Oviposition behavior of the quasi-gregarious parasitoid, Ooencyrtus kuvanae (Hymenoptera: Encyrtidae)

The parasitoid wasp, Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae), is a natural enemy of the spongy moth, a significant forest pest in North America. We investigated the oviposition behavior of O. kuvanae females on spongy moth egg masses by (i) presenting female parasitoids with a single spongy moth egg mass that was replaced every day, 2nd day, 4th day, 8th day, or 16th day (which is the total length of the oviposition period) and (ii) presenting female parasitoids with 1, 2, 4, or 8 egg masses at a time. Offspring developmental length ranged from 18 to 24 days. On average, male offspring exhibited faster developmental times, emerging approximately 1 day ahead of females. The amount of time that adult females spent on an egg mass affected the number of parasitized eggs. Specifically, more offspring emerged in the 4-, 8-, and 16-day treatments than in scenarios involving daily or every second-day egg mass replacement. The percentage of male offspring decreased as the number of egg masses presented to females increased. Interestingly, the total number of female offspring remained constant, but the number of male offspring decreased with an increase in the number of egg masses and time spent by the parent within a patch. The observed sexual dimorphism in development time, the influence of resource availability on offspring sex ratios, and flexible oviposition patterns illustrate the adaptability of O. kuvanae in response to varying conditions. These insights have implications for our understanding of parasitoid-host interactions and their potential role in biological control strategies.

Age- and Density-Dependent Parasitism Rate and Development Time of the Generalist Egg-Parasitoid Ooencyrtus telenomicida (Hymenoptera: Encyrtidae) on Eggs of the Brown Marmorated Stink Bug, Halyomorpha halys

Halyomorpha halys (Hemiptera: Pentatomidae) is an invasive pest species that was imported into Greece in 2011 and since then, has caused severe qualitative and quantitative damage to economically important crops. Its management relies mainly on the use of broad-spectrum insecticides, with little to no information available concerning the potential use of native parasitoids in terms of classical biological control. Our study aimed to assess the parasitism rate and development time of the gregarious egg parasitoid Ooencyrtus telenomicida (Hymenoptera: Encyrtidae) on H. halys egg-masses, depending on several factors such as: (i) age of parasitoids, (ii) density of parasitoids, (iii) age of host eggs, and (iv) oviposition experience of parasitoids. According to our results, the younger the host eggs and the more parasitoids, the higher the parasitism rate achieved by adults of O. telenomicida, with the maximum mean value of the parasitism rate observed with 1-day-old host eggs and 4 parasitoid pairs (57.3%). On the contrary, the lowest mean value of the parasitism rate was observed with 4-day-old host eggs and 1 parasitoid pair (6.5%). Similarly, the age of parasitoids significantly affected parasitisation. The older the parasitoids were, the higher the parasitism rate achieved by adults of O. telenomicida, with a three-fold higher parasitism rate observed at 3-4 and 5-6-day-old O. telenomicida, compared to 1-2-day-old (31.8, 32.4, and 12.1%, respectively). Individuals that developed in younger host eggs displayed a shorter development time, and the shortest development time was observed for O. telenomicida laid by 2 parasitoid pairs. Parasitoid age did not affect the development time of O. telenomicida, although there was a tendency for individuals laid by younger female parasitoids to exhibit a shorter development time. Our findings provide valuable information on the potential use of O. telenomicida as a biocontrol agent of H. halys.

Evaluation of cold storage techniques to improve mass rearing of Cleruchoides noackae from Thaumastocoris peregrinus eggs

The egg parasitoid Cleruchoides noackae Lin & Huber, 2007 (Hymenoptera: Mymaridae) is originated from Australia and the main biological control agent of Thaumastocoris peregrinus Carpenter & Dellapé, 2006 (Hemiptera: Thaumastocoridae) on Eucalyptus L'Hér (Myrtaceae). Companies that grow Eucalyptus are in need of a mass rearing protocol to increase the number of individuals produced and improve the quality of this parasitoid. The aim of this study was to define a protocol for mass rearing C. noackae in T. peregrinus eggs, based in the evaluations of the key biological attributes of this parasitoid in the parental and F1 generations, after the cold storage of the parasitised host eggs. Two methods were tested as C. noackae rearing protocols. In the first, parasitised eggs of T. peregrinus by C. noackae were cold stored for 7 days after being left in a climatic chamber at 24 ± 2°C, 60 ± 10% RH and a photoperiod of 12:12 (light:dark) h (standard environmental conditions) for 3, 6, 9 or 12 days. In the second, T. peregrinus eggs parasitised by C. noackae were maintained in a climatic chamber under standard environmental conditions for 6 days, after which these eggs were cold-stored for 0 (control), 7, 14 or 21 days. Parasitism (%), and the development period (parasitism to adult) and female proportion (%) of C. noackae were evaluated. Based on the results (parental generation: parasitism, around 45%; F1 generation: parasitism, around 55%; development period, around 16 days; female proportion, around 60%), eggs should be stored at 5°C on the sixth day after parasitism by C. noackae and maintained at this temperature for 7 days. The cold storage of T. peregrinus eggs, after parasitism, can be included in the mass rearing protocols of the parasitoid C. noackae.

Telenomuscristatus Johnson (Hymenoptera, Scelionidae): new diagnostic data, distribution records and host associations

Specimens of an egg parasitoid wasp, Telenomuscristatus Johnson (Platygastroidea, Scelionidae), were reared from stink bug egg masses collected in the wild, in Maryland, United States. The egg masses were identified morphologically as Halyomorphahalys (Stål), Banasa Stål and Euschistus Dallas (Hemiptera, Pentatomidae). Molecular tools were used to further identify the Euschistus egg masses as E.servus (Say) and E.tristigmus (Say). All of these are new host associations for Te.cristatus. We also provide data to contribute to future identification of Te.cristatus: images of the holotype specimen and COI sequences from two disparate localities.

Feeding preference and intraguild interactions between the parasitoid Trichogramma achaeae and the predator Macrolophus pygmaeus, two biological agents of Tuta absoluta

BACKGROUND

Tuta absoluta is an exotic species and a major pest of tomato crops in Europe. Macrolophus pygmaeus and Trichogramma achaeae are two biocontrol agents widely used in integrated pest management programs of the South American tomato pinworm Tuta absoluta. In this study, we evaluated under laboratory conditions the (i) voracity of M. pygmaeus females fed on single diets of Tuta absoluta eggs parasitized or unparasitized by Trichogramma achaeae, (ii) voracity and feeding preference of M. pygmaeus females provided with mixed diets of Tuta absoluta eggs unparasitized and parasitized by Trichogramma achaeae and (iii) effect of competitive and intraguild interactions between M. pygmaeus and Trichogramma achaeae on the number of Tuta absoluta eggs consumed and/or parasitized. Lastly, we assessed under field conditions the effect of interspecific and intraspecific interactions between natural enemies on the number of Tuta absoluta eggs consumed and/or parasitized.

RESULTS

Macrolophus pygmaeus consumed more unparasitized than parasitized eggs of Tuta absoluta. Under mixed diet regimes, Manly indices revealed a feeding preference for unparasitized eggs, and a decrease in the total number of eggs consumed, as the proportion of available parasitized eggs increased, whereas the unparasitized eggs were consumed in direct proportion to their availability. Conspecific interactions between M. pygmaeus, in contrast to Trichogramma achaeae, revealed the possible occurrence of intraspecific competition. For intraguild heterospecific interactions, the number of Tuta absoluta eggs consumed by M. pygmaeus and parasitized by Trichogramma achaeae was lower than that predicted for additive and non-interactive scenarios. Under field conditions, a significant difference between the conspecific treatment and heterospecific treatments revealed a slightly higher success rate in controlling Tuta absoluta when both M. pygmaeus and Trichogramma achaeae were used simultaneously.

CONCLUSION

Macrolophus pygmaeus prefers unparasitized eggs of Tuta absoluta but inflicts intraguild predation on Trichogramma achaeae. In conspecific experiments, mutual interference between M. pygmaeus predators intensifies as the number of individuals increases, but for Trichogramma achaeae, it occurs in an unpredictable manner. Adding Trichogramma achaeae could significantly increase the level of control of Tuta absoluta compared to what could be achieved when only M. pygmaeus is present in glasshouse tomatoes. © 2023 Society of Chemical Industry.

Parasitism by Gryon aetherium (Hymenoptera: Scelionidae) on Bagrada hilaris (Hemiptera: Pentatomidae) eggs in northcentral California

Bagrada bug, Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae), is an invasive pest of cruciferous crops. The parasitoid Gryon aetherium Talamas (Hymenoptera: Scelionidae) is a promising biological control agent for B. hilaris because it can forage in the soil where B. hilaris deposits most of its eggs. In this study, we assessed parasitism by G. aetherium on B. hilaris eggs in situ in northcentral California, including the Salinas Valley where most cruciferous crops in the United States are grown. Parasitism was documented by leaving soil-filled trays under infested plants for 7-14 days, then removing eggs and holding them for emergence of parasitoids. Gryon aetherium accounted for over 99% of emerged parasitoids, and occurred at 11 of the 12 sampled sites. Of the 17,729 and 31,759 B. hilaris eggs collected in 2021 and 2022, 1,518 (8.84%) and 2,654 (8.36%) were parasitized by G. aetherium, respectively. Parasitism rates were generally higher inland and ranged from 3.64% to 44.93% in 2021 and from 1.01% to 23.04% in 2022, and never exceeded 15% on any sample dates at several coastal sites in the Salinas Valley. Discovery efficiency (a measure of the ability of parasitoids to locate egg patches) reached 80% or higher at all but 1 site, but exploitation efficiency (a measure of the ability of parasitoids to exploit the egg patch after it has been discovered) was generally <20%, suggesting that G. aetherium can locate egg patches efficiently but is less efficient at finding eggs within patches.

