Native Parasitoids Research Articles

Potential side effects of the interaction between Phthorimaea absoluta parasitoids: the exotic Dolichogenidea gelechiidivoris and the native Bracon nigricans

The coexistence and efficiency in pest control of introduced and native parasitoids can be challenging. Continuous observations of the cohabitation of parasitoid species could confirm the persistence of the introduced parasitoid in the ecosystem under co-existence scenarios. This study provides an example of such a co-existence for biocontrol of the invasive pest, Phthorimaea absoluta (Meyrick) (Lepidoptera: Gelechiidae). Two parasitoids, the introduced endoparasitoid Dolichogenidea gelechiidivoris (Marsh) (Hymenoptera: Braconidae) and the native ectoparasitoid Bracon nigricans Szépligeti (Hymenoptera: Braconidae) were released in cages containing a tomato plant infested with P. absoluta. Parasitism and killing rate of P. absoluta by both parasitoid species, and the parasitoid and P. absoluta population were monitored weekly. The parasitoid species coexisted for seven weeks in the experimental units. Parasitism by D. gelechiidivoris was significantly affected by the presence of B. nigricans, with 73% and 22% parasitism in the absence and presence of B. nigricans, respectively. Parasitism by B. nigricans was not affected by its co-existence with D. gelechiidivoris. The number of D. gelechiidivoris adults increased eight-fold in five weeks in the absence of B. nigricans, while less than the initial number of adults were present in co-existence with B. nigricans. The P. absoluta infestation declined from the fifth week to 98% lesser than the control in all the treatments, either D. gelechiidivoris or B. nigricans as standalone treatments, as well as in combination. Since B. nigricans negatively affected D. gelechiidivoris population growth, releases of this introduced parasitoid should be considered with caution in areas where B. nigricans occurs.

Immature stages of Utetes anastrephae (Hymenoptera: Braconidae) developed in Anastrepha fruit fly larvae (Diptera: Tephritidae)

The morphology of the immature stages of Utetes anastrephae (Hymenoptera: Braconidae), a native parasitoid of larvae of flies of the Neotropical genus Anastrepha (Diptera: Tephritidae), is shown. This study aimed to characterize the immature stages and morphological changes in the development of the koinobiont endoparasitoid in two species of larval hosts, Anastrepha obliqua and Anastrepha ludens. The definition of structures and morphological changes during development was made through daily microscopic observations and photographs of dissected hosts. The immature development of the parasitoid corresponds to a holometabolous insect with three well-defined stages: egg (two days), larva with three larval instars (approximately eight days), and pupa (six days). Similar development times were obtained in the two host species. Males and females completed their cycle in 17 and 18 days, respectively. During egg-first instar development, host antagonistic activity through melanization and encapsulation as mortality factors was evident and frequent only in A. obliqua. These results serve as basic knowledge for the use of this parasitoid in the biological control of fruit flies.

Biological control potential of a laboratory selected generalist parasitoid versus a co-evolved specialist parasitoid against the invasive Drosophila suzukii.

A few generations of laboratory selection can increase the developmental success of native parasitoids on invasive targets. However, for this approach to be used more widely for biological control, we need to understand if the improved performance of native species, achieved under artificial laboratory conditions, translates to improved control in more natural environments. It is also unknown what the biocontrol potential of laboratory selected generalist native parasitoids may be compared to co-evolved specialists that are typically introduced for biological control of invasive species. To assess how rearing in artificial diet affected host finding ability in natural hosts, we used laboratory selected (adapted) and nonadapted populations of the generalist native parasitoid Trichopria drosophilae to parasitize the invasive fly, Drosophila suzukii in three different fruit types. In a separate experiment, we compared the effectiveness of adapted and nonadapted populations of T. drosophilae in raspberries with a co-evolved specialist larval parasitoid Ganaspis brasiliensis from Asia that was recently approved for release in the USA. More adult parasitoids emerged in each fruit type of the adapted compared to the nonadapted population of T. drosophilae. D. suzukii emergence rates were reduced on average by 85% by the adapted T. drosophilae population indicating that the artificial rearing conditions did not significantly impair the ability of parasitoids to locate and attack hosts in natural hosts. The specialist G. brasiliensis had higher adult emergence than the adapted population of T. drosophilae; however, both parasitoid species were able to reduce D. suzukii populations to the same extent. These results show that despite the lower developmental success of the laboratory selected T. drosophilae, they killed the same proportion of D. suzukii as G. brasiliensis when host choice was restricted. In nature, where host choices are available, specialist and generalist parasitoids will be unlikely to exhibit the same biocontrol potential.

