The multispecies stinkbug iflavirus Halyomorpha halys virus detected in the multispecies stinkbug egg parasitoid microwasp, Telenomus podisi (Ashmead) (Hymenoptera: Platygastridae)

Wasps are important parasitoids of stinkbugs and frequently exposed to various types of microorganisms through environmental contact and fecal-oral transmission route. Many parasitize stinkbug eggs and are commercially used in the field to control insect population. The parasitoid T. podisi is known for its high parasitism capacity and ability to target multiple species of stinkbugs. In this study we asked whether T. podisi exposed to eggs infected by a multispecies asymptomatic stinkbug virus, the Halyomorpha halys virus (HhV) would get infected. HhV is a geographically distributed multispecies iflavirus previously found to infect four stinkbug hosts, including three Brazilian species, Chinavia ubica, Euschistus heros and Diceraeus melacanthus, and T. posidi can parasitize all of them. As results, RT-PCR screening revealed positive samples for the HhV genome in two out of four tested pools of T. podisi, whereas the antigenome, indicative of replicative activity, was not detected. The wasps were raised in E. heros eggs that presented both the genome and the antigenome forms of the HhV genome. Subsequent RNA-deep sequencing of HhV positive T. podisi RNA pools yielded a complete genome of HhV with high coverage. Phylogenetic analysis positioned the isolate HhV-Tp (isolate Telenomus podisi) alongside with the stinkbug HhV. Analysis of transcriptomes from several hymenopteran species revealed HhV-Tp reads in four species. However, the transmission mechanism and the ecological significance of HhV remain elusive, warranting further studies to illuminate both the transmission process and its capacity for environmental propagation using T. podisi as a potential vector.

Biology, Thermal Requirements, and Fertility Life Table of Strains of Trichogramma foersteri (Hymenoptera: Trichogrammatidae) in Palpita forficifera (Lepidoptera: Crambidae)

Trichogramma foersteri Takahashi is a parasitoid recently identified in eggs of Palpita forficifera Munroe, considered the main pest of the olive tree in Brazil. The efficiency of a parasitoid is conditioned to several factors such as the temperature. The objective was to study the biology of the immature and adult phases at different constant temperatures (10, 15, 20, 25, and 30 °C), determine thermal requirements, and to elaborate a fertility life table for five strains (R1, R2, R3, R4, and R5) to T. foersteri. At 10 °C, there was no development of T. foersteri. The duration of the egg-adult period (days) was inversely related to temperature, ranging from 32 to 34 days (at 15 °C) to 6.5 to 7.5 days (at 30 °C). The thermal range evaluated did not influence parasitism (parasitism > 57%) and the sex ratio (sr > 0.74). The base temperature (Tt) was similar for all strains (approximately 12 °C), corresponding to a thermal constant (K) of 120.48 to 145.13 degree days. For the adult stage, T. foersteri had the highest rate of parasitism (> 48%) to 15 °C. The emergence rate ranged from 75 to 100%. The thermal range did not influence the sex ratio of the lines (sr > 0.70), but reduced the longevity from 50 days (at 15 °C) to 6 days (at 30 °C). Regarding the fertility life table, all strains of T. foersteri showed biological potential of development and growth in eggs of P. forficifera in the thermal range of 15 to 30 °C, important information for the establishment of biological control programs.

Selection of Strains of Trichogramma foersteri and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) for the Control of Palpita forficifera (Lepidoptera: Crambidae)

