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This study delves into the compatible use of a parasitoid with multifunctional endophytic Entomopathogenic Ascomycetes (EA) in IPM under greenhouse conditions. The parasitoid Hyposoter didymator was evaluated against Spodoptera littoralis in a multitrophic system with melon plants that were endophytically colonized by one of three EA strains (Metarhizium brunneum [one] or Beauveria bassiana [two]). In the first scenario, plants were inoculated by three different methods, and after infestation with noctuid larvae, the parasitoid was released at a 1:20 ratio. Microbiological and molecular techniques allowed the identification of progressive colonization throughout the whole plant life cycle, and for B. bassiana, approximately 20% of seeds from new fruits were colonized. The parasitoid was shown to be compatible with all strains and application methods, with total mortality rates ranging from 11.1 to 77.8%. Significant lethal and sublethal effects, a decrease in pupal weight and mortality of pupae showing abnormalities and an extension of the immature developmental times were observed for different strain–application method combinations. Additionally, the fungal treatments improved crop growth, as revealed by the significant gains in plant weight. In a second scenario (by inoculating plants with the fungi only by leaf spraying), and after infestation with noctuid larvae, the parasitoid was released at a 1:10 ratio, which revealed the remote fungal effect from the inoculation point and confirmed the compatibility of the parasitoid-EA-based strategy. These findings underscore the compatible use of a parasitoid with endophytic EA for S. littoralis control that can additionally exploit their multifunctionality for sustainable crop production. [ABSTRACT FROM AUTHOR]

Hyposoter didymator (Hymenoptera, Ichneumonidae) is a generalist solitary endoparasitoid of noctuid larvae. In the present work, we tested whether populations of H. didymator were divided in several genetically distinct taxa as described for many other generalist parasitoid species, and whether differences in H. didymator parasitism rates were explained by the insect host species and/or by the plant on which these hosts were feeding on. The genetic analysis of natural populations collected in different regions in France and Spain on seven different insect hosts and seven different host plants (775 individuals) showed that H. didymator populations belong to a unique single taxon. However, H. didymator seems to be somewhat specialized. Indeed, in the fields it more often parasitized Helicoverpa armigera compared to the other host species collected in the present work. Also, H. didymator parasitism rates in field conditions and semi-field experimental studies were dependent on the host plants on which H. armigera larvae are feeding. Still, H. didymator can occur occasionally on non-preferred noctuid species. One hypothesis explaining the ability of H. didymator to switch hosts in natura could be related to fluctuating densities of the preferred host over the year; this strategy would allow the parasitoid to avoid seasonal population collapses.

This study was carried out to improve the rearing methods of endoparasite Hyposoter didymator (Thunberg) for biological control release. The growth and the development of H. didymator on the first, second, and third instars of Spodoptera littoralis (Boisduval) and Helicoverpa armigera (Hübner) under laboratory conditions were investigated. Results indicated that S. littoralis was a suitable host for the rearing of H. didymator. The development time of the parasite on the second instar of both hosts was almost the same (~17 d). The age of the female parasite affected the percentage of adult emergence, pupal mortality, and females in the offspring reared on S. littoralis host. The best copulation period of H. didymator females and males was 36 h that resulted in 51.8% of females in the offspring. The male to female ratio during copulation period, as well as the presence of males after copulation, and the number of host larvae for each parasite female had no effect on parasitism. Results suggested that S. littoralis second instar is a suitable host for mass rearing of H. didymator parasite, which may improve the use of H. didymator as a biocontrol agent. [ABSTRACT FROM AUTHOR]

Abstract: An endoparasitic life style is widespread among Hymenoptera, and various different strategies allowing parasitoids to escape from the host encapsulation response have been reported. Species carrying polydnaviruses (PDVs), such as the ichneumonid Hyposoter didymator, generally rely on the viral symbionts to evade host immune responses. In this work, we show that H. didymator eggs can evade encapsulation by the host in the absence of calyx fluid (containing the viral particles), whereas protection of the larvae requires the presence of calyx fluid. This evasion by the eggs depends on proteins associated with the exochorion. This type of local passive strategy has been described for a few species carrying PDVs. Immune evasion by braconid eggs appears to be related to PDVs or proteins synthesized in the oviducts being associated with the egg. We report that in H. didymator, by contrast, proteins already present in the ovarian follicles are responsible for the eggs avoiding encapsulation. Mass spectrometry analysis of the egg surface proteins revealed the presence of host immune-related proteins, including one with similarities with apolipophorin-III, and also the presence of three viral proteins encoded by IVSPERs (Ichnovirus Structural Protein Encoding Regions). [Copyright &y& Elsevier]

