Native Parasitoids Research Articles

No adverse effects of symbiotic control on the parasitism of Halyomorpha halys by egg parasitoids

The brown marmorated stink bug Halyomorpha halys is a polyphagous insect, which has a devastating impact on agricultural production in many countries. The alteration of symbiont vertical transmission, by removing symbionts from stink bug eggs (symbiotic control), has been recently introduced in control programmes against this insect. A major advantage of this strategy is the compatibility with natural enemies, since it allows an insecticide-free approach that is not harmful to other agroecosystem components. However, the effect of anti-symbiont products on parasitism by egg parasitoids is still unexplored. Here, we investigated the impact on parasitism by native (Anastatus bifasciatus, Ooencyrtus telenomicida and Trissolcus kozlovi) and exotic (Trissolcus japonicus and Trissolcus mitsukurii) parasitoids that attack H. halys eggs, after treatment with the micronutrient biocomplex Dentamet®, used for symbiotic control. The native wasp species were tested in no-choice bioassays, showing that treatment of the egg masses did not affect emergence percentages, but the non-reproductive effects were often reduced by the biocomplex. The exotic species T. japonicus and T. mitsukurii were used in no-choice and paired choice bioassays, showing an opposite influence of Dentamet® on emergence percentage and preference in the two species. No-choice tests indicated the highest successful parasitoid emergence on biocomplex-treated egg masses for T. japonicus, while no preference in the paired comparison with eggs treated with water or untreated. In contrast, T. mitsukurii displayed the lowest parasitism after Dentamet® treatment in no-choice tests, and preferred egg masses without Dentamet® in paired choice tests. We did not record any natural symbiont acquisition by the parasitoids emerged from H. halys egg masses, indicating that the wasp fitness is very unlikely to be altered by dysbiotic effects resulting from treatments. Therefore, our results support a further implementation of symbiotic control in different crops in combination with biological control, as sustainable options for H. halys integrated pest management.

Natural Parasitism Influences Biological Control Strategies Against Both Global Invasive Pests Ceratitis capitata (Diptera: Tephritidae) and Drosophila suzukii (Diptera: Drosophilidae), and the Neotropical-Native Pest Anastrepha fraterculus (Diptera: Tephritidae).

Ceratitis capitata (Wiedemann) and Drosophila suzukii (Matsumura) are two severe invasive pests widespread in all Argentinean fruit-producing regions. Both coexist with the Neotropical pest Anastrepha fraterculus (Wiedemann) in northern Argentina. The northwestern region shelters major soft fruit and Citrus producing and exporting industries, which are heavily affected by these dipterans. Eco-friendly strategies are under assessment in Argentina. This study mainly assessed D. suzukii, C. capitata, and A. fraterculus temporal abundance variations and their natural parasitism levels on a 1.5-ha-patch of feral peach trees within a disturbed secondary subtropical rainforest of northwestern Argentina. Fly puparia were mainly collected from the soil under fallen peach. Sampling was performed over three peach fruiting seasons. The most abundant pest species was C. capitata. Drosophila suzukii was only found in the last collecting period, but outnumbered A. fraterculus. Natural parasitism distinctly affected the temporal abundance of these dipterans: it significantly depressed C. capitata abundance in last sampling weeks, it did not substantially affect D. suzukii abundance, but it increased synchronously with the increase in the A. fraterculus abundance. Parasitism on C. capitata was mostly exerted by a combination of both a cosmopolitan pupal and a native larval parasitoid, while A. fraterculus was mainly parasitized by two indigenous larval parasitoids. Only three resident pupal parasitoids were associated with D. suzukii, of which the cosmopolitan Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) was the most significant. Data on the resident parasitoid impact are relevant for designing biocontrol strategies in noncrop habitats.

Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) in Minho (Northern Portugal): Bioecology, Native Parasitoid Communities and Biological Control with Torymus sinensis Kamijo (Hymenoptera: Torymidae)

The Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu, native to China, was first detected in Europe in Italy in 2002. In Portugal it was declared in 2014, and it has since affected the Portuguese chestnut production. The introduction of its natural parasitoid Torymus sinensis Kamijo started through inoculative releases according to the National Action Plan for the Control of Dryocosmus kuriphilus, established by the Direção Geral de Alimentação e Veterinária (DGAV), in 2015. This research was carried out during 2018 and 2019, in five chestnut orchards in the Minho region (Northern Portugal). Between January and March 2018, at each location, three monthly harvests of 100 buds were carried out to determine the infestation level. Between April and June 2018, 240 galls were harvested every two weeks, with the purpose of studying the bioecology of D. kuriphilus. In each sampling site, 160 galls were placed in emergence boxes to follow adults of the D. kuriphilus population, and 80 galls were dissected with a binocular magnifying glass, to count and record the evolution of the larval stages of D. kuriphilus and of the parasitoids. The identification of T. sinensis and native parasitoids was carried out. The parasitism rates and Simpson diversity indices were determined. The percentage of buds infested by D. kuriphilus was high in all studied places, varying between 67% and 80%, regardless of the number of T. sinensis releases made and of the chestnut cultivars present in each orchard. The highest rate of parasitism by T. sinensis was 0.5044% and it was recorded in an orchard where there were two releases of T. sinensis in 2016 and 2017 (Arcos de Valdevez—Rio Cabrão—P1). Considering that the exotic parasitoid has already been released in the region since 2016, its establishment in all the chestnut orchards studied was confirmed, although with very low parasitism rates. The natural parasitism associated with the native parasitoid species of D. kuriphilus was confirmed in this work, recording values between 34% and 51% of the parasitized chestnut galls, with 11 species of native parasitoids having been identified: Eupelmus azureos, Eupelmus uruzonus, Eurytoma brunnivientris, Eurytoma pistaciae, Megastigmus dorsalis, Mesopolobus sp., Ormyrus pomaceus, Sycophila biguttata, Sycophila iracemae, Sycophila variegatta and Torymus flavipes.

Native generalist natural enemies and an introduced specialist parasitoid together control an invasive forest insect.

Specialized natural enemies have long been used to implement the biological control of invasive insects. Although research tracking populations following biological control introductions has traditionally focused on the impact of the introduced agent, recent studies and reviews have reflected an appreciation of the complex interactions of the introduced specialist agents with native generalist natural enemies. These interactions can be neutral, antagonistic, or complementary. Here we studied the invasive defoliator winter moth (Operophtera brumata) in the Northeast USA to investigate the role of native, generalist pupal predators along with the introduced, host-specific parasitoid Cyzenis albicans. Prior research in Canada has shown that predation of winter moth pupae from native generalists increased after C. albicans was established as a biological control agent. To explain this phenomenon, the following hypotheses were suggested: (H1 ) parasitoids suppress the winter moth population to a density that can be maintained by generalist predators, (H2 ) unparasitized pupae are preferred by predators and therefore experience higher mortality rates, or (H3 ) C. albicans sustains higher predator populations throughout the year more effectively than winter moth alone. We tested these hypotheses by deploying winter moth pupae over 6 years spanning 2005 to 2017 and by modeling pupal predation rates as a function of winter moth density and C. albicans establishment. We also compared predation rates of unparasitized and parasitized pupae and considered additional mortality by a native pupal parasitoid. We found support for the first hypothesis; we detected both temporal and spatial density dependence, but only in the latter years of the study when winter moth densities were low. We found no evidence for the latter two hypotheses. Our findings suggest that pupal predators have a regulatory effect on winter moth populations only after populations have been reduced, presumably by the introduction of the host-specific parasitoid C. albicans.

The Oriental Chestnut Gall-wasp Dryocosmus Kuriphilus Yasumatsu, 1951, (Hymenoptera: Cynipidae) and Its Introduced and Native Parasitoids in Madeira Island, Portugal, with Notes on Some Other Parasitic Hymenoptera Reared from Gall Samples

The accidental introduction to Madeira of the invasive chestnut gall wasp (CGW), Dryocosmus kuriphilus, is reviewed, as is the subsequent biological control programme implemented by the Regional authorities. This control programme was based on the importation of a non-native parasitoid, Torymus sinensis. Results from five years of parasitoid release are presented, including a list of native parasitoid species associated with D. kuriphilus galls in Madeira. Five species of Hymenoptera are listed as new records for Madeira: Dryocosmus kuriphilus Yasumatsu, 1951; Torymus sinensis Kamijo, 1982; Bootanomyia dorsalis (Fabricius, 1798); Colpoclypeus florus (Walker, 1839), and Ufens foersteri (Kryger, 1918).

Evolution of parasitoid host preference and performance in response to an invasive host acting as evolutionary trap.