Palpita forficifera Munroe 1959 is a lepidopteran pest native to the Neotropical region and has been causing damage to olive tree crops in Brazil and Uruguay. The use of egg parasitoids of the genus Trichogramma may be a viable and sustainable alternative to pest management. The objective of the present work was to select species and/or strains of Trichogramma as possible agents of control for P. forficifera. Selections were made from five strains of Trichogramma foersteri Takahashi (R1, R2, R3, R4, and R5) collected in olive orchards of southern Brazil and four strains of Trichogramma pretiosum Riley (AC, PR, MJU, and RVI) from laboratory rearings. The strains of T. foersteri presented the longest periods from egg to adult (≈ 11.5 days) when compared to T. pretiosum (≈ 9.5 days). However, T. foersteri provided, in general, the highest daily percentage of parasitized P. forficifera eggs and, consequently, a higher rate of parasitism (between 50 and 69%) in relation to those of T. pretiosum (variation from 7 to 20%). In addition, T. foersteri provided a higher emergence rate (above 90%), with a sex ratio close to 1.0. However, all strains of T. pretiosum were longer-lived compared to adults of T. foersteri. From the biological parameters evaluated, two distinct groups were formed between T. foersteri and T. pretiosum. In general, T. foersteri has better potential for controlling P. forficifera, demonstrating its potential for use in field multiplication and release programs for the management of the olive larvae.

Insights from the biogeographic approach for biocontrol of invasive alien pests: Estimating the ecological niche overlap of three egg parasitoids against Spodoptera frugiperda in China

Spodoptera frugiperda, the fall armyworm, causes major damage to maize and >80 other crops worldwide. Since S. frugiperda successfully invaded China in 2018 via long-distance migration from Myanmar, it has caused major maize yield losses and posed a severe threat to maize production and food security. The biocontrol approach for S. frugiperda using natural enemies is environmentally safe and effective. Estimating the potential suitable area (PSA) for S. frugiperda and its natural enemies can provide insights for its biocontrol and management. Therefore, based on the global distribution records and bioclimatic variables, we modeled the PSA of S. frugiperda and three egg parasitoids in China using an ensemble model (EM). We found that the prediction results of the EM were more reliable than those of a single model. The PSAs of S. frugiperda and its three egg parasitoids were mainly attributed to temperature variables. The PSA of S. frugiperda was divided into migratory and overwintering areas using the mean January 10 °C isotherm from 2018 to 2022. In the overwintering area, Trichogramma chilonis had the largest PSA overlap with S. frugiperda (94.57 %), followed by Telenomus remus (68.64 %) and Trichogramma dendrolimi (67.53 %). Telenomus remus and Tr. chilonis were the most effective egg parasitoids against S. frugiperda in the overwintering area. In the migratory area, Tr. chilonis had the largest PSA overlap with S. frugiperda (91.36 %), followed by Tr. dendrolimi (81.70 %) and Te. remus (15.23 %). Trichogramma dendrolimi would be the most effective egg parasitoid against S. frugiperda in the Yangtze River Basin and northeastern China. Trichogramma chilonis was the most effective egg parasitoid against S. frugiperda in central China. Our findings indicate that the three native egg parasitoids would be "good regulators" of S. frugiperda outbreaks in China.

Olfactory response of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) to volatiles induced by transgenic maize

Plants not only respond to herbivorous damage but adjust their defense system after egg deposition by pest insects. Thereby, parasitoids use oviposition-induced plant volatiles to locate their hosts. We investigated the olfactory behavioral responses of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) to volatile blends emitted by maize (Zea mays L.) with singular and stacked events after oviposition by Spodoptera frugiperda Smith, 1797 (Hymenoptera: Trichogrammatidae) moths. Additionally, we examined possible variations in gene expression and on oviposition-induced volatiles. We used a Y-tube olfactometer to test for the wasp responses to volatiles released by maize plants oviposited by S. frugiperda and not-oviposited plants. Using the real-time PCR technique (qRT-PCR), we analyzed the expression of lipoxygenase and three terpene synthases genes, which are enzymes involved in the synthesis of volatile compounds that attract parasitoids of S. frugiperda. Olfactometer tests showed that T. pretiosum is strongly attracted by volatiles from transgenic maize emitted by S. frugiperda oviposition (VTPRO 3, more than 75% individuals were attracted). The relative expression of genes TPS10, LOX e STC was higher in transgenic hybrids than in the conventional (isogenic line) hybrids. The GC-MS analysis revealed that some volatile compounds are released exclusively by transgenic maize. This study provides evidence that transgenic hybrids enhanced chemical cues under oviposition-induction and helped to increase T. pretiosum efficiency in S. frugiperda control. This finding shows that among the evaluated hybrids, genetically modified hybrids can improve the biological control programs, since they potentialize the egg parasitoid foraging, integrating pest management.