Biological basis for adoption of an isoline of Telenomus remus (Hymenoptera: Scelionidae) for an augmentative biological-control program for Spodoptera frugiperda (Lepidoptera: Noctuidae)

The widely distributed, polyphagous fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797), is one of the most important crop pests worldwide. The egg-parasitoid wasp, Telenomus remus Nixon, 1937, is frequently described as a possible control agent for S. frugiperda. We selected an isoline of T. remus and evaluated its parasitism potential (for 24 h) in S. frugiperda eggs, in laboratory conditions, and also its ability to fly at different temperatures and relative humidity levels, aiming to provide basic information about this isoline. The selected isoline maintained good flight capacity without affecting its parasitism efficiency or developing inefficient haplotypes for biological-control programs, compared across generations to a regularline laboratory-reared for more than 60 generations. The flight capacity of the isoline was best at 25-30 °C and relative humidity 70-90%.

Biology and quality assessment of Telenomus remus (Hymenoptera: Scelionidae) and Trichogramma spp. (Hymenoptera: Trichogrammatidae) in eggs of Spodoptera spp. for augmentative biological control programs

The Spodoptera complex of the family Noctuidae, represented here by S. frugiperda (J.E. Smith), S. eridania (Stoll), S. albula (Walker), and S. cosmioides (Walker), is an important group of crop pests in Brazil. Spodoptera frugiperda and S. eridania are invasive in Africa, and the former also in Asia and Oceania. The egg parasitoids Telenomus remus Nixon (Hymenoptera: Scelionidae) and Trichogramma spp. (Hymenoptera: Trichogrammatidae) are potential control agents for field use against these noctuids. We evaluated the parasitism efficiency, development, and flight capacity of an isofemale line and a regular line of T. remus, and 2 genetically variable populations of Trichogramma pretiosum Riley and Trichogramma atopovirilia Oatman and Platner (Hymenoptera: Trichogrammatidae) in these 4 members of the Spodoptera complex. All parasitoids were able to develop in the 4 hosts. The parasitoids showed good flight capacity, except for the regular line of T. remus. The Trichogramma species, despite having high viability and female:male sex ratios, showed poorer parasitism performances than T. remus. The regular T. remus line also showed good parasitism capacity and high viability but had a predominance of males. In general, the isofemale line of T. remus showed good rates of parasitism and flight capacity as well as a high viability and sex ratio, proving to be a potential candidate for an augmentative biological-control program for Spodoptera spp Guenée (Lepidoptera: Noctuidae).

Posterior concentration of Wolbachia during the early embryogenesis of the host dynamically shapes the tissue tropism of Wolbachia in host Trichogramma wasps

Introduction

The bacterial endosymbiont, Wolbachia spp. induce thelytokous parthenogenesis in certain parasitoid wasps, such as the egg parasitoid wasps Trichogramma spp. To complete the cycle of vertical transmission, Wolbachia displays efficient transovarial transmission by targeting the reproductive tissues and often exhibits strong tissue-specific tropism in their host.

Method

The present study aimed to describe the basic Wolbachia distribution patterns that occur during the development of Wolbachia-infected, thelytokous Trichogramma dendrolimi, and T. pretiosum. We used fluorescence in situ hybridization (FISH) to investigate Wolbachia signal dynamics during early embryogenesis (from 30 to 120 min). Wolbachia titers and distributions from the embryo to adult stages of Trichogramma after early embryogenesis were detected by absolute quantitative polymerase chain reaction (AQ-PCR) and FISH. The symmetry ratios (SR) of the Wolbachia signals were calculated using the SR odds ratios in the anterior and posterior parts of the host. The SR was determined to describe Wolbachia tropism during early embryogenesis and various developmental stages of Trichogramma.

Results

Wolbachia was concentrated in the posterior part of the embryo during early embryogenesis and the various developmental stages of both T. dendrolimi and T. pretiosum. Wolbachia density increased with the number of nuclei and the initial mitotic division frequency during early embryogenesis. The total Wolbachia titer increased with postembryogenesis development in both T. dendrolimi and T. pretiosum. However, the Wolbachia densities relative to body size were significantly lower at the adult and pupal stages than they were at the embryonic stage.

Discussion

The present work revealed that posterior Wolbachia concentration during early host embryogenesis determined Wolbachia localization in adult wasps. By this mechanism, Wolbachia exhibits efficient vertical transmission across generations by depositing only female Wolbachia-infected offspring. The results of this study describe the dynamics of Wolbachia during the development of their Trichogramma host. The findings of this investigation helped clarify Wolbachia tropism in Trichogramma wasps.

Emergence Response of Telenomus podisi (Hymenoptera: Scelionidae) to Field Temperature Originated from Colonies Reared at Different Temperature Regimes

We studied the impact of field temperature on the emergence of Telenomus podisi Ashmead (Hymenoptera: Scelionidae) after being released as either protected (encapsulated) or unprotected pupae close to adult emergence. Two independent bioassays (protected pupae vs. unprotected pupae) were carried out in a randomized block experimental design in a 2 (parasitoid rearing temperature regimes) ×4 (release positions within plant canopy) factorial scheme. One of the T. podisi colonies was reared at a constant temperature (25 °C) and 12:12 h L:D (Light: Dark) photoperiod. The second T. podisi colony was reared at fluctuating temperatures (20 °C during 12 h D and 30 °C during 12 h of L). Each bioassay had five replicates. Each replicate contained 40 pupae from each rearing temperature and release position within plant canopy. Parasitoid pupae were released in the bottom third, middle third, or upper third of the plant's canopy, as well as between planting lines. Each bioassay was repeated six times (in different plant developmental stages: R₁, R₂, R_3, R₄, R₅ and R₆). There was no difference in emergence of parasitoids between colonies reared at different temperatures after exposure to field conditions. Emergence of T. podisi was reduced after pupae exposure to temperatures above 35 °C in the field, regardless of the rearing temperature. Telenomus podisi tolerates temperature fluctuations for emergence as long as they fit the optimal range (20 to 30 °C).

Is Integrated Management of Gymnandrosoma aurantianum Possible with Trichogramma atopovirilia and Novel Products Used in Citrus Orchards in Brazil?

In Brazil, the citrus fruit borer, Gymnandrosoma aurantianum Lima, 1927, is a serious pest in orange orchards, causing an annual loss of 80 million US dollars, and is managed with multiple insecticide applications, often 56 in a single season. On the other hand, the parasitoid wasp Trichogramma atopovirilia Oatman & Platner, 1983 has the potential for controlling G. aurantianum by attacking its eggs. Considering the intensive insecticide applications in citrus orchards in Brazil to control the large complex of pests, especially Diaphorina citri Kuwayama, 1908, evaluation of the harmful effects of insecticides on T. atopovirilia is important to maximize efficiency in managing G. aurantianum. Here, we tested the effects of new products used in citrus orchards (cyantraniliprole, cyantraniliprole + abamectin, abamectin, sulfoxaflor, spinetoram, flupyradifure, and Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora) on adults and pupae of T. atopovirilia. Of the insecticides tested, spinetoram caused the highest impacts on T. atopovirilia parasitism, longevity, emergence, and mortality. The other products caused more sublethal than lethal effects and were classified as 1 and/or 2 in the IOBC/WPRS classification. Abamectin, cyantraniliprole, cyantraniliprole + abamectin, and the entomopathogenic fungus C. fumosorosea were classified as short-lived. Except for spinetoram, these products were classified as selective. In this study, spinetoram was considered harmful to T. atopovirilia and, therefore, should be managed carefully in IPM programs combining this parasitoid. In order to safely use this insecticide, one should respect the interval of release of the parasitoid, which is 21 days after its spraying. The novel products tested, cyantraniliprole, cyantraniliprole + abamectin, abamectin, sulfoxaflor, and the entomopathogenic fungi C. fumosorosea were selective and non-persistent to T. atopovirilia. These products are possible replacements for non-selective insecticides to achieve higher control from both chemical and biological tools.

Two new host records for Centrodoraitalica Ferrière (Hymenoptera, Aphelinidae) from eggs of Tettigoniidae (Orthoptera, Ensifera) in northeastern Italy

The egg parasitoid Centrodoraitalica Ferrière is reported for the first time from sentinel eggs of two species of Tettigoniidae (Orthoptera), Pachytrachisgracilis (Brunner von Wattenwyl) and Eupholidopteraschmidti (Fieber). In Italy, only two hosts of this parasitic wasp are known, one of which is a tettigoniid species. Exposure of sentinel eggs represented a useful method to detect new host associations of this parasitoid species that can search for their host's eggs in the ground. The parasitoids were identified by comparing our specimens with those of the type series, and the original description of C.italica.

Wolbachia-infected Trichogramma dendrolimi is outcompeted by its uninfected counterpart in superparasitism but does not have developmental delay

BACKGROUND

Wolbachia infection increases the superparasitism frequency of Trichogramma females and provides an opportunity for horizontal intraspecific transmission. However, superparasitism may lead to interstrain competition between Wolbachia-infected Trichogramma offspring and their uninfected counterparts. This study investigated the outcome of interstrain intrinsic competition between Wolbachia-infected thelytokous strain (W) and uninfected bisexual strain (B) of Trichogramma dendrolimi. To determine the developmental rate of both strains, the sizes of immature stages of T. dendrolimi offspring at different times after parasitisation were measured in single parasitism and superparasitism conditions.