Field releases of the exotic parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae) and survey of native parasitoids attacking Halyomorpha halys (Hemiptera: Pentatomidae) in Michigan.

An adventive population of the exotic parasitoid wasp, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), discovered in Michigan in 2018, is a promising biological control agent of the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Following its discovery, field releases of Tr. japonicus were conducted over 2 yr in southern Michigan, to test how release size or release frequency impacts establishment. Sentinel eggs of H. halys and of the native Podisus maculiventris (Say) (Hemiptera: Pentatomidae) were used alongside yellow sticky cards to monitor parasitoids. In 2019 and 2020, 7,200 Tr. japonicus were released at 16 sites. Monitoring between 2019 and 2021 yielded only 49 individuals. The captures suggest reproductive activity and overwintering success in the field but do not allow for evaluation of best release methods. Parasitism by native parasitoids was below 7%, which is similar to other states and unlikely to provide sufficient control of H. halys. The placement of sentinel eggs or sticky traps either in the lower or middle canopy of trees did not influence parasitoid capture rates. Frozen and fresh H. halys sentinel eggs were attacked at the same rate, but more native parasitoids emerged from frozen eggs. We did not find signs of nontarget effects on P. maculiventris thus parasitism rates overall were very low. These results could indicate dispersal of Tr. japonicus from the release sites or slow population growth. The latter may be due to the relatively low densities of H. halys in Michigan or may stem from the small founding size of our laboratory colony.

SOME BIOTIC LIMITING FACTORS OF DRYOCOSMUS KURIPHILUS (HYMENOPTERA CYNIPIDAE): A SURVEY IN CHESTNUT ORCHARDS NEAR FLORENCE (ITALY)

The biological control of the Asian Chinese gall wasp (ACGW) Dryocosmus kuriphilus, is influenced by several factors. In 2013, a survey was carried out in three chestnut orchards near Florence (Italy) to investigate ACGW parasitization by native parasitoids and the introduced Torymus sinensis. The following two methods were adopted: the first based on the dissection of cynipid galls with the aim of inspecting cells within each gall and the second based on monitoring adult emergence from galls. Parasitization patterns due to gall position related to plant height were also evaluated. Native parasitoids were more abundant in the upper part of tree crowns in June, while in July and August their activity was more evident in the middle and lower parts of chestnut trees. Conversely, parasitization of T. sinensis, was detected at all plant heights. Plant position within stands also affected the performance of both native parasitoids and T. sinensis, with parasitization that progressively decreasead moving toward the interior of the orchards. Gall necrosis was equally evaluated as a limiting factor of ACGW survival. Among the isolated fungal species, Gnomoniopsis castaneae (Tamietti), an endophyte fungus harmful to fruits, colonized both healthy and necrotic galls together with ubiquitous components of fungal communities such as Alternaria sp., Aspergillus sp., Fusarium sp. and Colletotrichum fioriniae. Our results evidenced that T. sinensis was able control the ACGW, while native parasitoids played only a secondary, though non-negligible, role. Conversely, gall necroses had a minor impact on pest control, as their efficacy was limited to the early stages of gall development. Key words: biodiversity, gall-inducing insects, native parasitoids, fungal species

Native Hymenopteran parasitoids associated with fruit flies (Diptera: Tephritidae) in fruits and vegetables in three ecological zones of Togo