An Integrative Taxonomy of a New Species of Trichogramma Westwood (Hymenoptera: Trichogrammatidae) with High Reproductive Capacity

A new species of Trichogramma Westwood (Hymenoptera: Trichogrammatidae) is described: Trichogramma foersteri sp. nov. Takahashi from eggs of Anticarsia gemmatalis Hübner, (Lepidoptera: Erebidae) a major soybean defoliating pest. The parasitoid was collected in São José dos Pinhais, Paraná State, Brazil, and molecular and morphological characters were used to confirm the identity of the new species. Preliminary biological data are provided to demonstrate its high capacity of parasitism. The new species is a potential candidate as a biological control agent against some lepidopteran-pests.

Pesticide selectivity to the parasitoid Trichogramma pretiosum: A pattern 10-year database and its implications for Integrated Pest Management

Trichogramma pretiosum is one of the main egg parasitoids used in the control of lepidopteran pests in Brazil. This natural enemy can be negatively affected by the use of insecticides, herbicides, and fungicides. The present work used a systematic review and meta-analysis to group information from multiple studies on the selectivity of pesticides (279 commercial products) in rice, corn, soybean, apple and peach crops for immature stages (egg-larva, pre-pupa, and pupa) and adult parasitoids. The selected studies used the International Organization for Biological and Integrated Control (IOBC) methodology with the same adaptations for T. pretiosum. The meta-analysis found that corn crops had the highest frequency of tests (2 0 7). The most frequently tested active ingredients (a.i.) were glyphosate, glyphosate isopropylamine salt, and sulfur at frequencies of 41, 32 and 24 tests, respectively. The pesticides registered for rice crops showed the greatest sublethal effects on T. pretiosum, with an approximately 47% reduction in parasitism (RP) or emergence (RE). The adult stage of the parasitoid showed greater sensitivity to the tested pesticides (65% RP), in comparison to the immature stages. In general, insecticides showed superior toxicity for all development stages of T. pretiosum, compared to herbicides and fungicides, regardless of the recommended dosage for the crop. The present study aggregates information related to selectivity for the four life stages of T. pretiosum, contributing significantly to the integration of biological control and chemical control in rice, corn, soybean, apple and peach crops in Brazil.

Notes on Macroteleia Westwood (Hymenoptera, Scelionidae) from China, with description of a new species

The wasp genus Macroteleia Westwood from China has been previously revised, but some species are only known from males. Here the females of two known species are described: M. carinigena Chen, Johnson, Masner & Xu and M. gracilis Chen, Johnson, Masner & Xu. In addition, one species is redescribed: M. variegata Kozlov & Kononova; and one species is described as new: Macroteleia xui Hong & Chen, sp. nov. Macroteleia ischtvani Kononova, syn. nov. is proposed as new synonym of M. variegata Kozlov & Kononova.

Sublethal effects of insecticides used in soybean on the parasitoid Trichogramma pretiosum

To control crop pests, parasitoid wasps of the genus Trichogramma are one alternative to the use of insecticides. Since a wide variety of agrochemicals may be applied to the same crops, it is essential to assess the selectivity of insecticides used for pest control on Trichogramma pretiosum. Information on which insecticides are less harmful to T. pretiosum can improve biological control using this insect, an important tactic in IPM programs for field crops. This study aimed to determine the effects of insecticides on the pupal stage and on the parasitism capacity of T. pretiosum. Lambda-cyhalothrin + thiamethoxam were slightly harmful and chlorpyriphos was moderately harmful to the pupal stage, while acephate, chlorfenapyr and flubendiamide, although considered innocuous, affected the succeeding generations of wasps, with low emergence of F1. Chlorfenapyr, chlorpyriphos and lambda-cyhalothrin + thiamethoxam reduced the parasitism, and acephate had a deleterious effect on the generation that contacted the insecticide residue. For an effective IPM program, it is important to apply selective insecticides. Further studies are needed to determine the selectivity of these insecticides under field conditions.