The invasion of a novel host species can create a mismatch in host choice and offspring survival (performance) when native parasitoids attempt to exploit the invasive host without being able to circumvent its resistance mechanisms. Invasive hosts can therefore act as evolutionary trap reducing parasitoids' fitness and this may eventually lead to their extinction. Yet, escape from the trap can occur when parasitoids evolve behavioral avoidance or a physiological strategy compatible with the trap host, resulting in either host‐range expansion or a complete host‐shift. We developed an individual based model to investigate which conditions promote parasitoids to evolve behavioral preference that matches their performance, including host‐trap avoidance, and which conditions lead to adaptations to the unsuitable hosts. The model was inspired by solitary endo‐parasitoids attacking larval host stages. One important aspect of these conditions was reduced host survival during incompatible interaction, where a failed parasitization attempt by a parasitoid resulted not only in death of her offspring but also in host killing. This non‐reproductive host mortality had a strong influence on the likelihood of establishment of novel host–parasitoid relationship, in some cases constraining adaptation to the trap host species. Moreover, our model revealed that host‐search efficiency and genetic variation in host‐preference play a key role in the likelihood that parasitoids will include the suboptimal host in their host range, or will evolve behavioral avoidance resulting in specialization and host‐range conservation, respectively. Hence, invasive species might change the evolutionary trajectory of native parasitoid species, which is important for predicting biocontrol ability of native parasitoids towards novel hosts.

Augmentative biological control of Halyomorpha halys using the native European parasitoid Anastatus bifasciatus: Efficacy and ecological impact

We report the first large-scale augmentative biological control project carried out in Europe against Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) using the native egg parasitoid Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae). During summer 2020, a total of 325,000 adults of A. bifasciatus were released at a rate of 1000 individuals/ha of orchard in 11 sites in Trentino-Alto Adige (Northern Italy). Parasitism parameters were compared between release and control (no release) sites, in which at least three egg masses naturally laid by H. halys were collected (for a total of 262 egg masses). Anastatus bifasciatus and Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae) were the dominant parasitoids, but parasitism by both species fluctuated widely among sites. At release sites, A. bifasciatus showed a significantly higher discovery efficiency (31.4%) and parasitism rate (16.7%) of H. halys egg masses than at control sites (1.7% and 1.2%, respectively). Parasitism by A. bifasciatus was not dependent on egg mass abundance at release sites, but at control sites a host density-dependent response was revealed by a positive relationship between parasitism and number of H. halys egg masses. On the other hand, parasitism by the adventive T. mitsukurii was not affected by either the releases of A. bifasciatus or by the abundance of H. halys egg masses per site. In conclusion, augmentative releases of A. bifasciatus contributed to increasing its parasitization of H. halys, without causing any negative effects on parasitization by naturally occurring species.

Identification, Microhabitat, and Ecological Niche Prediction of Two Promising Native Parasitoids of Tuta absoluta in Kenya.

Simple SummarySince the arrival of Tuta absoluta, a multivoltine insect species whose larvae develop in leaves, fruits, flowers, buds, and stems of tomatoes, producers are facing one of its biggest production challenges. The pest continues to invade new areas, causing heavy losses in the tomato value chain. Sprays of synthetic insecticides have shown very low efficacy on this pest because of its inclination to develop resistance to various insecticide-active ingredients. Biological control is one of the most promising solutions for the management of this pest. In this work, we investigated the most efficient indigenous parasitoids associated with T. absoluta in Kenya and their preferable habitat and ecological niche suitability. We identified two species, Stenomesius sp. near japonicus and Bracon nigricans, with up to 17% and 21% parasitism respectively. Stenomesius sp. near japonicus was more abundant in greenhouses and non-insecticide-treated tomatoes while B. nigricans was more abundant in the field tomatoes with a low abundance of Nesidiocoris tenuis. The ecological niche of these two species showed that B. nigricans was suitable for establishment in sub-Saharan Africa, a big part of South America, and Australia in both current and future scenarios.Associations between the South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), and its native parasitoids need to be updated to increase the implementation of pest control strategies. In this study, T. absoluta-infested tomato plants were collected from three regions in Kenya. The emerged parasitoids were identified, and their abundance was correlated with agroecological parameters, viz. cropping systems, and the abundance of the predator Nesidiocoris tenuis Reuter (Hemiptera: Miridae). The study further conducted a habitat suitability prediction for the identified parasitoids. Two parasitoid species, Bracon nigricans (Szépligeti) (Hymenoptera: Braconidae) and Stenomesius sp. near japonicus (Ashmead) (Hymenoptera: Eulophidae) emerged from T. absoluta immature stages, with parasitism rates ranging from 0 to 21% and 0 to 17% respectively. Insecticide application and open field cropping negatively influenced the parasitism by S. sp. nr japonicus. Low occurrence of N. tenuis positively affected B. nigricans parasitism. The predicted occurrence of parasitoid species indicated vast suitable areas for B. nigricans in sub-Saharan Africa, Australia, and South America. Low suitability was observed for S. sp. nr japonicus in Africa. Therefore, native parasitoids, especially B. nigricans could be considered for implementation as a biocontrol agent in the Integrated Pest Management program of T. absoluta.