RESULTS

The results reflect increased superparasitism by Wolbachia-infected females compared with uninfected females. Trichogramma females did not discriminate between host eggs previously parasitised by either B or W females. When the first oviposition was performed by B females, the B offspring outcompeted W offspring deposited later. Although when W offspring was deposited 8 h earlier than the B offspring, it gained no advantage over B offspring. Regardless of parasitism conditions, differences in the development rate between W and B offspring were not significant.

CONCLUSION

The results reconfirmed that W females presented a higher tendency for superparasitism than B females, and showed that B offspring outcompeted W offspring even when the latter was deposited 8 h earlier. The inferiority of Wolbachia-infected Trichogramma compared with their uninfected counterparts is not due to the developmental delay. This study provides insights into the effects of intrinsic competition on the control efficacy of Wolbachia-infected Trichogramma against pests in biological control programs. © 2022 Society of Chemical Industry.

Identification of Chelonus sp. from Zambia and Its Performance on Different Aged Eggs of Spodoptera frugiperda

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a migratory pest endemic, to tropical and subtropical regions of America. Biological control can effectively and sustainably control pests over a long period of time while reducing the frequency of pesticide use and ensuring the safety of agricultural produce. In our study, the egg-larval Chelonus species (Chelonus bifoveolatus) from parasitized eggs of Spodoptera frugiperda in Zambia were described and identified based on morphological and genetic characteristics. To evaluate the efficiency of C. bifoveolatus, their parasitism suitability on 0- to 2-day FAW eggs under laboratory conditions was compared. The results showed that C. bifoveolatus could accept all FAW eggs at 0-, 1- and 2-day-old age and complete development successfully. Significant differences were found among 0-, 1-, and 2-day-old host eggs with respect to egg-larva developmental duration of C. bifoveolatus, and the egg-larva developmental duration on 2-day-old eggs was significantly lower than those on 0- and 1-day-old eggs. No significant differences were observed in the parasitism, pupation, emergence, and female rates for C. bifoveolatus on various age eggs of FAW. Generally, the parasitism rate, pupal rate, and emergence rate at various ages of FAW eggs were higher than 90%, 75%, and 82%, respectively, and the longevity of female parasitoids was longer than male parasitoids, and the sex ratio of females to males was nearly 1:1. Our results indicate that C. bifoveolatus performed well on various ages of FAW eggs and is a potential biological control agent against FAW in Africa.

Survey of Trichogramma (Hymenoptera: Trichogrammatidae) Natural Populations in Quebec Cranberry Bogs and Identification Using rDNA ITS-2 Sequence Analysis

The province of Quebec, Canada is the most important organic cranberry growing region worldwide. However, insect pest management methods are limited, and growers face significant yield loss each year, mostly caused by lepidopteran pests. Egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) are effective biocontrol agents of lepidopteran pests in many forests and agricultural systems. Herein, a two-year, large-scale population survey of Trichogramma spp. was performed using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) as sentinel eggs in Quebec organic cranberry bogs. Collected specimens were identified by sequencing ribosomal DNA of the Internal Transcribed Spacer 2 (ITS-2) region and subjected to resemblance analysis with reference specimens for identification. Our results confirm that at least four Trichogramma species naturally occur in the studied agroecosystem. Those species are T. brassicae Bezdenko, T. minutum Riley, T. ostriniae (Pang et Chen), and T. pretiosum Riley. While some species have already been reported in cranberry bogs, this represents the first mention of T. brassicae and T. ostriniae as well as the first mention of T. minutum in Quebec cranberry bogs. All species collected are native from Eastern Canada except T. ostriniae. These species can be considered as biocontrol agent candidates for cranberry lepidopteran pests, but further efficacy trials are needed to identify the best species for each pest.

Reproductive attributes and functional response of Anastatus japonicus on eggs of Antheraea pernyi, a factitious host

BACKGROUND

Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is a solitary egg endoparasitoid that has been studied for inundative biological control of Halyomorpha halys Stål (Hemiptera: Pentatomidae) in China. In this study, we assessed the reproductive attributes and functional response of Anastatus japonicus on a factitious host, Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Anthelidae) at 25 ± 1 °C, 70 ± 5% relative humidity and 16 h:8 h light/dark photoperiod.

RESULTS

The mean lifetime fecundity of Anastatus japonicus females was 404.3 progeny produced over an average oviposition period of 42.3 days. The sex ratio of adult progeny was slightly male biased (51.2%), whereas more female progeny were produced before day 20 of a female's life. Single 1-day-old mated Anastatus japonicus females exhibited a type II functional response to increasing host densities (1-50 eggs), with an inverse host density-dependent pattern of percent parasitism. The upper limit to the daily attack rate was estimated as 7.6 Antheraea pernyi eggs. Furthermore, mutual interference among Anastatus japonicus females occurred when increasing densities of parasitoids (1, 2, 4, 8, 16) were exposed to 30 host eggs.

CONCLUSION

Laboratory functional response result revealed that individual Anastatus japonicus might be unable to respond effectively to increasing host density in the field, which could be compensated by releasing larger numbers of wasps. Strong mutual interference among foraging Anastatus japonicus females should be considered in any future inundative biological control programs for the sustainable management of Halyomorpha halys or other host insect pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of different Philosamia ricini (Lepidoptera: Saturniidae) cold storage periods on Ooencyrtus pityocampae and Ooencyrtus kuvanae (Hymenoptera: Encyrtidae) rearing

Ooencyrtus pityocampae and Ooencyrtus kuvanae are egg parasitoids that are considered potential candidates for the control of different pest species through inundative release. The aim of this study was to assess the effects of different cold-storage periods of Philosamia ricini eggs (host) on the rearing parameters of O. pityocampae and O. kuvanae. Host eggs were stored at 3 °C, and a factorial experiment involving two parasitoid species, nine host storage periods (1, 5, 10, 15, 30, 45, 60, 75 and 90 days) and a control, and two host ages (1 and 2 days) was conducted, with 10 replications including 40-P. ricini eggs each. Adult emergence, development time, longevity, and fecundity were investigated. The parasitoid adult emergence percentage significantly varied with storage duration. These values were lower in O. kuvanae than in O. pityocampae. The development time of O. kuvanae progeny increased in both host age groups except in the 1-day storage period subgroup. However, the development times of the progeny of O. pityocampae reared on one-day-old eggs stored for 5, 10, 60, and 75 days were increased, and the development times of the progeny of O. pityocampae reared on 2-day-old eggs stored for 45 and 90 days were increased. The longevity of the F1 progeny of O. kuvanae was negatively affected by storage time. There was no difference in the longevity of the F1 progeny of O. pityocampae compared to that of the control. Additionally, the fecundities of the F1 progeny of O. pityocampae and O. kuvanae were 54.7 and 47.0 offspring/female, respectively. These results provide useful information for guiding the development of mass rearing methodologies for both parasitoid species.

Penetrance during Wolbachia-mediated parthenogenesis of Trichogramma wasps is reduced by continuous oviposition, associated with exhaustion of Wolbachia titers in ovary and offspring eggs

BACKGROUND

Thelytokous Wolbachia-infected Trichogramma wasps are superior to bisexual uninfected wasps regarding biological control programs. However, continuous oviposition weakens the parthenogenesis-inducing (PI) strength of Wolbachia. Whether this reduced PI strength relates to decreases in the titer of Wolbachia in the ovary and offspring eggs of Trichogramma remains unclear. Here, using fluorescence in situ hybridization (FISH) and reverse transcription quantitative polymerase chain reaction (RT-qPCR) methods, we investigated how the penetrance of Wolbachia-mediated parthenogenesis, Wolbachia density, and distributions of two Wolbachia-infected Trichogramma species, T. pretiosum (TP) and T. dendrolimi (TD), were influenced by different host access treatments [newly-emerged virgin females (NE), 7-day-old females without access to host eggs (NAH), and 7-day-old virgin females with access to host eggs (AH)].

RESULTS

Continuous oviposition decreased Wolbachia PI strength and titers in TP and TD. Continuous oviposition in AH decreased Wolbachia titers in abdomen and offspring eggs of TP and TD females, compared with NAH and NE; NAH had a lower thorax Wolbachia titer than NE. The numbers of parasitized host eggs and offspring wasps, and emergence rates of offspring deposited by AH were lower than those of NE and NAH, for either species.

CONCLUSION

Weakened PI strength, driven by continuous oviposition in Trichogramma wasps, is associated with Wolbachia titer exhaustion in ovary and offspring eggs. Wolbachia density is dependent on PI strength in Trichogramma wasps, highlighting the side effects of continuous oviposition regarding thelytokous Wolbachia-infected Trichogramma in biological control programs. © 2022 Society of Chemical Industry.