Seasonal parasitism and host specificity of Trissolcus japonicus in northern China

The brown marmorated stink bug, Halyomorpha halys (Stål), native to China, Japan, and Korea, has emerged as a harmful invasive pest of a variety of crops in North America and Europe. The Asian egg parasitoid Trissolcus japonicus has been identified as the most promising agent for classical biological control of invasive H. halys populations. A 4-year study evaluated the fundamental and ecological host ranges of T. japonicus as well as its phenology and impact on H. halys populations in fruit orchards in its native range in northern China. In laboratory no-choice tests, developmental suitability of eight non-target host species for T. japonicus was demonstrated by the successful production of progeny on the majority (>85%) of non-target host species tested. In field-collected, naturally laid egg masses, T. japonicus was the most abundant parasitoid associated with H. halys and Dolycoris baccarum, but was also sporadically found in Plautia crossota. Furthermore, it was regularly reared from sentinel egg masses of Menida violacea, Arma chinensis, and Carbula eoa. The only species that did not support development in the laboratory and field was Cappaea tibialis. Besides the benefit of having a high impact on H. halys populations in Northern China, the risk assessment conducted in the area of origin indicates that native Pentatomidae in North America and Europe could be negatively impacted by T. japonicus. Whether the benefits of T. japonicus outweigh the possible risks will have to be evaluated based on the outcome of additional host range studies in the two invaded regions.

New World species of the genus Calliscelio Ashmead (Hymenoptera, Platygastridae, Scelioninae)

The genus Calliscelio Ashmead is presumed to be a diverse group of parasitoids of the eggs of crickets (Orthoptera: Gryllidae). A least one species has been found to be an important factor in depressing cricket pest populations. The New World species of Calliscelio are revised. Forty-two species are recognized, 3 are redescribed: Calliscelio bisulcatus (Kieffer), Calliscelio laticinctus Ashmead, Calliscelio rubriclavus (Ashmead), comb. n.; and 38 are described as new: Calliscelio absconditum Chen & Johnson, sp. n., Calliscelio absum Chen & Johnson, sp. n., Calliscelio alcoa Chen & Masner, sp. n., Calliscelio amadoi Chen & Johnson, sp. n., Calliscelio armila Chen & Masner, sp. n., Calliscelio bidens Chen & Masner, sp. n., Calliscelio brachys Chen & Johnson, sp. n., Calliscelio brevinotaulus Chen & Johnson, sp. n., Calliscelio brevitas Chen & Johnson, sp. n., Calliscelio carinigena Chen & Johnson, sp. n., Calliscelio crater Chen & Johnson, sp. n., Calliscelio crena Chen & Johnson, sp. n., Calliscelio eboris Chen & Johnson, sp. n., Calliscelio extenuatus Chen & Johnson, sp. n., Calliscelio flavicauda Chen & Johnson, sp. n., Calliscelio foveolatus Chen & Johnson, sp. n., Calliscelio gatineau Chen & Johnson, sp. n., Calliscelio glaber Chen & Masner, sp. n., Calliscelio granulatus Chen & Masner, sp. n., Calliscelio latifrons Chen & Johnson, sp. n., Calliscelio levis Chen & Johnson, sp. n., Calliscelio longius Chen & Johnson, sp. n., Calliscelio magnificus Chen & Masner, sp. n., Calliscelio migma Chen & Johnson, sp. n., Calliscelio minutia Chen & Johnson, sp. n., Calliscelio paraglaber Chen & Johnson, sp. n., Calliscelio pararemigio Chen & Masner, sp. n., Calliscelio prolixus Chen & Johnson, sp. n., Calliscelio punctatifrons Chen & Johnson, sp. n., Calliscelio remigio Chen & Masner, sp. n., Calliscelio ruga Chen & Johnson, sp. n., Calliscelio rugicoxa Chen & Masner, sp. n., Calliscelio sfina Chen & Johnson, sp. n., Calliscelio storea Chen & Johnson, sp. n., Calliscelio suni Chen & Johnson, sp. n., Calliscelio telum Chen & Johnson, sp. n., Calliscelio torqueo Chen & Johnson, sp. n., Calliscelio virga Chen & Johnson, sp. n. Four species are treated as junior synonyms of Calliscelio rubriclavus (Ashmead): Anteris nigriceps Ashmead, syn. n., Caloteleia marlattii Ashmead, syn. n., Caloteleia grenadensis Ashmead, syn. n., and Macroteleia ruskini Girault, syn. n.