Drosophila suzukiiManagement in Latin America: Current Status and Perspectives

AbstractSpotted-wing drosophila, Drosophila suzukii Matsumura, was first established in Latin America in Mexico in 2011. The vinegar fly has since been detected in 296 municipalities in Argentina, Brazil, Chile, Mexico, and Uruguay. Drosophila suzukii is polyphagous and is found on 64 host plants in 25 families in Latin America, with most hosts also exotic species. In Latin America, D. suzukii is attacked by 14 species of parasitoid wasps in the families Diapriidae, Figitidae, and Pteromalidae, which are promising native parasitoids for control of the pest. This article analyzes results from studies on monitoring, biological, chemical, and cultural control, and sterile insect techniques to provide a basis for the development of area-wide and sustainable D. suzukii management programs in Latin America. The review examines how D. suzukii has been managed in Latin America and how research conducted in this region can contribute to management of the species in other parts of the world.

Retrospective host-specificity testing shows Trissolcus basalis (Wollaston) and the native Trissolcus oenone (Dodd) (Hymenoptera: Scelionidae) have overlapping physiological host ranges in New Zealand

Retrospective host range testing is essential for understanding the physiological host range of introduced biological control agents (BCAs) and updating forecasts of non-target risks. It is especially important to conduct this work if there was no host range testing prior to release of the agent. Trissolcus basalis Wollaston was released in New Zealand in 1949 against green vegetable bug (Nezara viridula [L.]), but host range testing was never undertaken, and subsequent work in the 1960s was only of a qualitative nature and remains incomplete. The host-parasitoid complex between New Zealand pentatomids, T. basalis, and the native pentatomid parasitoid Trissolcus oenone Dodd, is therefore poorly understood. We conducted no-choice oviposition tests between the two resident Trissolcus species and all available New Zealand pentatomid species to characterise the physiological (=fundamental) host ranges of these parasitoids. We present the results of the first retrospective host-specificity study on T. basalis in New Zealand. Our results show T. basalis attacks and develops in all nine pentatomid taxa we exposed it to (including the endemic alpine species Hypsithocus hudsonae Bergroth), while T. oenone attacks and develops in seven out of eight pentatomid species we tested it against (and its capacity to attack H. hudsonae remains unknown). Parasitism efficiencies for all treatments exceeded 60%, while development times were similar for both parasitoids regardless of host. We discuss the importance of physiological host range testing for understanding potential non-target effects. Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) was recently approved for release in New Zealand against brown marmorated stink bug Halyomorpha halys Stål (Hemiptera: Pentatomidae), subject to its potential establishment, and we examine our results in the context of potential competition between introduced parasitoids for non-target species.

Anastrepha striata1 Parasitic Wasps in Guava Crops at Fragmented Landscapes of Nayarit, Mexico

Biological control using native parasitoids is a sustainable alternative to control tephritid flies. We tested whether landscape attributes surrounding guava trees might affect incidence of fruit flies and their parasitoids. From July to September 2019, we collected guava fruit at six locations at Nayarit, México. Pupae obtained from the fruit collected were reared in a laboratory until emergence of adult flies and parasitoids. We combined in situ georeferenced information with 2019 SPOT-7 satellite images to characterize the landscape in circular 500-m buffers. Spearman-rank tests were used to analyze correlation between abundance of Anastrepha striata and parasitoids with the proportion of each soil coverage. Mann-Whitney U and Kruskal-Wallis tests were used to evaluate the influence of management intensity with abundance of the fruit fly and parasitoids. We collected 15.7 kg of guava fruit from six localities. Anastrepha striata was at all localities sampled. Infestation of fruit was 9.4%, ranging from 0.5 to 35.2 larvae per kilogram. The four parasitic wasp species attacking A. striata were Doryctobracon areolatus, Trichopria drosophilae, Aceratoneuromyia indica, and Leptopilina boulardi and are new records of interactions in the State of Nayarit. The wasps attacked 7.5% of the fruit fly pupae.