Abstract: The venom gland is a conserved organ in Hymenoptera that shows adaptations associated with life-style diversification. Few studies have investigated venom components and function in the highly diverse parasitic wasps and all suggest that the venom regulates host physiology. We explored the venom of the endoparasitoid Hyposoter didymator (Campopleginae), a species with an associated polydnavirus produced in the ovarian tissue. We investigated the effects of the H. didymator venom on two physiological traits of the host Spodoptera frugiperda (Noctuidae): encapsulation response and growth rate. We found that H. didymator venom had no significant effect on host cellular immunity or development, suggesting that it does not contribute to parasitism success. The host physiology seemed to be modified essentially by the ovarian fluid containing the symbiotic polydnaviruses. Proteomic analyses indicated that the H. didymator venom gland produces a large variety of proteins, consistent with the classical hymenopteran venom protein signature, including: reprolysin-like, dipeptidyl peptidase IV, hyaluronidase, arginine kinase or allergen proteins. The venom extracts also contained novel proteins, encoded by venom genes conserved in Campopleginae ichneumonids, and proteins with similarities to active molecules identified in other parasitoid species, such as calreticulin, reprolysin, superoxide dismutase and serpin. However, some of these proteins appear to be produced only in small amounts or to not be secreted. Possibly, in Campopleginae carrying polydnaviruses, the host-modifying activities of venom became redundant following the acquisition of polydnaviruses by the lineage. [Copyright &y& Elsevier]

The ability to cope with plant defense chemicals differs between specialist and generalist species. In this study, we examined the effects of the concentration of the two main iridoid glycosides (IGs) in Plantago lanceolata, aucubin and catalpol, on the performance of a specialist and two generalist herbivores and their respective endoparasitoids. Development of the specialist herbivore Melitaea cinxia was unaffected by the total leaf IG concentration in its host plant. By contrast, the generalist herbivores Spodoptera exigua and Chrysodeixis chalcites showed delayed larval and pupal development on plant genotypes with high leaf IG concentrations, respectively. This result is in line with the idea that specialist herbivores are better adapted to allelochemicals in host plants on which they are specialized. Melitaea cinxia experienced less post-diapause larval and pupal mortality on its local Finnish P. lanceolata than on Dutch genotypes. This could not be explained by differences in IG profiles, suggesting that M. cinxia has adapted in response to attributes of its local host plants other than to IG chemistry. Development of the specialist parasitoid Cotesia melitaearum was unaffected by IG variation in the diet of its host M. cinxia, a response that was concordant with that of its host. By contrast, the development time responses of the generalist parasitoids Hyposoter didymator and Cotesia marginiventris differed from those of their generalist hosts, S. exigua and C. chalcites. While their hosts developed slowly on high-IG genotypes, development time of H. didymator was unaffected. Cotesia marginiventris actually developed faster on hosts fed high-IG genotypes, although they then had short adult longevity. The faster development of C. marginiventris on hosts that ate high-IG genotypes is in line with the 'immunocompromized host' hypothesis, emphasizing the potential negative effects of toxic allelochemicals on the host's immune response. [ABSTRACT FROM AUTHOR]

Abstract: The main effects and interactions between temperature and host instar on development and survival of Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae), as well as the effects of parasitism on the growth rate of the various host instars of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) were studied under laboratory conditions. The duration of development of immature stages of H. didymator in first, second, third, fourth and fifth instar of H. armigera larvae at five constant temperatures (15, 20, 25, 30, and 33°C) was recorded. Developmental time decreased significantly with increasing temperature within the range of 15–30°C. When parasitism took place on first and fifth host instars, the parasitoid development from egg stage up to adult emergence took significantly longer compared to other instars. Parasitoid survival did not vary linearly either with host stage or with temperature, and was generally lower in very young and older hosts in all temperatures tested: it decreased very quickly above 25°C, and fell to zero at 33°C. Between 15 and 25°C the survival of immature stages ranged from 54 to 76% when parasitized in the second and third host instars, respectively. Larval stages of H. didymator exhibited a flexible growth model (Regulator-conformer) that depended on host instar at parasitism. Parasitism by H. didymator reduced the weight gain of parasitized host larvae at an early stage of development (e.g. 1 day after parasitism) when the host larvae were parasitized in larger instars while this effect was delayed up to 4 days when smaller instars were parasitized. [Copyright &y& Elsevier]