Insect parents improve the anti-parasitic and anti-bacterial defence of their offspring by priming the expression of immune-relevant genes

Insect parents that experienced an immune challenge are known to prepare (prime) the immune activity of their offspring for improved defence. This phenomenon has intensively been studied by analysing especially immunity-related proteins. However, it is unknown how transgenerational immune priming affects transcript levels of immune-relevant genes of the offspring upon an actual threat. Here, we investigated how an immune challenge of Manduca sexta parents affects the expression of immune-related genes in their eggs that are attacked by parasitoids. Furthermore, we addressed the question whether the transgenerational immune priming of expression of genes in the eggs is still traceable in adult offspring. Our study revealed that a parental immune challenge did not affect the expression of immune-related genes in unparasitised eggs. However, immune-related genes in parasitised eggs of immune-challenged parents were upregulated to a higher level than those in parasitised eggs of unchallenged parents. Hence, this transgenerational immune priming of the eggs was detected only "on demand", i.e. upon parasitoid attack. The priming effects were also traceable in adult female progeny of immune-challenged parents which showed higher transcript levels of several immune-related genes in their ovaries than non-primed progeny. Some of the primed genes showed enhanced expression even when the progeny was left unchallenged, whereas other genes were upregulated to a greater extent in primed female progeny than non-primed ones only when the progeny itself was immune-challenged. Thus, the detection of transgenerational immune priming strongly depends on the analysed genes and the presence or absence of an actual threat for the offspring. We suggest that M. sexta eggs laid by immune-challenged parents "afford" to upregulate the transcription of immunity-related genes only upon attack, because they have the chance to be endowed by parentally directly transferred protective proteins.

Impact of transgenerational immune priming on the defence of insect eggs against parasitism

Insects are known to prime the immune state of their offspring. However, although the beginning of insect life, the egg stage, is often greatly endangered by parasitism, no knowledge is available regarding whether transgenerational immune priming improves the immune responses of insect eggs to actual parasitoid attacks. Our study revealed suppression of the development of parasitoids in transgenerationally immune-primed Manduca sexta eggs and reduced emergence rates of parasitoids from these eggs. The higher defence efficiency of immune-primed M. sexta eggs against parasitoids was in agreement with the increased antibacterial activity and phenoloxidase activity of these eggs in response to parasitism compared to the eggs of control parents. Our study showed that immunochallenged insect parents could enable their offspring already in the egg stage to defend more efficiently against parasitic invaders. We discuss whether M. sexta benefits from transgenerational immune priming of eggs by limiting the population growth of egg parasitoids.

Ultrastructure of the female reproductive apparatus of the egg parasitoid Gryon pennsylvanicum (Ashmead) (Hymenoptera, Platygastridae)

The growing interest in Leptoglossus occidentalis, the conifer seed bug pest accidentally introduced into Europe in the 1990s, led us to investigate the female reproductive structures of the hymenopteran platygastrid Gryon pennsylvanicum, which is its candidate antagonist for biological control programmes. Our study revealed a genital apparatus with some characteristic features, such as an unusual length of the oviduct (divided into a long proximal and a short distal tract), the absence of accessory glands and the presence of a spermatheca provided with a small spermathecal gland. The ultrastructural investigation revealed that the shorter part of the common oviduct is involved in ion uptake whereas the longer part has two cell types with secretory function: the former with dense bodies and the latter with granular particles. The secretory contents of both are released into the oviduct lumen. The granular particles are formed in a complex of modified endoplasmic reticulum and appear as virus-like particles.