Native egg parasitoids on Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) in Spain: Potential biological control agents?

AbstractLeptoglossus occidentalis Heidemann (Heteroptera: Coreidae), commonly known as western conifer seed bug (WCSB), is an invasive pest in the Mediterranean, where it has been associated with the decline of Pinus pinea L. kernel production. A biological control of WCSB populations with native egg parasitoids may reduce economic losses. With the purpose to obtaining egg masses laid in situ bags with WCSB, adults were placed, for three consecutive years, in a clone bank, and for 1 year, in a pine forest in Central Spain. To estimate the impact of the parasitoid species on the WCSB population, four parasitism indexes were calculated. The WCSB activity period was estimated for two consecutive years in the clone bank through visual monitoring. Two native parasitoid species were found on the WCSB eggs: Ooencyrtus pityocampae (Mercet) (Hymenoptera: Encyrtidae) and Ooencyrtus obscurus (Mercet) (Hymenoptera: Encyrtidae). The latter parasitoid species represents a new finding for WCSB eggs. In the clone bank, discovery efficiency of the egg masses, parasitism rate of the eggs, impact on host population and exploitation efficiency of the egg masses were significantly higher for O. obscurus than for O. pityocampae. In the pine forest, parasitism index values were also higher for O. obscurus, but significant differences were not found by species. Ooencyrtus obscurus reduced the WCSB population by 6.2%, down to 19.6%, while O. pityocampae reduced it by 1.0%, down to 11.5%. Predated eggs were recorded in both experimental sites in low amounts. Both native parasitoid species could be proposed as biological control agents (BCA) in a biological control programme (BCP) in Europe after measuring their effectiveness with laboratory assessments.

Experimental adaptation of native parasitoids to the invasive insect pest, Drosophila suzukii

The spread of invasive pests is increasing due to greater global transportation and climate change-mediated range shifts. In a new community, these invasive species provide a novel resource that native predators or parasitoids can evolve to utilise. For invasive agricultural pests, this could provide top-down control; however, initial attack rates on invasive species in the wild are generally low. The potential for rapid adaptive evolution of native species to improve developmental success on invasive species is unknown. We address this by focusing on Drosophila suzukii, a polyphagous invasive pest, and two cosmopolitan Drosophila parasitoids found in North America prior to the arrival of D. suzukii (Pachycrepoideus vindemiae and Trichopria drosophilae). We experimentally evolved three replicate populations of both species on D. suzukii and the cosmopolitan D. melanogaster, a common host for both parasitoids. We found evidence that P. vindemiae increased developmental success by 88% (95% credible intervals = [−14%, 254%]) and T. drosophilae increased developmental success by 259% [38%, 711%] on D. suzukii after only three generations of selection, despite very low founding sizes of 2 and 30 wasps, respectively. These results demonstrate that rapid evolution of increased virulence is possible even from low genetic diversity, with implications for integrating evolutionary techniques into biological control of invasive species.

Insect Rearing Techniques for Biological Control Programs, a Component of Sustainable Agriculture in Brazil.

Simple SummaryThis review describes the advances in BC for use in open fields in Brazil. These advances make our country a model for this type of pest control, especially since 1980, with the development of improved rearing techniques. In association with private companies, the use of BC has grown more than in the rest of the world, advancing by about 10–15% each year.This article describes the importance of rearing insects, whether on a small scale for research or a large scale for mass rearing, for use in biological control (BC) programs with macro-organisms. These inter- or multidisciplinary research programs are necessarily long-term and depend on rearing techniques for their complete development. Some successful examples of BC in Brazil are presented, including case studies of Trichogramma spp. These required broad bioecological studies that provided the basis for both mass rearing and transfer of the necessary technology to farmers. This has allowed Brazil to occupy a leadership position in biological control in “Open Fields”. For example, about three million ha are being treated with Trichogramma galloi (a native parasitoid), and about three and a half million ha with Cotesia flavipes (an exotic parasitoid) to control Diatraea saccharalis, the sugarcane borer. These natural enemies are produced by commercial firms, or by laboratories in sugar and alcohol plants themselves, in the case of C. flavipes.

Bottom-up effect of host protective symbionts on parasitoid diversity: Limited evidence from two field experiments.