Fruit flies (Diptera: Tephritidae) are major pests associated with fruit and vegetable production in West Africa in general and in Togo in particular. The use of parasitoid wasps to significantly reduce their populations in agroecosystems is a significant component of the integrated management of these pests (IPM-package). To do this, it is important to know their diversity, distribution and potential in controlling fruit flies. In this perspective, the incubation of 28 species of fruits and vegetables sampled in 2009 in ecological zones III, IV and V in Togo allowed to identify five species of native braconid parasitoids: Fopius caudatus Szepligeti, Diachasmimorpha fullawayi Silvestri, Bracon sp., Fopius sp. and Psyttalia sp. F. caudatus was the most abundant making 98.6% of parasitoids recovered. These parasitoids were associated with 4 species of fruit flies, the most abundant being the native species, Ceratitis cosyra (Walker). The parasitism rate in the three ecological zones depended on the locality, the incubated fruit and the fruit fly species. It was relatively low and ranged from 0 to 42.31%, with the highest average rate recorded in the wild fruit, Sarcocephalus latifolius (Sm.) E.A.Bruce, associated exclusively with C. cosyra. Pupae recorded from S. latifolius frequently yielded F. caudatus which was the most abundant. Assessment of the demographic parameters of F. caudatus, a potential candidate for augmentative biological control of C. cosyra in Togo, should be considered under controlled and natural conditions.

Eriogynapyretorum (Lepidoptera, Saturniidae) parasitoid species investigated in Fujian, China.

Eriogynapyretorum Westwood is a notorious defoliator of Camphoraofficinarum Nees that causes large economic and ecological losses in planted forests. To understand the importance of suppressing the population of E.pyretorum on natural parasitoids, a four-years investigation was conducted in the field. Four egg parasitoid species Ooencyrtuskuvanae Howard, Trichogrammachionis Ishii, Telenomus sp. and Anastatusdexingensis Sheng & Wang were captured in the wild. One of these is the dominant endoparasitoid species T.chionis, which has a quicker developmental time (8.33 d), more offspring (8.39/egg) and a greater parasitism rate (89.54%). With different elevation distributions, the parasitism rates for Kriechbaumerellalongiscutellaris Qian & He, Gregopimplahimalayensis (Cameron), Theroniadepressa (Gupta) and Xanthopimplakonowi (Krieger) were 17.29%, 2.10%, 4.23% and 0.83%, respectively. Female longevity (47.75 d), offspring (13.36/pupa) and sex ratio (1.16:1) were compared in four pupal parasitoids and K.longiscutellaris was the most abundant species of E.pyretorum in Fujian Province.

An Egg parasitoid, Mirufens Girault (Hymenoptera: Trichogrammatidae) Reared from Oxyrachis tarandus Fab. Attacking on Cassia fistula L. (India)

Cassia fistula L. is known as Golden shower or Amaltas has therapeutics importance in health care since ancient times. It shows a pivotal role in diseases prevention due to their valuable ingredients in different parts of plants. One of known hemipterous insect pest, attacking on this valuable tree is Oxyrachis tarandus Fab. (Hemiptera: Membracidae), its nymphs and adults feed gregariously on the sap of the shoot of host plant results in the stunting or death of the infested shoot. Oxyrachis tarandus population may be checked by some natural parasitoids. Mirufens Girault is one of important egg parasitoid recorded on this hemipterous insect pest, attacking on different host plants. In the present study, we are recorded egg parasitoid M. afrangiata from the eggs of Oxyrachis tarandus, infesting Cassia fistula plant for the first time. Re-described and illustrated two species of the genus Mirufens; M. afrangiata and M. brevifuniculata along with first male record of M. brevifuniculata. An updated key to the Indian species of Mirufens are also provided

Exploration for native parasitoids of Asian longhorned beetle in China as prospective biological control agents

