Parasitism Rates Research Articles

EFFECTS OF RELEASES OF THE EGG PARASITOIDS GRYON FULVIVENTRE CRAWFORD (HYMENOPTERA: SCELIONIDAE) ON CLAVIGRALLA TOMENTOSICOLLIS STAL. (HEMIPTERA: COREIDAE), A COWPEA POD-SUCKING BUG, IN A CONTROLLED ENVIRONMENT

Clavigrallatomentosicollis Stal. (Hemiptera: Coreidae), major cowpea pod-sucking bug, causes significant economic losses. In the search for an alternative to chemicalcontrol, the use of the egg parasitoid G. fulviventre is a possibility. Given that no release strategy for G. fulviventre has yet been tested, it would seem wise, before considering large-scale use of this parasitoid, to determine an optimum release frequency. The mainof this study is to find an optimal frequency of parasitoid release. To this end, artificial infestations were carried outin a semi-controlled environment at the Centre for Environmental, Agricultural Research and Training of Kamboinse (Burkina Faso). A single release of the pest was carried outwith five release frequencies of the parasitoid. The results showed that the rate of parasitism was higher (64.57 ±4.76%) in successive releases of the parasitoid spaced one week apart and lower (42.72 ±4.99 %)in the single release.Pods were almost completely damaged without parasitoid release (91.83±1.74 %) and less damaged with successive releases (24.58 ± 1.59%). Parasitism rates did not differ significantly between two, three or four successive releases. This study is a first on the release of G. fulviventre in Burkina Faso and the results are of great importance for the implementation of an integrated management strategy of C. tomentosicollis.

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.

Making of the "Pristine Vegetables": Soil-Transmitted Parasites and U.S. Military Procurement in Korea.

In the twenty-first century Korea, "Pristine Vegetables(청정채소)" refers to organic products grown without the use of pesticides and chemical fertilizers. However, the meaning of "Pristine" was radically different until 1970s. After the Korean War, the infection rate of intestinal parasite reached almost 100 percent in Korean population. Disruption in chemical fertilizers manufacturing pressured farmers to use night-soil, which was contaminated with parasite eggs, causing the vicious cycle of infection. At the same time, rapid urbanization increased the demands of fresh vegetables in the city, leading to a large amount of semi-urban agricultural practices. This was closely linked with the national economy; as most of Korean vegetable products were contaminated with parasites, they were deemed unsuitable for export. In 1957, US Army stationed in Seoul issued a guideline for producing local vegetables acceptable for US troop consumption. This gave rise to the concept of "Pristine Vegetables" that were free of any infectious materials. These practices continued well into the 1970s. Due to the lack of sewage treatment system, the waste of urban population provided necessary fertilizer for these farmers without much cost. In order to secure public health, the Korean government actively encouraged the use of chemical fertilizers, naming the vegetables "Pristine." This effort included the ban of night-soil in urban and semi-urban farms and the establishment of Pristine Vegetable Shops. However, the rapid decline of parasitic diseases in the population and the rising concerns of environmental pollutions reshaped Pristine Vegetables from chemical to organic in the 1980s. Thus, Pristine Vegetable in Korea during late twentieth century exemplifies rapid transformation of the urban environment, showing shifted concept of cleanness and contaminants among the public and policymakers, as well as acceptable risk of the urban environment in Korea.

Substantial fitness costs in terms of parasitization rates, offspring production and sex ratio of Wolbachia infection in Nasonia vitripennis without modified host preference

Abstract Wolbachia is a genus of endosymbiotic bacteria that is widespread among arthropods. It is responsible for manipulating various host phenotypes and often affects their host's fitness. We used the generalist parasitoid wasp Nasonia vitripennis and its endosymbiont Wolbachia to test whether and how Wolbachia affects the fitness of N. vitripennis by comparing the host preference and parasitization rate of cured and uncured N. vitripennis lines. We reared four genotypes of wasps, each with Wolbachia infection or cured of infection, using two different host species, namely Calliphora vomitoria and Lucilia sericata, for 3–4 generations before measuring their host preference because rearing history has previously been shown to influence host preference in N. vitripennis. We found that all experimental groups significantly preferred C. vomitoria pupae. Neither rearing history nor Wolbachia infection altered N. vitripennis female's innate host preference. Furthermore, we investigated whether Wolbachia infection may affect Nasonia's parasitization rate, offspring production and sex ratio using parasitization assays of two wasp genotypes with and without Wolbachia infection. Our results show that uncured wasps have fitness costs of harbouring Wolbachia in terms of reduced parasitization rate and offspring production in one of the host genotypes and reduced proportion of female offspring in the second host genotype tested, highlighting the context‐dependency of host–endosymbiont relationships.