Adults of the parasitoid Hyposoter didymator were topically treated with four insect growth regulator (IGR) insecticides at different doses, including their respective maximum field recommended concentrations (MFRCs) [registered in Spain or recommended by manufacturers]. Methoxyfenozide and tebufenozide (100, 500 and 1,000 mg/l) did not affect any life parameter or the first parasitoid's offspring. In contrast, diflubenzuron (100, 500 and 1,000 mg/l) and pyriproxyfen (75, 500 and 1,000 mg/l) caused sublethal effects, decreasing the offspring emergence as a result of the parasitoid mortality during its immature stages inside the host and the life span of female offspring. In a second part, pharmacokinetic studies using a 14C isotope of each IGR showed similar patterns of penetration through the cuticle, but different absorption and distribution rates inside the insect body. Cuticular penetration of pyriproxyfen reached about 99% in 3 days and those of diflubenzuron, methoxyfenozide and tebufenozide ranged from 82% to 86%. All insecticides were recovered from the reproductive system of insects and eggs. For pyriproxyfen and diflubenzuron absorption in the adult body tissues reach >65%, whereas this was only 40% for tebufenozide and methoxyfenozide. No statistical differences were found between sexes. The current data reflect that several mechanisms are likely to be involved in the selectivity of these products towards this parasitoid. [ABSTRACT FROM AUTHOR]

Abstract: An improved rearing method for the larval endoparasitoid Hyposoter didymator was developed in the laboratory considering the single locus complementary sex determination (sl-CSD) theory as well as other factors affecting sex ratio: (1) use of the preferred host of the parasitoid in nature; (2) appropriate host size (large enough to favor female development); (3) appropriate parasitoid age (experienced in parasitization); (4) implication of all genotypes on offspring production (unselected parasitizing couples); and (5) genetic variability (regular infusion of wild stock). Firstly, to corroborate the sl-CSD theory, a small rearing was sib-mated in seven generations until males accounted for more than 90%. Secondly, a new parasitoid rearing method was developed using a single large population and two inbred lines (as reservoirs of alleles) to maintain allelic diversity according to the Cook’s Model. The quality of insects obtained with this method was evaluated by measuring the percentages of parasitized hosts and adult emergence and the sex ratio of the progeny during 42 generations. Parasitized host percentages were >80% and an average of 40% of females were obtained in practically all generations. Low percentages (<2%) of dead immature stages were recorded, and life span of adults was 32±1.3 and 18±2.2d for females and males, respectively. The advantages of this rearing method compared to others previously developed for this parasitoid and its application to others hymenopteran parasitoid are discussed. [Copyright &y& Elsevier]

The loreyi leaf worm, Mythimna (Acantholeucania) loreyi Duponchel (Lepidoptera, Noctuidae), is a pest of gramineous crops and causes significant economic damage to maize. In field surveys on maize to determine the parasitoid community and its impact on the pest in the eastern Mediterranean region of Turkey, nine parasitoid species were found associated with immature stages of M. loreyi: The hymenopteran (Braconidae and Ichneumonidae) parasitoids Cotesia (=Apanteles) ruficrus (Haliday), Chelonus oculator Panzer, Meteorus ictericus Nees, Hyposoter didymator (Thunberg), Sinophorus sp.; and the dipteran (Tachinidae) parasitoids Pseudogonia rufifrons Wiedeman, Exorista rossica Mesnil, Gonia picea (Robineau-Desvoidy) and Linnaemya vulpina (Fallen) — the last three recorded for the first time as parasitoids of M. loreyi in Turkey. C. ruficrus was the dominant parasitoid species, being recovered from 38.5% of the larvae collected and was also the most prevalent species, existing in 91.0% of the fields in which M. loreyi was found. Total parasitism levels achieved by braconid species was 41.4%, by ichneumonid parasitoids 4.8%, and by tachinid parasitoids 1.9%. In a separate field experiment, seasonal population fluctuations and natural efficiency of C. ruficrus on M. loreyi were found to be 35.1% and 42.4%, respectively. Population levels of C. ruficrus were closely related to fluctuations in the population of M. loreyi, with parasitism ranging between 0 and 77.3% during the study. [ABSTRACT FROM AUTHOR]

Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) is an important larval parasitoid of several lepidopteran pests. Under laboratory conditions, the topical toxicity of selected insect growth regulator insecticides, azadirachtin (AZA), diflubenzuron (DFB), methoxyfenozide (MET), pyriproxyfen (PYR), and tebufenozide (TEB), and the naturalyte spinosad (SPIN) was tested against last (third)-instar larvae of this parasitoid up to the maximum field recommended concentration (MFRC). At MFRC, no abnormalities or mortality were scored for MET and TEB (IOBC toxicity classes 1). In contrast, AZA was slightly, PYR moderately, and DFB and SPIN harmful to the parasitoid (IOBC toxicity classes 2, 3, and 4, respectively). These ratings are the result of a reduction in rate of: (i) pupae formation, (ii) pupal mortality, (iii) adult longevity, (iv) parasitism, and (v) adult emergence. In addition, PYR and SPIN caused a direct mortality in the treated larvae. At sublethal concentrations, every insecticide but MET and TEB also affected these life history parameters of the parasitoid. The second part of the study focused on pharmacokinetic parameters important for the toxicological properties of these insecticides. We determined the recovery pattern of 14C-labeled DFB, MET, PYR, and TEB from parasitoid body, larval exuvia, and silken pupal cocoon after topical application to third-instar larvae. For MET, TEF, and PYR, >60% was recovered from the parasitoid body after 24 h, whereas this was only 12% for DFB, which was mostly detected in the silken cocoon (>60%). More than 25% PYR was also detected in the larval exuvia after three days. Data suggest that the silken pupal cocoon and the larval exuvia might play a role in eliminating insecticides. In conclusion, the current results indicated that MET and TEB are harmless to third larvae of H. didymator. In contrast, AZA, DFB, PYR, and SPIN are harmful and their use in IPM should be considered with caution until they are evaluated under field conditions. [Copyright &y& Elsevier]

The present study was conducted to determine egg and larval parasitoids of the beet armyworm Spodoptera exigua Hübner (Lepidoptera: Noctuidae), which is an important but sporadic pest in Turkey. High beet armyworm population levels were recently observed in fields of first and second crop maize in the southeast Mediterranean region of Turkey. The parasitoid species complex and its impact on the pest were analyzed in a 4-year study in first and second crop maize. The braconid larval parasitoids Microplitis rufiventris Kokujev, M. tuberculifer Wesmael, Meteorus ictericus Nees, Chelonus obscuratus (Herrich Schäffer) (an egg-larval parasitoid), Apanteles ruficrus (Haliday); the ichneumonid larval parasitoids Hyposoter didymator (Thunberg) and Sinophorus xanthostomus Gravenhorst; and the egg parasitoid Trichogramma evanescens (Westwood) were found to be the natural enemies attacking the pest. Among the parasitoid species the solitary endoparasitoid H. didymator was the most prevalent species, being reared from 40.5% of the parasitized larvae found. Higher parasitism rates were recorded on first crop than on second crop maize in every year. Possible reasons for this difference in larval parasitism between two growing seasons include lower population of the pest and reduced insecticide applications in first crop maize fields which permitted higher parasitism. However, parasitoid activity was insufficient to counterbalance the population growth of the pest on subsequent second crop maize. [ABSTRACT FROM AUTHOR]

The wasp Hyposoter didymator (Hymenoptera, Ichneumonidae) parasitizes several agricultural pest moths and could therefore be used in biological control. The 454 FLX Titanium pyrosequencing technology was used to define two distinct sets of multiplex combining 14 polymorphic microsatellite loci: 10 (referred to as HD) located within the genome of H. didymator and 4 (referred to as HdIV) located within the Ichnovirus genome which is integrated into the wasp genome. Genotyping of two populations collected in France on Helicoverpa armigera revealed that most of the loci are independent and at Hardy-Weinberg equilibrium. [ABSTRACT FROM AUTHOR]