Revision of the World Species of Megaphragma Timberlake (Hymenoptera: Trichogrammatidae)

Megaphragma species are important models for basic organismal research, and many are potential biological control agents. We present the first extensive revision of species of the genus Megaphragma based on morphological and molecular data. Our revision includes all previously described species, 6 of which are synonymized, and 22 of which are described here as new. We also provide the first key to all species of the genus and reconstruct their phylogeny based on 28S and CO1 molecular markers. The following species are synonymized with M. longiciliatum Subba Rao: M. aligarhensis Yousuf and Shafee syn. nov.; M. amalphitanum Viggiani syn. nov.; M. decochaetum Lin syn. nov.; M. magniclava Yousuf and Shafee syn. nov.; M. shimalianum Hayat syn. nov.M. anomalifuniculi Yuan and Lou syn. nov. is synonymized with M. polychaetum Lin. The following species are described as new: M. antecessor Polaszek and Fusu sp. nov.; M. breviclavum Polaszek and Fusu sp. nov.; M. chienleei Polaszek and Fusu sp. nov.; M. cockerilli Polaszek and Fusu sp. nov.; M. digitatum Polaszek and Fusu sp. nov.; M. fanenitrakely Polaszek and Fusu sp. nov.; M. funiculatum Fusu, Polaszek, and Viggiani sp. nov.; M. giraulti Viggiani, Fusu, and Polaszek sp. nov.; M. hansoni Polaszek, Fusu, and Viggiani sp. nov.; M. kinuthiae Polaszek, Fusu, and Viggiani sp. nov.; M. liui Polaszek and Fusu sp. nov.; M. momookherjeeae Polaszek and Fusu sp. nov.; M. nowickii Polaszek, Fusu, and Viggiani sp. nov.; M. noyesi Polaszek and Fusu sp. nov.; M. pintoi Viggiani sp. nov.; M. polilovi Polaszek, Fusu, and Viggiani sp. nov.; M. rivelloi Viggiani sp. nov.; M. tamoi Polaszek, Fusu, and Viggiani sp. nov.; M. tridens Fusu, and Polaszek sp. nov.; M. uniclavum Polaszek and Fusu sp. nov.; M. vanlentereni Polaszek and Fusu sp. nov.; M. viggianii Fusu, Polaszek, and Polilov sp. nov.

Effect of Different Constant Temperatures on Life History and Life Table Parameters of Trichogramma euproctidis (Hymenoptera: Trichogrammatidae)

Temperature has a profound effect on performance and behavior of egg parasitoids. Egg parasitoids are a well-known alternative for the control of lepidopterous pests. Selected life history parameters of Trichogramma euproctidis (Girault) (Hymenoptera: Trichogrammatidae), an established egg parasitoid species in Khuzestan- Southwest Iran, were appraised at eight constant temperatures (22.5, 25, 27.5, 30, 32.5, 35, 37.5, and 40°C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as the host. We found significant effects of temperature on the number of parasitized eggs, development time, sex ratio, progeny's longevity, and fecundity. T. euproctidis developed on E. kuehniella eggs at all temperatures tested, but performed best at 32.5°C. At this temperature, they parasitized the most eggs, produced the most female progeny, and had high rates of survival. Our findings revealed that temperature significantly affected the longevity of female progeny and fecundity of T. euproctidis. A life table analysis confirmed that temperature resulted in optimal effects on T. euproctidis life history. Net reproductive rate (R0) of T. euproctidis was different among the temperatures tested. The intrinsic rate of increase (r) was positively correlated with temperature from 22.5 to 32.5°C and then decreased from 35 to 40°C. Generation time (T) and doubling time (DT) decreased as temperature increased from 22.5 to 37.5°C and then increased at 40°C. These data suggest that this strain of T. euproctidis is adapted to high temperatures and harsh environmental conditions and has the potential to be used in integrated management programs in Southwest Iran.

Diversity and Parasitism by Parasitic Wasps That Attack Dalbulus maidis (Hemiptera: Cicadellidae) on Year-Round and Seasonal Maize Agroecosystems

Agroecosystems undergo frequent anthropogenic disturbance that may affect the diversity, community, and abundance of natural enemies living there. In the tropics, annual crops such as maize are planted two times (year-round crops) or one time (seasonal crops) per year. Little is known about how natural enemies of insect pests respond to maize agroecosystems planted one vs. two times during each annual cycle. The objective was to investigate the diversity and parasitism of egg parasitoids of the pest Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) in maize agroecosystems planted year-round and seasonally. Potted maize plants with D. maidis eggs were placed within these two maize agroecosystems to attract egg parasitoids during the maize-growing wet season in Mexico. In these two maize agroecosystems, similar levels of diversity were found, using the Shannon-Wiener index (H'). Communities of parasitic wasps were found attacking the eggs of D. maidis in both maize agroecosystems, but there were differences in the composition of these communities. In the year-round maize agroecosystem, Paracentrobia sp. near subflava (Girault) (Hymenoptera: Trichogrammatidae) was the most common, while Anagrus virlai Triapitsyn (Hymenoptera: Mymaridae) was most common in the seasonal maize. A greater total abundance and total rate of parasitoid emergence were found in the year-round maize agroecosystem compared with the seasonal maize. In addition, a positive relationship between the number of D. maidis eggs and parasitoid abundance was found in both maize agroecosystems. However, a negative density dependence between the number of D. maidis eggs and the percentage of parasitism was found in both maize agroecosystems.

Thermal Requirements of Ooencyrtus submetallicus (Hym.: Encyrtidae) and Telenomus podisi (Hym.: Platygastridae) Parasitizing Euschistus heros Eggs (Hem.: Pentatomidae)

Simple Summary

The brown stink bug, Euschistus heros, is the most abundant species infesting Brazilian soybean crops, causing significant yield losses. This stink bug is controlled with chemical insecticides, although the use of biological control with the egg parasitoids Ooencyrtus submetallicus and Telenomus podisi is increasing. Our objective in this study was to evaluate the development of O. submetallicus and T. podisi in E. heros eggs at different temperatures, and to estimate the number of annual generations for seven representative soybean-producing regions in Brazil. In the comparative biology study, the sex ratio and individuals per egg were higher for O. submetallicus in all regions. In the study of thermal requirements, the temperatures of 16, 19, 22, 25, 28, 31, and 33 °C were tested. The base temperature (Tb) for O. submetallicus and T. podisi was found to be 9.3 and 6.7 °C, and the thermal constant (K) was 336.9 and 272.7 degree-days, respectively. The average number of annual generations was estimated from the average temperatures of the last ten years in each region; based on these results, both parasitoids presented a higher number of generations than the host in all regions. O. submetallicus and T. podisi have the same ability to parasitize and develop in the eggs of E. heros under the conditions studied; in addition, both exhibited development and satisfactory parasitism at temperatures between 19 and 31 °C. The development of the two parasitoids was faster than E. heros, and the number of generations was higher for the seven studied localities.

Abstract

Temperature is one of the abiotic factors that strongly influences the biology and behavior of insects. In this study, we assessed the development of egg parasitoids Ooencyrtus submetallicus and Telenomus podisi parasitizing Euschistus heros eggs at different temperatures, and estimated the average number of generations for seven representative soybean-producing regions in Brazil. A comparative biology study was conducted, where the percentage of parasitism and emergence, life cycle duration (egg–adult), and longevity were found to be similar between O. submetallicus and T. podisi. The sex ratio and the number of individuals emerged from parasitized egg were higher in O. submetallicus in all regions. In the study of thermal requirements, temperatures of 16, 19, 22, 25, 28, 31, and 33 °C were tested. O. submetallicus and T. podisi developed at temperatures between 16 and 31 °C. The base temperature (Tb) for O. submetallicus and T. podisi was 9.3 and 6.7 °C, respectively; the thermal constant (K) was 336.9 and 272.7 degree-days, respectively. The estimated average number of annual generations of both parasitoids was higher than the host. O. submetallicus and T. podisi have the same ability to parasitize and develop in eggs of E. heros under the conditions studied. Both parasitoids exhibited satisfactory development and parasitism at temperatures between 19 and 31 °C. The development of both parasitoids was faster than their host, and the number of generations was higher for the seven studied localities.

Performance of Two Trichogrammatid Species from Zambia on Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Simple Summary

Two egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) from parasitized eggs of fall armyworm (FAW) Spodoptera frugiperda in Zambia were identified by using a combination of both molecular and morphological characters. We compared the parasitism capabilities of the two species with three native Chinese trichogrammatid species (T. ostriniae, T. leucaniae and T. japonicum) using 0- to 2-day-old FAW eggs. Both parasitoid species accepted eggs of all ages tested and completed their development successfully. Trichogrammatoidea lutea females showed the highest parasitism rate of host eggs among the five tested species. T. mwanzai had the shortest developmental time on all test age eggs. Of the five parasitoid species reared on FAW eggs, T. lutea performed the best overall, while T. japonicum was the worst performing of the parasitoids.

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a noctuid moth native to the tropical and subtropical Americas that has successfully invaded Africa and Asia, where it is has become a serious threat to food security as a pest of cereals and other crops. Biological control is an environmentally friendly means of combating the pest and contributes to an integrated pest management approach. In our study, two egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) found in parasitized fall armyworm eggs in Zambia were identified by using a combination of both molecular and morphological characteristics. To evaluate their potential and efficiency on 0- to 2-day-old fall armyworm eggs, we compared their parasitism capabilities with three Trichogramma species native to China (T. ostriniae, T. leucaniae and T. japonicum) under laboratory conditions. The results showed that both parasitoid species would accept 0-, 1- and 2-day-old fall armyworm eggs, and complete their development successfully. Trichogramma mwanzai and T. lutea preferred parasitizing 0- and 1-day-old eggs over 2-day-old eggs. Trichogrammatoidea lutea females supplied with fall armyworm eggs produced the highest parasitism rate of host eggs among the five tested species, while T. mwanzai had the shortest developmental time on all test age eggs. In general, T. lutea was the best performing of the five species when reared on fall armyworm eggs, while T. japonicum was the worst. There were no significant differences, however, in percent emergence in the five test species when reared on fall armyworm eggs.

