintes proporções: o Eucoilidae Aganaspis pelleranoi (Brèthes) (12,2%), os braconídeos Doryctobracon areolatus (Szépligeti) (81,4%), Utetes (Bracanastrepha) anastrephae (Viereck) (0,7%) e Opius spp. (0,7%) além da espécie introduzida Diachasmimorpha longicaudata (Ashmead) (5,0%). Foram feitas amostragens de setembro de 1995 a setembro de 1996, em frutos de goiaba (Psidium guajava L.), pitanga (Eugenia uniflora L.), carambola (Averrhoa carambola L.) e manga (Mangifera indica L.), caídos sob a copa das árvores. As pupas viáveis obtidas apresentaram parasitismo final de 7,4%, 43,9%, 10,2% e 19,0%, respectivamente. O parasitóide D. areolatus esteve presente em maior quantidade em todas as espécies de frutos, exceto em goiaba. D. longicaudata também foi detectado em todos os frutos coletados. Pitanga foi a fruteira de onde emergiu maior número de parasitóides (1.512 em 4.239 frutos coletados). A. pelleranoi foi o parasitóide predominante em goiaba.