Abstract Native to China and the Korean Peninsula, the Asian longhorned beetle (ALB) Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) is a high‐risk invasive pest of hardwood trees. To explore the potential of biological control of ALB in the United States, we conducted surveys of ALB parasitoids using sentinel logs in five geographical regions (Beijing, Gansu, Guizhou, Shanghai, and Yunnan) in China from 2019 to 2022. Seven hymenopteran larval parasitoid species, Bracon planitibiae Yang, Eurytoma chinensis Yang, Heydenia sp., Oxysychus glabripennis Yang, Sclerodermus guani Xiao et Wu, Spathius anoplophorae Yang, and Zolotarewskya anoplophorae Yang, were collected in Beijing. Four, three and two of these species were also found in Shanghai, Guizhou, and Yunnan, respectively. No parasitoid was found in Gansu. Mean parasitism rates by all parasitoid species were 3.6%–15.8% in Beijing, 1.4%–16.4% in Guizhou, 1.6%–7.1% in Shanghai, and 5.8% in Yunnan. Spathius anoplophorae and O. glabripennis were the two most dominant parasitoids collected consistently in the four different regions and may be considered as prospective agents for biological control introduction against ALB in the United States. We discuss some underlying ecological mechanisms that might contribute to the rarity of egg parasitoids and future opportunities and challenges for biological control of ALB.

Factors affecting distribution of emerald ash borer parasitoids in an urban environment

Invasive woodboring insects such as emerald ash borer (EAB), Agrilus planipennis, cause significant economic and environmental harm to both traditional and urban forests. Hymenopteran biological control agents were introduced to North America for protection of non-insecticide treated ash trees. Urbanization is known to impact arthropod abundance, richness, and services, and yet few studies specifically examine biocontrol agent distribution or services within urban environments. While EAB biocontrol agents are successfully establishing in traditional forests, it is not known whether urban forests are sufficiently hospitable for their establishment and persistence. In this study, we investigate how urban land cover impacted both the establishment and distribution of introduced biocontrol agents and the presence of EAB-associated endemic native parasitoids. Over the three year study period we detected a persistent negative impact of urbanization on presence of two parasitoids, the introduced Spathius galinae and native Atanycolus spp, while another native, Phasgonophora sulcata, was only negatively impacted by urbanization in the first sampling year. Presence of the introduced Tetrastichus planipennisi was negatively correlated with tree size, but not urbanization. Presence of all parasitoids was greater on trees with declining canopy health. This study indicates that while some parasitoids appeared to be negatively affected by urbanization, biological control agents of EAB successfully established and are generally widely distributed in Syracuse, NY.

First record of Telenomus turesis (Walker), native egg parasitoid of invasive brown mamorated stink bug [Halyomorpha halys Stal (Hemiptera: Pentatomidae)] in Turkey

Halyomorpha halys (Hemiptera: Pentatomidae) Doğu Asya (Çin, Japonya, Kore ve Tayvan) kökenli bir türdür ve doğal yaşam alanlarında önemli bir polifag zararlı olup, yayılış gösterdiği alanları kısa zaman içerisinde yüksek bir popülasyon meydana getirerek istila etmekte ve tarımsal üretim için önemli bir tehdit oluşturmaktadır. Türkiye’de özellikle Karadeniz sahil şeridi boyunca yayılış gösterdiği alanlar içerisinde başta fındık olmak üzere pek çok üründe önemli kalite ve verim kaybına sebep olabilir. Bu çalışma, Sakarya’da farklı habitatlarda H. halys'in yerli yumurta parazitoitlerini ve bu türlerin etkinliklerini belirlemeyi amaçlamaktadır. Bu amaçla, arazi şartlarında elde edilen bir günlük yaştaki 20 yumurta paketi (600 yumurta) 9 farklı lokasyonda farklı bitkilere asılmış ve 4 gün sonra toplanarak laboratuvara getirilmiştir. Toplanan yumurtaların genel parazitlenme oranı %7,5 olmasına rağmen, bu yumurtalardan başarılı bir şekilde yalnızca üç parazitoit çıkışı meydana gelmiştir. Morfolojik olarak teşhisleri yapılan bu parazitoitler, sitokrom c oksidaz alt birim I genine (CO1) dayalı moleküler teşhis ile doğrulanarak, Telenomus turesis (Walker) olduğu belirlenmiştir. H. halys’in yerli yumurta parazitoit türü, bu çalışma ile Türkiye’de ilk kez rapor edilmektedir. Bu kapsamda istilacı türün ülkemizde yayılış gösterdiği alanlarda doğal düşman faunasının araştırılması, mücadele için önemli aşamalardan birisi olup daha fazla araştırmaya ihtiyaç duyulmaktadır. Ek olarak, uzun vadeli sürdürülebilir yaklaşım olan klasik biyolojik mücadele kapsamında, ithalatı gerçekleştirilen Trissolcus japonicus (Ashmead)’un hızlı ve kontrollü bir şekilde kitlesel üretimine geçilmesi ve salımı yüksek derece önem arz etmektedir.