Assessing the Potential of Inoculative Field Releases of Telenomus remus to Control Spodoptera frugiperda in Ghana

In response to the threat caused by the fall armyworm to African maize farmers, we conducted a series of field release studies with the egg parasitoid Telenomus remus in Ghana. Three releases of ≈15,000 individuals each were conducted in maize plots of 0.5 ha each in the major and minor rainy seasons of 2020, and compared to no-release control plots as well as to farmer-managed plots with chemical pest control. No egg mass parasitism was observed directly before the first field release. Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season, while 72-100% of egg masses were parasitized in the minor rainy season, during which pest densities were much lower. However, no significant difference in egg mass parasitism was found among the T. remus release plots, the no-release control plots and the farmer-managed plots. Similarly, no significant decrease in larval numbers or plant damage was found in the T. remus release fields compared to the no-release plots, while lower leaf and tassel damage was observed in farmer-managed plots. Larval parasitism due to other parasitoids reached 18-42% in the major rainy season but was significantly lower in the minor rainy season, with no significant differences among treatments. We did not observe significant differences in cob damage or yield among the three treatments. However, the lack of any significant differences between the release and no-release plots, which may be attributed to parasitoid dispersal during the five weeks of observation, would require further studies to confirm. Interestingly, a single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus and, thus, merits further investigation in the context of developing IPM strategies against FAW.

Preempting the Arrival of the Brown Marmorated Stink Bug, Halyomorpha halys: Biological Control Options for Australia

The brown marmorated stink bug Halyomorphahalys (Stål) (Hemiptera: Pentatomidae) is native to Northeast Asia, but has become a serious invasive species in North America and Europe, causing major damage to crops. While it has not established itself in Australia, it has been intercepted at the border several times, indicating that future incursions and establishment are a case of when, not if. Biological control is one of the few control options for this species and will be important for managing H.halys should it become established in Australia. Prioritizing species that could be used as biological control agents would ensure Australia is prepared. This study summarizes the literature on natural enemies of H. halys in its native and invaded ranges and prioritizes potential biological control agents of H.halys that could be used in Australia. Two egg parasitoid species were identified: Trissolcusjaponicus (Ashmead) and Trissolcusmitsukurii (Ashmead) (Hymenoptera: Scelionidae). Future efforts to develop biological control should focus on T. mitsukurii, as it is already present in Australia. However, little is known about this species and further work is required to: (1) assess its potential effectiveness in parasitizing H. halys, (2) determine its current distribution and (3) host range in Australia.

Optimal Conditions for Diapause Survival of Aprostocetus fukutai, an Egg Parasitoid for Biological Control of Anoplophora chinensis

Simple Summary

Diapause is a critical state of an insect’s life cycle when it undergoes arrestment of growth and/or reproduction to survive adverse environmental conditions and/or food shortage. Aprostocetus fukutai is a specialist egg parasitoid of the citrus longhorned beetle, Anoplophora chinensis, a high-risk invasive woodboring pest. The parasitoid overwinters as diapausing mature larva in the host egg and emerges in early summer in synchrony with the egg-laying of A. chinensis. Here, we determined the optimal conditions for diapause survival of this parasitoid. We showed that the parasitoid had a low (36.7%) diapause survival rate inside host eggs laid on potted plants due to desiccation or tree wound defense response under semi-natural conditions. Under laboratory rearing conditions, when parasitized host eggs were extracted from wood, the parasitoid did not survive at low humidity (44% RH). Survival rate increased with humidity, reaching the highest at 100% RH. Survival rate also increased with increasing chilling period temperature from 2 to 12.5 °C. Post-diapause developmental time decreased with increased humidity or temperature, but the reproductive fitness of the parasitoid was not significantly affected by the temperature regimes. Overall, high humidity (100% RH) and mild temperatures (12.5 °C) are the most suitable survival conditions for the diapausing parasitoid and thus should be used in laboratory rearing.

Abstract

Aprostocetus fukutai is a specialist egg parasitoid of the citrus longhorned beetle Anoplophora chinensis, a high-risk invasive pest of hardwood trees. The parasitoid overwinters as diapausing mature larvae within the host egg and emerges in early summer in synchrony with the egg-laying peak of A. chinensis. This study investigated the parasitoid’s diapause survival in parasitized host eggs that either remained in potted trees under semi-natural conditions in southern France or were removed from the wood and held at four different humidities (44, 75, 85–93 and 100% RH) at 11 °C or four different temperature regimes (2, 5, 10 and 12.5 °C) at 100% RH in the laboratory. The temperature regimes reflect overwintering temperatures across the parasitoid’s geographical distribution in its native range. Results show that the parasitoid resumed its development to the adult stage at normal rearing conditions (22 °C, 100% RH, 14L:10D) after 6- or 7-months cold chilling at both the semi-natural and laboratory conditions. It had a low survival rate (36.7%) on potted plants due to desiccation or tree wound defense response. No parasitoids survived at 44% RH, but survival rate increased with humidity, reaching the highest (93.7%) at 100% RH. Survival rate also increased from 21.0% at 2 °C to 82.8% at 12.5 °C. Post-diapause developmental time decreased with increased humidity or temperature. There was no difference in the lifetime fecundity of emerged females from 2 and 12.5 °C. These results suggest that 100% RH and 12.5 °C are the most suitable diapause conditions for laboratory rearing of this parasitoid.

Susceptibility of different developmental stages of Trichogramma parasitoids to insecticides commonly used in the Mediterranean olive agroecosystem

Insecticide application and augmentative parasitoid releases are often considered incompatible. However, pesticide applications and parasitoid releases can be integrated into a pest management scheme if there is careful time scheduling of these interventions. In this study, we assessed the influence of commonly used insecticides (chlorpyrifos-methyl, deltamethrin, pyriproxyfen, thiamethoxam) in olive agroecosystems to two currently present Trichogramma parasitoids in the Mediterranean basin. Exposure to insecticides in relation to parasitoid's development was also tested. Both, insecticide type and application time influenced parasitism and the emergence rates of the two parasitoid species. Chlorpyrifos-methyl had the strongest impact on parasitoids resulting in low numbers of emerged adults followed by deltamethrin. The two parasitoids also exhibited different levels of susceptibility to the insecticides used. Potential integration of insecticides to integrated pest management using Trichogramma parasitoids is discussed.

Biology and Population Dynamics of the American Vine Moth and the Potential Biocontrol with Trichogramma pretiosum

The American grapevine moth (AGVM), Lasiothyris luminosa (Razowski & Becker) (Lepidoptera: Tortricidae), was recently registered as a new pest for table grapes in the Northeast region of Brazil. In the present study, two approaches were made aiming to aid information to support management strategies for the new pest control: (i) study AGVM biology in the laboratory and its population dynamics in the field and (ii) evaluate Trichogramma pretiosum Riley as a potential biological control method against L. luminosa. The AGVM population dynamics showed a similar trend in the three grapevine monitored vineyards. The larvae started occurring at 30 days after pruning (DAP), pre-bloom stage, with a peak population between 54 and 78 DAP, following a decrease until harvest. The AGVM females larva, pupa, and egg-adult period were longer than males. The egg-adult period was 42.1 and 45.2 days for male and females, respectively. Trichogramma pretiosum was able to parasitize L. luminosa eggs. The T. pretiosum egg-adult period was 10.2 days with a 98.5% pupa survivorship at 25 °C. The release of T. pretiosum in the vineyards resulted in 65.5 to 73.2% AGVM egg parasitism. Our findings bring the first biological and population dynamics information for L. luminosa, which can help developing efficient approaches to monitor and control the pest in grapevines. The release of T. pretiosum in the vineyard is a potential biological control option to AGVM.

Temperature Impact on Telenomus podisi Emergence in Field Releases of Unprotected and Encapsulated Parasitoid Pupae

This work aimed to evaluate the influence of temperature on the emergence of Telenomus podisi throughout the soybean development cycle, using encapsulated and unprotected pupae releases, in four different possible locations where pupae can be deposited during release. The trial was carried out in a randomized block design in a 2 × 4 factorial scheme: two parasitoid pupae release strategies (encapsulated and unprotected) × four pupae locations (between soybean lines of planting, bottom third, middle third, or upper third of plant canopy) with 5 replicates. There were no significant interactions between the studied factors. In the vegetative stage (V2 and V9), a smaller percentage of emergence of parasitoid adults was observed between soybean lines of planting (37.1% and 23.4% for V2 and V9 , respectively). The highest maximum temperatures were recorded between the soybean lines, with the greatest variations in maximum and minimum temperatures (55.2°C and 21.3°C) in V2 and (52.8°C and 23.9°C) in V9. In the reproductive stages (R1, R4, and R7), the observed temperatures were lower when compared to those observed in the vegetative stages (V2 and V9), with no difference in the emergence of parasitoid adults, which was above 70% in stage R1 and above 80% in R4 and R7. Regarding the pupae (encapsulated or unprotected), both allowed similar adult emergence. Therefore, it can be concluded that both unprotected and encapsulated pupae can be released, but those releases during the soybean vegetative development stage should be avoided due to the high temperatures to which pupae can be exposed.

Taxonomic study of Baeosega and its allies, with description of a new species of Nipponosega (Hymenoptera, Chrysididae, Amiseginae)

Three related genera of Asian Amiseginae, Baeosega Krombein, Nipponosega Kurzenko & Lelej, and Okinawasega Terayama are revised. The male of N.yamanei Kurzenko & Lelej and the female of O.eguchii Terayama are newly described. The following new synonymies are proposed: Baeosegahumida Krombein, 1984 = B.laticeps Krombein, 1984, syn. nov.; Nipponosegayamanei Kurzenko & Lelej, 1994 = N.kantoensis Nagase, 1995, syn. nov. A new species of Nipponosega, N.lineatasp. nov. is described based on a female from Thailand. A key to genera and species of Baeosega, Nipponosega and Okinawasega is given.