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.

Spatial and temporal dynamics of soybean gall midge (Resseliella maxima) parasitism by Synopeas maximum.

Soybean gall midge, Resseliella maxima Gagné (Diptera: Cecidomyiidae), is a pest that impacts soybean yield in the Midwest United States. While biological control using parasitoids may be a promising approach for managing this pest, it is crucial to have a deep understanding of parasitism dynamics to ensure effective implementation. We investigated R. maxima parasitism using a combination of three methods: rearing of field-collected hosts, dissection, and molecular assays. We confirmed parasitism of R. maxima by the recently described wasp Synopeas maximum Awad & Talamas (Hymenoptera: Platygastridae) and used our combinatorial approach to observe the spatial and temporal relationships between R. maxima and its parasitoid in the field. The number of R. maxima adults was greater in symptomatic plants on field edges than the field interior, but such a pattern was inconsistent for parasitism rates. Parasitism rates were generally highest early and late in the season, and lower in the middle of the season when the number of R. maxima was highest. In Minnesota, overall season-long parasitism rates of R. maxima were low (< 2%). To facilitate a wider investigation of the biological control of R. maxima, we designed a protocol for high throughput DNA extraction and quantitative polymerase chain reaction (qPCR) that can be used across a broader geography. Further research should evaluate how parasitism rates by Synopeas maximum could be promoted in production fields. © 2023 Society of Chemical Industry.

Study on the field propagation of Pteromalus sanjiangyuanicus Yang and its biological control of Gynaephora qinghaiensis

Gynaephora qinghaiensis is an important pest that damages alpine meadow vegetation in Qinghai-Tibet Plateau (QTP) alpine pastoral areas. Pteromalus sanjiangyuanicus Yang is a parasitic natural enemy of pupal G. qinghaiensis. For biological control of G. qinghaiensis, local materials and G. qinghaiensis were used for P. sanjiangyuanicus propagation. Under natural field conditions, P. sanjiangyuanicus were propagated in artificial nests. Propagated P. sanjiangyuanicus were then released into the experimental area, where the G. qinghaiensis density was high, and the biological control effect was evaluated. In the propagation test plot (D), the average P. sanjiangyuanicus parasitism rate was 70.3% (46.3–87.0%). The P. sanjiangyuanicus parasitism rate in the experimental area was significantly higher than that in the control area, and the propagation effect was good. The P. sanjiangyuanicus parasitism rates in the biological control plots (A, B, and C) increased yearly from 2016 to 2019, indicating that the P. sanjiangyuanicus population size in the biological control area increased yearly and that the parasitoid population size effectively increased. From 2016 to 2019, the G. qinghaiensis population decline rates in the biological control plots (A, B and C) were 71.1%, 59.3% and 76.4%, respectively (average 68.9%). The control effects on G. qinghaiensis were 80.9%, 69.9% and 80.3%, respectively (average 77.0%). The results showed that P. sanjiangyuanicus was effective in controlling G. qinghaiensis. This study provides a reference for the large-scale propagation of P. sanjiangyuanicus and the further promotion and application of G. qinghaiensis biological control.

Epidemiological Surveillance of Hypodermosis in Cattle from Romania.

Hypodermosis, or warble fly, is an endemic parasitic disease, common in countries from the northern hemisphere. The use of effective insecticides has decreased the frequency of this parasitic disease, with untreated cattle remaining to act as reservoirs. This study focused on assessing the status of hypodermosis in northwestern Romania by means of clinical examination (skin inspection and palpation performed in order to identify nodules) conducted on a number of 11.741 cattle. The study was carried out from March until June 2021. The identified larvae were subject to molecular assays for species identification and genotyping, followed by comparison with data available in the GenBank database. The average prevalence rate of parasitism caused by Hypoderma spp. was 0.31%, with values ranging from a minimum of 0.11% to a maximum of 1.32%. The dominant age group among positive animals was the 1-3 years old category and in terms of breed distribution, most positive cases were seen in cows belonging to an indigenous breed: Bruna de Maramures. April was the most prolific month in terms of nodule count/animal. The species identified in our study by means of molecular assays was H. bovis with two haplotypes: HB3 and HB8.