Cowpea extrafloral nectar has potential to provide ecosystem services lost in agricultural intensification and support native parasitoids that suppress the wheat stem sawfly.

The native parasitoids Bracon cephi (Gahan) and B. lissogaster Muesebeck (Hymenoptera: Braconidae) reduce populations of Cephus cinctus Norton (Hymenoptera: Cephidae), a native grassland species, and major wheat pest on the Northern Great Plains of North America. Non-host feeding adults of these braconids increase longevity, egg load, and egg volume when provisioned carbohydrate-rich diets. Nutrition from nectar can enhance the success of natural enemies in pest management programs. Cowpea, Vigna unguiculata (L.) Walpers, is a potential cover-crop that could add resilient features to the landscape and has extrafloral nectaries (EFN), easy-access nectar sources for beneficial insects. If more cowpea was grown on the Northern Great Plains, would B. cephi and B. lissogaster benefit from foraging on putatively beneficial EFN? We investigated cowpea inflorescence stalk extrafloral nectars (IS-EFN) and leaf stipel extrafloral nectars (LS-EFN) as potential food sources for these parasitoids. Females were caged on EFN sources on living cowpea plants to assess longevity. Egg load and volume were measured at 2, 5, and 10 days after placement. Bracon cephi survived 10 days on water, 38 days on IS-EFN; B. lissogaster 6 days on water, 28 days on IS-EFN. Bracon lissogaster maintained a constant egg load and volume across treatments while B. cephi produced 2.1-fold more eggs that were 1.6-fold larger on IS-EFN. Y-tube olfactometry indicated adult females were attracted to airstreams containing cowpea volatiles. These results demonstrate that non-native, warm-season cowpea benefits these native parasitoids and may improve conservation biocontrol of C. cinctus.

Covert infection with an RNA virus affects medfly fitness and the interaction with its natural parasitoid Aganaspis daci

AbstractWith the advent of high-throughput sequencing, large sets of insect-infecting RNA viruses producing apparent asymptomatic infections are being discovered. In the Mediterranean fruit fly (medfly) Ceratitis capitata, an agricultural key pest of a wide range of fruits, 13 different RNA viruses have been described so far. Recent analysis demonstrated a wide distribution of these viruses in different medfly strains collected worldwide, but little is known about the interactions between those viruses and the medfly host. Previous studies suggested that a higher abundance of Ceratitis capitata nora virus (CcaNV) correlated with a shorter lifespan in adults. Here, we investigated the effect of CcaNV on a broad range of parameters related to host fitness and its interaction with other trophic levels. CcaNV purified from a naturally infected medfly strain was added to the larval diet. Pupal weight, adult emergence, flying ability, and longevity were monitored after oral infections. Our results revealed detrimental effects associated with a CcaNV infection in the medfly, in terms of reduced pupal weight and reduced adult longevity. Moreover, we tested the influence of a CcaNV infection in medflies on the parasitism performance of Aganaspis daci, an endoparasitoid used in biological control programs against medflies. Our results showed that A. daci progeny increased when parasitizing on CcaNV-infected larvae. Overall, we proved that covert RNA viruses can impact the insect ecology, directly affecting its insect host biology and indirectly influencing multitrophic interactions.

Lethal and sublethal effects of toxic bait formulations on Doryctobracon areolatus (Hymenoptera: Braconidae) and implications for integrated fruit fly management.