Trissolcus kozlovi in North Italy: Host Specificity and Augmentative Releases against Halyomorpha halys in Hazelnut Orchards

Simple Summary

The Asian brown marmorated stink bug, Halyomorpha halys, is an invasive crop pest introduced into Europe in the 2000s. Due to its high harmfulness, and the increased chemical use for its control in the invaded areas, research has focused on biological control. In North Italy, the native parasitoid Trissolcus kozlovi emerged from field-collected H. halys eggs and proved to successfully parasitize H. halys eggs in the laboratory. Therefore, since little is known on T. kozlovi, this study aimed at assessing its physiological host range on 12 bug species in the laboratory, as well as its potential as a biological control agent of H. halys in the field by releases in two hazelnut orchards. In the laboratory, among the tested bug species, only Nezara viridula was an unsuitable host. On all others, T. kozlovi was able to develop, even if at different levels, suggesting that it is as oligophagous as Trissolcus japonicus, with which it shares many similarities. In the field, T. kozlovi was found to parasitize H. halys eggs, but only immediately after field releases. Therefore, further field surveys are required to assess its favorably environmental conditions and its possible interaction with T. japonicus, currently present in Italy.

Abstract

Trissolcus kozlovi (Hymenoptera: Scelionidae) emerged from field-laid eggs of Halyomorpha halys (Hemiptera: Pentatomidae) in North Italy, and it emerged in significantly higher numbers from fresh H. halys eggs compared to other native scelionids. Since few data on T. kozlovi are available, its host-specificity and some biological traits were investigated in laboratory tests, and its impact after augmentative releases was evaluated in two hazelnut orchards. Among the 12 tested bug species (Hemiptera: Pentatomidae, Scutelleridae), only Nezara viridula was an unsuitable host, while the highest offspring proportions were obtained from Arma custos, Pentatoma rufipes, and Peribalus strictus, followed by Acrosternum heegeri and Palomena prasina. Furthermore, when reared on P. strictus, T. kozlovi showed a high longevity as well as a high adaptation to H. halys eggs. In both hazelnut orchards, T. kozlovi emerged from H. halys eggs after field releases, but it was not found in the next two years. The physiological host range of T. kozlovi was quite similar to that of T. japonicus, and probably T. kozlovi has just begun to attack H. halys as a new host. This aspect needs to be further investigated, as well as its favorable environmental conditions, its distribution and also its possible interaction with T. japonicus, currently present in Italy.

Add Germany to the List-Adventive Population of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) Emerges in Germany

Simple Summary

The brown marmorated stink bug, Halyomorpha halys, is an invasive pest species of global economic importance. It has a very broad host range and causes severe damages in agricultural, horticultural, and fruit crops. Control measures, including available chemical and mechanical options, have often proved insufficient. Surveys of natural enemies in the newly invaded areas have also shown that natural biological control is generally too low to control H. halys populations in the long run. In its native Asian range, egg parasitoids in the genus Trissolcus play an important role in controlling H. halys. Since the mid-2010s, adventive populations of Trissolcus japonicus, a dominant egg parasitoid of H. halys in Asia with a narrow host range, have been reported from several countries with prior establishment of H. halys. Here, we report the first discovery of T. japonicus in Germany. This finding corroborates a northbound expansion of the range of T. japonicus in Europe, along with H. halys.

Abstract

The brown marmorated stink bug, Halyomorpha halys, is a polyphagous pest species of worldwide economic importance. Since the mid-1990s, it has invaded and become established in various countries outside its native Asian range. In the newly invaded areas, biological control by native natural enemies has been shown to be insufficient in the long-term control of this severe pest. Adventive populations of Trissolcus japonicus, an important biological control agent of H. halys in Asia, have been reported from North America and some European countries since the mid-2010s. This egg parasitoid species seems to follow in the wake of the establishment of H. halys populations outside their native Asian range. Here, we report the first discovery of an adventive population of T. japonicus in Germany. In 2020, adult T. japonicus were recovered from parasitized H. halys egg masses (naturally laid and sentinel egg masses) and collected in ruderal areas using an insect suction sampler. The arrival of T. japonicus in Germany, unintentional through pathways yet unknown, corroborates a northbound expansion of its range within Europe. Further field surveys will show the extent of its dispersal and establishment capacities within this new distribution area.

Host Patch Use and Potential Competitive Interactions Between Two Egg Parasitoids From the Family Scelionidae, Candidate Biological Control Agents of Bagrada hilaris (Hemiptera: Pentatomidae)

Two egg parasitoids from Pakistan, Gryon sp. nr. gonikopalense Sharma (Hymenoptera: Scelionidae) and Trissolcus hyalinipennis Rajmohana & Narendran (Hymenoptera: Scelionidae), are currently being investigated as potential classical biocontrol agents for Bagrada hilaris Burmeister. The former is the most promising because of its ability to attack B. hilaris eggs in soil, but the latter was recently discovered in California. This study detailed the patch use and oviposition behavior of both species and assessed their relative foraging efficiency. We also investigated possible competitive interactions by assessing 1) the occurrence of intra- and interspecific host discrimination, 2) mutual interference between females (extrinsic competition), 3) the outcome of multiparasitism (intrinsic competition), and 4) the effect of competition on host suppression. Our results showed that T. hyalinipennis females tended to probe repeatedly in the same hosts leading to longer host patch time and lower foraging efficiency. Both species avoided conspecific superparasitism, but not multiparasitism. When the two species foraged simultaneously, G. sp. nr. gonikopalense seemed to be slightly superior in extrinsic competition, while neither species seemed to have an advantage in intrinsic competition. Also, neither species could develop as a facultative hyperparasitoid, but they inflicted non-reproductive mortality on eggs containing 4-d-old larvae of their competitor. Lastly, host mortality inflicted by G. sp. nr. gonikopalense and T. hyalinipennis when acting together appeared to be additive. These results suggest that the presence of T. hyalinipennis in California is unlikely to reduce G. sp. nr. gonikopalense efficiency, but will instead improve the biological control of B. hilaris.

Life History and Rearing of Anastatus orientalis (Hymenoptera: Eupelmidae), an Egg Parasitoid of the Spotted Lanternfly (Hemiptera: Fulgoridae)

To support efforts to manage and contain spotted lanternfly (SLF), Lycorma delicatula White (Hemiptera: Fulgoridae), research is being conducted to develop classical biological control methods. To date, two potential biocontrol agents from China have been identified: an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae). The research detailed here focuses on investigating the biology and rearing of A. orientalis to assess its potential efficacy in a biocontrol program and optimize its rearing. Female wasps lived significantly longer than male wasps (68 and 23 d, respectively) and females produced an average of 94 total progeny that successfully emerged as adults, with most progeny produced between weeks one and four of the females' lives. The sex ratio of the progeny, with no re-mating, was initially highly female-biased but became progressively more male-biased, likely due to sperm depletion. There was no evidence of additional mortality to SLF eggs from wasp host feeding, but the data were highly variable and the sample size was small. There was high parasitoid emergence when oviposition conditions mimicked mid-September Beijing temperature and photoperiod; however, there was little emergence under 25°C and long-day conditions because most progeny entered a diapause. Storage of parasitized eggs in 5°C chill lowered parasitoid emergence rates. Lastly, there was no evidence that storing field-collected SLF egg masses in 5°C for 10 mo prior to parasitization affected parasitism rates. These findings inform our rearing protocol for A. orientalis and facilitate our testing of this species as a potential biological control agent for SLF.

Olfactory Reception of Host Alarm Pheromone Component by the Odorant-Binding Proteins in the Samurai Wasp, Trissolcus japonicus (Hymenoptera: Scelionidae)

The samurai wasp, Trissolcus japonicus, is the predominant egg parasitoid of the brown marmorated stink bug, Halyomorpha halys, in its native range in China. (E)-2-Decenal is a major component of the alarm pheromone of H. halys, an important invasive insect pest with significant economic importance. T. japonicus can be strongly repelled by (E)-2-decenal, and thus its host location efficiency would be reduced in the field. Better understanding on the molecular basis of olfactory reception of this host alarm pheromone component by T. japonicus may provide opportunities to develop novel approaches to enhance biological control efficacy of the parasitoid against H. halys. We identified six Odorant Binding Proteins (OBPs) from T. japonicus by transcriptome sequencing, within which three classical OBPs were expressed in a heterologous expression system with E. coli, harvested, and then challenged with (E)-2-decenal in binding assay experiments. TjapOBP2 showed the highest binding ability to (E)-2-decenal, compared to TjapOBP1 and TjapOBP3. Our results unambiguously suggest that TjapOBP2 would play an important role in discriminating (E)-2-decenal and could be a possible target for further intervention in the parasitoid-host system.

Side Effects of Organic Products on Telenomus podisi (Hymenoptera: Platygastridae)

Telenomus podisi Ashmead, 1893 is an important biocontrol agent, both in conventional and organic production systems. It can be used in association with other control strategies, such as natural botanical products and biological insecticides. Studies of selectivity and side effects are fundamental for proper management of insect control strategies because the interaction between different control strategies may negatively affect T. podisi. In this context, the present study evaluated the side effects of commercial natural products on T. podisi under laboratory conditions. Five natural products (insecticide, fungicide, and leaf fertilizer) allowed in organic farming were evaluated at concentrations recommended by the manufacturer in three bioassays. First bioassay (free-choice test), the preference of T. podisi parasitism between treated and non-treated E. heros eggs was assessed. In the second and third bioassay (no-choice tests) the treatments were applied to E. heros eggs, repectively before and after T. podisi parasitism (pre- and post-parasitism) and parasitism, emergence, offspring sex ratio, developmental time, and adult longevity were assessed. The products formulated with Metarhizium anisopliae (Metsch.) Sorok. (Hypocreales), Beauveria bassiana (Bals.) Vuill. (Hypocreales), orange oil fertilizer, and the fungicide copper oxychloride did not have side effects on T. podisi because they did not affect most of the evaluated characteristics. In contrast, azadirachtin A/B had a sublethal effect due to the reduced parasitism in all tests performed and, although it did not affect other aspects, this could compromise the performance of the parasitoid.