Protective symbionts can provide effective and specific protection to their hosts. This protection can differ between different symbiont strains with each strain providing protection against certain components of the parasite and pathogen community their host faces. Protective symbionts are especially well known from aphids where, among other functions, they provide protection against different parasitoid wasps. However, most of the evidence for this protection comes from laboratory experiments.Our aim was to understand how consistent protection is across different symbiont strains under natural field conditions and whether symbiont diversity enhanced the species diversity of colonizing parasitoids, as could be expected from the specificity of their protection.We used experimental colonies of the black bean aphid Aphis fabae to investigate symbiont‐conferred protection under natural field conditions over two seasons. Colonies differed only in their symbiont composition, carrying either no symbionts, a single strain of the protective symbiont Hamiltonella defensa, or a mixture of three H. defensa strains. These aphid colonies were exposed to natural parasitoid communities in the field. Subsequently, we determined the parasitoids hatched from each aphid colony.The evidence for a protective effect of H. defensa was limited and inconsistent between years, and aphid colonies harbouring multiple symbiont strains did not support a more diverse parasitoid community. Instead, parasitoid diversity tended to be highest in the absence of H. defensa.Symbiont‐conferred protection, although a strong and repeatable effect under laboratory conditions may not always cause the predicted bottom‐up effects under natural conditions in the field.

Taxonomy of Whiteflies' Natural Enemies in Tamil Nadu Cotton Ecosystem

Native predators and parasitoids were identified against the invasive whiteflies in the cotton ecosystem. Over the past several decades, its control has been increasingly based on the use of its natural enemies. The natural enemies identified include Cheilomenes sexmaculata, Chrysoperla carnea, Diadiplosis sp, Orius insidiosus, two coleopteran beetles, Cybocephalus nipponicus, Delphastus catalinae and two species of Aphelinidae parasitoids, Encarsia guadeloupae and Encarsia dispersa. E. dispersa can be distinguished from E. guadeloupae by a combination of characters, including body colour, colour of the meso-scutellar suture, antennal segments, tarsal formula, etc. The identification of the predators and parasitoids was determined through taxonomical based on key characters. During the survey, several predators and parasitoids were recorded and maximum parasitism was recorded by Encarsia guadeloupae and Encarsia dispersa (Hymenoptera: Aphelinidae)

Natural Enemies and Pest Control in Field-Grown Crop in Southern Senegal

Crop pests are a permanent threat to horticultural production. Several control methods are recommended for their control, including biological control. This method based on the use of natural enemies is not well established. The objective of this study was to assess the diversity and abundance of natural enemies of crop pests. A survey of crops associated with pests was carried out on 144 fields in southern Senegal to measure the diversity and abundance of natural enemies of various crop pests, determine the native parasitoid complex and assess parasitism rates. Ecological indices were calculated to assess the diversity of natural enemies. A total of 25 natural enemy species were identified, including 15 parasitoids and 10 predators. Predatory Hemiptera and Parasitoid Hymenoptera were high biodiversity. The parasitism rates vary between 0 and 50% depending on the abundance of pests and parasitoid species. Knowledge of the diversity of natural enemies and the understanding of trophic interactions with pests are important in the development of biological crop protection in order to preserve resilience in agroecosystems.

Diversity of native and exotic parasitoids attacking agricultural pests in Ecuador: are Ecuadorian biocontrol programs in decline?

Diversity of native and exotic parasitoids attacking agricultural pests in Ecuador: are Ecuadorian biocontrol programs in decline?

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia

Impact of a nonnative parasitoid species on intraspecific interference and offspring sex ratio

In an assemblage of multiple predators sharing a single prey species, the combined effects of the component species may scale unpredictably because of emergent interspecific interactions. Prior studies suggest that chaotic but persistent community dynamics are induced by intra-/interspecific interactions between native and nonnative parasitoids competing over a shared host. Here, we test the impact of the nonnative parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) on the intraspecific interference and offspring sex ratio of the native parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae). We found that the nonnative parasitoid reduced intraspecific interference among native parasitoids and decreased the proportion of female offspring produced by the native parasitoid (predicted under conditions of reduced host availability). At higher host densities, the nonnative parasitoid contributed less to the total proportion of hosts parasitized, as its innate saturating Type II response changed to a dome-shaped Type IV response with increasing density of the native parasitoid, while the native parasitoid retained its increasing Type I response. This inverse host-density-dependent response between the two parasitoids and associated competitive superiority can explain the observed changes in parasitism; at high host densities, the searching efficiency of the native parasitoid increases via host feeding while the nonnative parasitoid experiences egg limitation. These results highlight the importance of the complementary top-down effects of multiple consumers on a single resource.