The use of toxic baits has become one of the main methods of management of fruit flies in Brazil. The application of toxic baits may cause side effects on the native parasitoid Doryctobracon areolatus (Hymenoptera: Braconidae). Based on the results, formulations made from the food attractants 3% Biofruit, 1.5% Ceratrap, 1.25% Flyral, 3% Isca Samaritá, 3% Isca Samaritá Tradicional, and 7% sugarcane molasses associated with the Malathion 1000 EC and the ready-to-use toxic bait Gelsura (containing the active ingredient alpha-cypermethrin) were classified as harmful (class 4) to D. areolatus (mortality > 85% at 96 HAE). In contrast, for toxic baits formulated with insecticide phosmet, the mortality ranged from 38% to 72%, classified as slightly harmful or moderately harmful. However, when phosmet was added to the 3% Samaritá Tradicional bait, the mortality was only 3.9% (class 1-harmless), similar to the toxicity observed for the Success 0.02 CB ready-to-use bait (0.24 g a.i. spinosad/l) (<5% mortality). Although toxic baits were formulated with spinosyn-based insecticides, all toxic bait formulations were classified as harmless or slightly harmful (<50% mortality) to D. areolatus, with the exception of 1.5% Ceratrap + spinetoram and 7% Sugarcane molasses + spinosad (≈ 60% mortality-moderately harmful). In addition, these formulations did not show sublethal effects in reducing the parasitism and emergence rate of the F1 generation of D. areolatus in A. fraterculus larvae. The results serve as a basis for the correct use of toxic food baits without affecting the biological control.

Population level interactions between an invasive woodwasp, an invasive nematode and a community of native parasitoids

Parasitic nematodes and hymenopteran parasitoids have been introduced and used extensively to control invasive Eurasian Sirex noctilio woodwasps in pine plantations in the Southern Hemisphere where no members of this community are native. Sirex noctilio has more recently invaded North America where Sirex-associated communities are native. Sirex noctilio and its parasitic nematode, Deladenus siricidicola, plus six native hymenopteran woodwasp parasitoids in New York and Pennsylvania, were sampled from 204 pines in 2011–2019. Sirex noctilio had become the most common woodwasp in this region and the native parasitoids associated with the native woodwasps had expanded their host ranges to use this invader. We investigated the distributions of these species among occupied trees and the interactions between S. noctilio and natural enemies as well as among the natural enemies. Sirex noctilio were strongly aggregated, with a few of the occupied trees hosting hundreds of woodwasps. Nematode parasitism was positively associated with S. noctilio density, and negatively associated with the density of rhyssine parasitoids. Parasitism by the parasitoid Ibalia leucospoides was positively associated with host (S. noctilio) density, while parasitism by the rhyssine parasitoids was negatively associated with density of S. noctilio. Thus, most S. noctilio come from a few attacked trees in a forest, and S. noctilio from those high-density trees experienced high parasitism by both the invasive nematode and the most abundant native parasitoid, I. l. ensiger. There is little evidence for direct competition between the nematodes and parasitoids. The negative association occurring between rhyssine parasitoids and I. l. ensiger suggests rhyssines may suffer from competition with I. l. ensiger which parasitize the host at an earlier life stage. In addition to direct competition with the native woodwasp Sirex nigricornis for suitable larval habitat within weakened trees, the large S. noctilio population increases the parasitoid and nematode populations, which may increase parasitism of S. nigricornis.

Evaluation of the Community Structure Leafminer Fly, Liriomyza spp. (Diptera: Agromyzidae) and Their Parasitoids on Various Host Plant Families in Bali Province