Effect of Temperature on the Survival and Developmental Rate of Immature Ooencyrtus mirus (Hymenoptera: Encyrtidae)

Bagrada hilaris (Burmeister) is an invasive pest of cole crops in the southwestern United States. To find potential biocontrol agents of B. hilaris, three egg parasitoids were imported from Pakistan, including Ooencyrtus mirus, a recently described uniparental species. We investigated the effect of temperature on survival and developmental rate in O. mirus from egg to adult. At 14 and 16°C, no adults emerged unless the immatures were transferred later to a warmer temperature. At constant 18°C, a low percentage emerged, but again more emerged if the immatures were transferred to a warmer temperature. Survival ranged from 80 to 96% at 20-37°C and did not differ significantly among these temperatures. No adults emerged at 38°C. Regardless of the amount of time the parasitized eggs were held at 14 and 16°C, the developmental times after returning the eggs to 26°C were similar, suggesting a quiescence process rather than simply slow development. At higher temperatures, the developmental rate increased linearly from 18 to 36°C and then declined at 37°C. The Wang model provided the best fit of the data and estimated a lower developmental threshold at 13.0°C, an optimal temperature at 35.6°C, and an upper developmental threshold of 38.3°C. The thermal constant for total immature development is 168.4 degree-days. The results show 36°C to be the best temperature for rearing O. mirus, and that O. mirus-parasitized eggs can be stored at 14°C for months without losing viability. These are crucial data to consider when mass rearing this biological control agent.

Effect of Temperature on Life History and Parasitization Behavior of Trichogramma achaeae Nagaraja and Nagarkatti (Hym.: Trichogrammatidae)

Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) is currently used as biological control agent for several lepidopteran pests. Knowledge of thermal requirements is essential to optimize its rearing procedures and inundative releases. The biological characteristics and two-sex life table parameters of T. achaeae were determined at five constant temperatures (15, 20, 25, 30, and 35 °C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. T. achaeae was able to develop and survive from 15 °C to 30 °C, but not at 35 °C. Temperature significantly affected the preadult development time and adult longevity, decreasing when temperature increased from 15 °C to 30 °C. Temperature significantly altered the sex ratio, being female biased between 15 °C and 25 °C. Age-stage, two-sex life table analysis indicated that net reproductive rate (R₀) was highest at 20 °C. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased with increasing temperature, while the mean generation time (T) decreased significantly. In addition, functional response of T. achaeae was studied, being significantly affected by temperature and host egg density, displaying a Holling type-I at 15 °C and a Holling type-II at 25 °C. The relevance of these results is discussed for the use of T. achaeae as biological control agent.

Egg parasitoids of Arboridia apicalis (Nawa, 1913) (Hemiptera, Cicadellidae), a leafhopper pest of grapevines in Japan, with description of a new species of Anagrus Haliday, 1833 (Hymenoptera, Mymaridae)

Several species of egg parasitoids (Hymenoptera: Mymaridae and Trichogrammatidae) of the leafhopper pest of grapevines in Japan, Arboridia (Arboridia) apicalis (Nawa) (Hemiptera, Cicadellidae), were reared and identified for the first time. Using a combination of genetic and morphological evidence, Anagrus (Anagrus) arboridiae Triapitsyn & Adachi-Hagimori, sp. nov. (Mymaridae) is described and illustrated from Honshu Island (Shimane Prefecture) and Kyushu Island (Miyazaki Prefecture). It is shown to be different from Anagrus (Anagrus) japonicus Sahad and A.flaviapex Chiappini & Lin, to which it is most similar; the latter species was originally described from China and is newly recorded here from Okinawa Island, Japan. Mitochondrial and nuclear ribosomal DNA sequence data provide clear evidence for the separation of A.arboridiae from A.flaviapex, A.japonicus, and some other members of the Anagrus (Anagrus) atomus (L.) species group. Two other species of Anagrus Haliday, A. (Anagrus) avalae Soyka and A.atomus, are also identified in Japan from eggs of the leafhoppers Edwardsianaishidae (Matsumura) and Eurhadina?betularia Anufriev, respectively. An updated key to females of the Japanese species of Anagrus is given. Oligositapallida Kryger (a new record for Japan), Oligosita sp., and an Aphelinoidea (Aphelinoidea) sp. (Trichogrammatidae) were the other, although much less abundant, apparent egg parasitoids of A.apicalis in Shimane Prefecture, mainly in non-organic vineyards.

Evaluation of the Physiological Host Range for the Parasitoid Ooencyrtus mirus, a Potential Biocontrol Agent of Bagrada hilaris

The thelytokous egg parasitoid Ooencyrtus mirus Triapitsyn and Power (Hymenoptera: Encyrtidae) was recovered from brassica plant debris in Pakistan in an effort to find a biological control agent of the invasive bug Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) in North America. As the first step in determining the overall host range of this parasitoid, adult females were exposed to the eggs of eight alternate pentatomid host species, two non-pentatomid heteropterans, and two lepidopterans, in choice and no-choice tests. Although O. mirus was more successful on B. hilaris than the other species in terms of the number of the eggs laid, the number of emerged progeny, and the developmental time of the progeny, it was able to reproduce on all of the alternate hosts except for one of the lepidopterans, whose eggs appeared too small for this parasitoid. The results show O. mirus to be a generalist parasitoid species with a preference for B. hilaris. The results also indicate that there is a linear relationship between the mean body length of O. mirus females and the mean host egg weight with an adjusted R 2 of 0.90. The implications of this study on the release of O. mirus for the control of B. hilaris are discussed.

Notes on the hosts of Trissolcus Ashmead (Hymenoptera: Scelionidae) from China

Background

Trissolcus Ashmead (Hymenoptera: Scelionidae) is a cosmopolitan genus of egg-parasitoid wasps associated with stink bugs (Pentatomidae, Scutelleridae, Urostylididae), many of which are important insect pests. Documentation of host associations for these wasps, which we here provide via museum specimens, can support their use as biological control agents of invasive stink bugs.

New information

The hosts of seven Trissolcus species are reported from China: Trissolcus cultratus (Mayr) (hosts: Hippotiscus dorsalis Stål, Pentatomidae; Urochela luteovaria Distant, Urostylididae), Trissolcus elasmuchae (Watanabe) (host: Niphe elongata (Dallas), Pentatomidae), Trissolcus japonicus (Ashmead) (hosts: Erthesina fullo (Thunberg), Pentatomidae; Rhaphigaster nebulosa (Poda), Pentatomidae), Trissolcus latisulcus (Crawford) (host: Poecilocoris latus Dallas, Scutelleridae), Trissolcus mitsukurii (Ashmead) (host: Pentatomidae), Trissolcus semistriatus (Nees von Esenbeck) (host: Eurydema sp., Scutelleridae), Trissolcus yamagishii Ryu (host: Niphe elongata (Dallas), Pentatomidae).

An Insight into the Role of Trissolcus mitsukurii as Biological Control Agent of Halyomorpha halys in Northeastern Italy

Sustainable strategies such as classical or augmentative biological control are currently being evaluated for the long-term management of the alien invasive pest Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). A three-year study carried out in northeastern Italy was performed to investigate the distribution and field performance of the H. halys egg parasitoid Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae), in comparison with other parasitoid species. In the study area, adventive populations of T. mitsukurii were present since 2016, representing the earliest detection of this species in Europe. Trissolcus mitsukurii was the most abundant parasitoid and showed a higher “parasitoid impact” (i.e., number of parasitized eggs over the total number of field-collected eggs) compared to the other species, i.e., Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae), Trissolcusbasalis (Wollaston) and Trissolcuskozlovi Rjachovskij (Hymenoptera: Scelionidae). The hyperparasitoid Acroclisoides sinicus (Huang and Liao) (Hymenoptera: Pteromalidae) was also recorded. Phylogenetic analysis of T. mitsukurii population distinguished two clades, one covering samples from Italy, Japan and China, the other from South Korea. The present study provides promising results for the biological control of a pest that is having a dramatic impact on a wide range of crops worldwide.

Impact of Temperature Storage Conditions of Halyomorpha halys (Hemiptera: Pentatomidae) Eggs on Parasitism by Anastatus reduvii (Hymenoptera: Eupelmidae)

Brown marmorated stink bug, Halyomorpha halys Stål, is an invasive species of Asian origin that is an important agricultural pest in the eastern United States. Sentinel egg masses are tools used to assess the impact of natural enemies on H. halys populations. To determine the effect of host egg age and storage conditions on their susceptibility to parasitism, H. halys eggs were stored at different temperatures for different lengths of time and then exposed to Anastatus reduvii (Howard), a native natural enemy of H. halys occurring in eastern North America. For eggs stored at 15, 20, and 25°C and then exposed to A. reduvii, the number of host eggs from which parasitoid offspring emerged declined with age of eggs. Control eggs (exposed to parasitoids without being stored) and those eggs stored for only 5.5 degree-days (DD) (=0.5 days) at 25°C yielded the highest percentage of parasitoids at 88.2 and 88.3%, respectively. For eggs stored at 20 and 25°C for 7.3 DD to about 36 DD, offspring emerged from about 58 to 73% of eggs, and total parasitism (emerged + unemerged parasitoids) ranged from about 70 to 80%. Parasitoid emergence was significantly lower for host eggs stored at 15°C for comparable times at 20 and 25°C. Stink bugs nymphs hatched from <0.6% of all eggs. Parasitoid-induced host egg abortion was an important component of egg mortality caused by A. reduvii, with underdeveloped stink bug nymphs, undifferentiated cell contents, and parasitoid host feeding occurring across all storage treatments.

Effect of the Ages of Parasitoid and Host Eggs on Telenomus podisi (Hymenoptera: Platygastridae) Parasitism

This study investigates the influence of parasitoid age and egg age of the hosts Euschistus heros (Fabricius) and Dichelops melacanthus (Dallas) on parasitism of Telenomus podisi Ashmead. Six separate bioassays were conducted: parasitism on eggs of E. heros (bioassay 1) and D. melacanthus (bioassay 2) by T. podisi females of different age (1, 5, and 10 days old); parasitism by T. podisi on eggs of different age (1, 2, 3, 4, and 5 days of embryonic development) of the hosts E. heros (bioassay 3) and D. melacanthus (bioassay 4); preference of T. podisi females for eggs at different embryonic developmental stages (eggs of 1, 2, 3, 4, and 5 days) of the hosts E. heros (bioassay 5) and D. melacanthus (bioassay 6). The age of T. podisi females and their hosts affected parasitism on both E. heros and D. melacanthus eggs. Overall, the parasitism rate was higher in older than younger parasitoids, independent of the tested host species, and host eggs between 1 and 3 days old were similarly parasitized. Thus, in T. podisi mass rearing facilities, it is recommended to use older adults (5 to 10 days old) as mother wasps to increase parasitism on the offered eggs. In addition, when hosts are completely absent in the field, or climatic conditions are unfavorable for release, mass-reared adults can be kept in the laboratory (25°C) for up to 10 days for later release in the field without any impairment of their subsequent parasitism performance.

Effect of Ephestia kuehniella (Lepidoptera: Pyralidae) Larval Diet on Egg Quality and Parasitism by Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

Trichogramma spp., among the most common parasitoids used for augmentation biological control, often are mass-reared on eggs of the Mediterranean flour moth, Ephestia kuehniella (Zeller). To evaluate removal of nutritional components from the E. kuehniella larval diet and reduce production costs, colonies were maintained using one of three diets: a standard diet consisting of eight ingredients, a reduced diet containing whole wheat flour, glycerol, and Brewer's yeast, or a third minimal diet of only whole wheat flour. The standard diet sustained the fastest larval development, female pupae with the greatest mass, the highest level of adult emergence, and production of the most eggs per female. Eggs from moths reared as larvae on the standard or reduced diet had equivalent mass, length, and percent hatch. Females from larvae fed the minimal diet produced eggs with the least mass that were shorter and had the lowest percent hatch. Eggs from the three E. kuehniella colonies were exposed separately to Trichogramma brassicae Bezdenko females to determine their acceptance for oviposition. More of the eggs from the standard diet were parasitized by the females, eggs from the reduced and minimal diets being less acceptable. The percent emergence of the parasitoids was the same regardless of diet; however, the largest wasps emerged from the standard diet eggs and a greater proportion of them were females. Consequently, the standard E. kuehniella larval diet resulted in the highest rate of reproduction and robust eggs that produced superior T. brassicae wasps.

Egg parasitoids of the tea green leafhopper Empoascaonukii (Hemiptera, Cicadellidae) in Japan, with description of a new species of Anagrus (Hymenoptera, Mymaridae)

Fairyfly (Hymenoptera, Mymaridae) egg parasitoids of the tea green leafhopper Empoasca (Matsumurasca) onukii Matsuda (Hemiptera, Cicadellidae), an economically important pest in Asia of the tea plant, Camelliasinensis, were identified from specimens reared in Japan. Using a combination of genetic and morphological evidence, Anagrus (Anagrus) rugmanjonesi Triapitsyn & Adachi-Hagimori, sp. n., is described and illustrated. It is shown to be different from the most similar A.turpanicus Triapitsyn & Hu, an egg parasitoid of a leafhopper pest of cultivated grapes which is known from Xinjiang Uyghur Autonomous Region in China. Mitochondrial and nuclear ribosomal DNA sequence data provide clear evidence for the separation of A.rugmanjonesi from A.turpanicus and other members of the Anagrusincarnatus Haliday species complex. A key to females of the Japanese species of Anagrus Haliday is given. Two other species of Mymaridae, Aresconenocki (Subba Rao & Kaur) and Stethyniumempoascae Subba Rao, are also identified, albeit the latter one only tentatively. Both latter taxa are newly recorded from Japan, and E.onukii represents their new host association.

Can Anastatus bifasciatus Be Used for Augmentative Biological Control of the Brown Marmorated Stink Bug in Fruit Orchards?

The generalist egg parasitoid Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae) is the most prevalent egg parasitoid of the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) in Europe. To assess its efficacy against the pest H. halys and to validate the potential risks for non-target species in a realistic field setting, inundative releases were conducted over three consecutive years in four fruit orchards in Switzerland and Italy. In total, more than 4300 A. bifasciatus females were released, which was equivalent to 11,000 to 26,000 females per hectare, depending on distances between trees in each orchard. Parasitism of freeze-killed sentinel H. halys eggs achieved with the current release strategy was on average 6% (range: 2%–16%) and considered not high enough to effectively suppress the pest. However, the overall impact of A. bifasciatus on the mortality of H. halys eggs was likely underestimated. If pre-imaginal parasitoid mortality (3.3%) and host feeding (6%) are added to the observed parasitism (6%), the actual induced mortality of H. halys eggs may reach more than 15%. Parasitism of lepidopteran non-target species reached an average of 8% and thus, some degree of non-target parasitism after mass releases may be expected. To quantify the impact of the parasitoids in the orchards more precisely, naturally laid egg masses should be used in future trials to include host-finding cues of the host and host plants, and larger scale releases with potentially higher densities of parasitoids should be considered.

n., an Egg Parasitoid of the Corn Leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) in the New World, and Anagrus incarnatus from the Palaearctic Region (Hymenoptera: Mymaridae)

The common New World egg parasitoid of the corn leafhopper Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae), an economically important pest of maize from Argentina to southern USA, has long been misidentified as the Palaearctic species Anagrus incarnatus Haliday or its synonym A. breviphragma Soyka (Hymenoptera: Mymaridae). Using a combination of genetic and morphometric methods, and available biological information, specimens reared from eggs of D. maidis in Argentina and Mexico, described and illustrated here as Anagrus (Anagrus) virlai Triapitsyn sp. n., are shown to be different from those of A. incarnatus from the Palaearctic region. Mitochondrial and nuclear ribosomal DNA sequence data provide clear evidence for the separation of the two species. Anagrus virlai is also known from Brazil, Colombia, Guadeloupe (France), and Guyana.

Different Oviposition Strategies of Closely Related Damselfly Species as an Effective Defense against Parasitoids

Parasitoidism is one of the main causes of insect egg mortality. Parasitoids are often able to detect eggs using semiochemicals released from eggs and disturbed plants. In response, female insects adopt a wide variety of oviposition strategies to reduce the detectability of eggs and subsequent mortality. We evaluated the proportion of parasitized and undeveloped eggs of three common damselfly species from the family Lestidae, the most diverse group of European damselflies, in terms of oviposition strategies, notably clutch patterning and the ability to utilize oviposition substrates with different mechanical properties. We assumed that higher costs associated with some oviposition strategies will be balanced by lower egg mortality. We found that the ability of Chalcolestes viridis to oviposit into very stiff substrates brings benefit in the form of a significantly lower rate of parasitoidism and lower proportion of undeveloped eggs. The fundamentally different phenology of Sympecma fusca and/or their ability to utilize dead plants as oviposition substrate resulted in eggs that were completely free of parasitoids. Our results indicated that ovipositing into substrates that are unsuitable for most damselfly species significantly reduces egg mortality. Notably, none of these oviposition strategies would work unless combined with other adaptations, such as prolonging the duration of the prolarval life stage or the ability to oviposit into stiff tissue.

Does Wolbachia Infection Change the Overwintering Ability of Trichogramma brassicae (Hymenoptera: Trichogrammatidae)?

The overwintering ability of a biological control agent helps predict potential survival and establishment in natural conditions. Here, we compared the overwintering ability in sexual and asexual Trichogramma brassicae Bezdenko, a key natural enemy of Lepidopteran pests in Iran over two consecutive winters in central Alborz Mountains. Our aim was to investigate the effect of Wolbachia infection on the overwintering rate of T. brassicae after emergence in the subsequent year. We also wanted to know whether there is any difference in the overwintering capacity of T. brassicae populations either in terms of exposure date or emergence date. Parasitized host eggs were exposed under outdoor conditions between 8 October and 27 November 2013 and between 8 October and 11 December 2014. Samples were checked weekly until adult emergence of overwintered individuals in the following spring, and proportion of adult emergence was recorded on each exposure date. Our results demonstrated that both populations were able to overwinter in natural conditions of central Alborz Mountains; however, sexual T. brassicae was more successful in overwintering than asexual one. No differences were observed in the emergence date and maximum emergence rate between two populations. Our study clearly identified a potential negative impact of Wolbachia on fitness of T. brassicae by a lower rate of emergence.