Leaf miners, Liriomyza spp., have developed as a severe pest in recent years, reducing the production of several ornamental and crops in Indonesia. As a result, monitoring and control mechanisms have been proposed. This research aimed to investigate community structure and identify Liriomyza spp., which impacts crops and natural parasitoids in Bali Province. Leaf samples of vegetables, ornamental plants, and related species were collected in all regencies/cities of Bali Province in 2019 and 2020 and preserved in the laboratory for observation and counting of leaf miners and related parasitoids. The findings revealed that four Liriomyza spp. were detected in host plants, namely Liriomyza sativae Blanchard (Diptera: Agromyzidae), Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae), Liriomyza chinensis Kato (Diptera: Agromyzidae), and Liriomyza trifolii Burgess (Diptera: Agromyzidae). Asteraceae species were the most common host plants attacked by leaf miners in the field. The same occurrence was discovered at both heights (high and lowlands). The dry season is the most crucial component in the abundance of Liriomyza spp. In addition, parasitoids of the type Opius cromatomiyae Belokobylskij and Wharton (Hymenoptera: Braconidae) and Hemiptarsenun varicornis Girault (Hymenoptera: Eulophidae) were identified in abundance in Asteraceae plants. Similarly, the parasitization rate of the two parasitoids was found to be high in plants of the Asteraceae and Brassicae families. This approach highlights the decision-making process for controlling Liriomyza spp. on diverse host plant families by developing ecologically beneficial and sustainable parasitoids.

Adventive Population ofTrissolcus japonicus(Hymenoptera: Scelionidae), Parasitoid ofHalyomorpha halys(Hemiptera: Pentatomidae), Discovered in Southwestern Idaho

AbstractAdventive populations of Trissolcus japonicus (Ashmead) have been detected in the eastern and western United States including the western states of Washington, Oregon, California, and Utah. These populations may provide classical biological control for the invasive brown marmorated stink bug, Halyomorpha halys (Stål), which can cause economic loss to many specialty crops in western North America. Idaho has not previously been surveyed for the exotic T. japonicus or native parasitoids of H. halys. In July 2021, T. japonicus was discovered emerging from wild H. halys egg masses in Star, Idaho (43.69788, −116.49427), and was detected on yellow sticky cards from July to September. This is the first record of T. japonicus in the state of Idaho. T. japonicus constituted only a small portion of Trissolcus species detected; other species included T. euschisti (Ashmead), T. hullensis (Harrington), and T. utahensis (Ashmead). Genetic population level analysis of T. japonicus specimens from Idaho supports the likelihood of its expansion inland from the west coast, inhabiting ecozones previously considered unsuitable due to high temperatures and low humidity. This report opens the prospect of an effective biological control agent for H. halys in Idaho and potentially other hot and dry geographic regions and expands documentation of the presence of adventive T. japonicus populations in North America.

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.

The parasitic complex of Halyomorpha halys: preliminary data on adaptation of native egg parasitoids to the invasive host

The parasitic complex of <i>Halyomorpha halys</i>: preliminary data on adaptation of native egg parasitoids to the invasive host

Limited gains in native parasitoid performance on an invasive host beyond three generations of selection.

Co-evolved natural enemies provide sustainable and long-term control of numerous invasive insect pests, but the introduction of such enemies has declined sharply due to increasing regulations. In the absence of co-evolved natural enemies, native species may attack exotic invasive pests; however, they usually lack adaptations to control novel hosts effectively. We investigated the potential of two native pupal parasitoids, Pachycrepoideus vindemmiae and Trichopria drosophilae, to increase their developmental success on the invasive Drosophila suzukii. Replicated populations of the two parasitoids were subjected to 10 generations of laboratory selection on D.suzukii with Drosophila melanogaster serving as the co-evolved host. We assessed developmental success of selected and control lines in generations 0, 3, and 10. Changes in host preference, sex ratio, development time, and body size were measured to evaluate correlated responses with adaptation. Both parasitoid species responded rapidly to selection by significantly increasing their developmental success on the novel host within three generations, which remained constant for seven additional generations without further improvement. The generalist parasitoid species P.vindemmiae was able to reach similar developmental success as the control populations, while the performance of the more specialized parasitoid T.drosophilae remained lower on the novel than on the co-evolved host. There was no increase in preference towards the novel host over 10 generations of selection nor were there changes in development time or body size associated with adaptation in either parasitoid species. The sex ratio became less female-biased for both parasitoids after three generations of selection but rebounded in P.vindemmiae by generation 10. These results suggest that a few generations of selection may be sufficient to improve the performance of native parasitoids on invasive hosts, but with limits to the degree of improvement for managing invasive pests when exotic co-evolved natural enemies are not available.