Interactions between egg parasitoids and predatory ants for the biocontrol of the invasive brown marmorated stink bug Halyomorpha halys

AbstractThe brown marmorated stink bug Halyomorpha halys is an Asian species that has become a major agricultural pest in North America and Europe. Ants from the genus Crematogaster are predators of H. halys nymphs in Asia, as well as in the Mediterranean, where known native predators are still few. At the same time, ants usually do not harm H. halys eggs, which are the target of the main biological control agents, the scelionid parasitoids of the genus Trissolcus. However, ants, as generalist predators and territorial organisms, may kill or displace a variety of other insects, potentially interfering with parasitoids and biological control programmes. We conducted laboratory experiments to investigate the interactions between the Mediterranean ant Crematogaster scutellaris and the parasitoids T. japonicus and T. mitsukurii, evaluating the possibility that the ants could damage the parasitized eggs, attack the parasitoids during emergence or interfere with the egg‐laying behaviour of female parasitoids. Our results demonstrate that C. scutellaris is not able to damage parasitized eggs and is not aggressive towards adult parasitoids at any stage. The presence of ants can slow down the parasitization rate in T. mitsukurii females in the smallest laboratory setups; however, this has not been observed in a more natural setting. We suggest that ants may play a complementary role together with egg‐parasitoids in the control of H. halys without interfering with each other.

Chemical and biological products used in sugarcane and their effect on Trichogramma galloi

AbstractThe parasitoid Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) is an effective biocontrol agent of the sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). Its use is often recommended in integrated pest management (IPM) programs in sugarcane. However, the IPM of this crop also involves the use of chemical and biological insecticides, and little is known about the effects of concomitant use of these products together with T. galloi. In this study, we evaluated the effects of the chemical insecticide chlorantraniliprole (Altacor 350 WG) and the biological agents Beauveria bassiana (Bals.‐Criv.) Vuill. (Granada WP), Metarhizium anisopliae (Metchnikoff) Sorokin (Opala WP), and Bacillus thuringiensis Berliner var. kurstaki (Dipel WP) on the parasitism of T. galloi adult females against D. saccharalis eggs under laboratory conditions, in addition to biological parameters of the offspring. Treatments with chlorantraniliprole and B. thuringiensis reduced the parasitism rate of T. galloi females. The biological agents M. anisopliae, B. thuringiensis, and chlorantraniliprole increased offspring mortality by more than 30%. The use of B. bassiana favored adult female parasitism rates and did not cause significant offspring mortality. None of the treatments had significant effects on the emergence, longevity, and sex ratio of the offspring. Our results suggest that an insecticide based on B. bassiana can be used concomitantly with the parasitoid T. galloi in sugarcane IPM programs. Moreover, M. anisopliae, B. thuringiensis, and chlorantraniliprole had significant undesirable effects on T. galloi; therefore, they should be used with caution to avoid potential suppression of the parasitoid effect.

Aggregation of organically managed fields promotes aphid parasitism in cereal crops under Mediterranean conditions

ContextMaintaining a balance between semi-natural habitats and arable land is not always feasible for farmers. The promotion of biological control agents can be addressed through management at farm or field level, and/or by deploying lower intensity, biodiversity-friendly practices which can act either directly or indirectly through their effect of the plant community.ObjectivesWe studied the effects on cereal aphids and their parasitoids of agricultural management at field and landscape levels. We tested the effect of organic and conventional farming, and of the within field characteristics, on the cereal aphid-parasitoid community, across a gradient of organic farming aggregation and of percentage of arable land.MethodsIn spring 2015, we sampled aphid populations in 30 cereal fields in five agricultural areas in Catalonia (Spain) with contrasting levels of organic farming aggregation. In each field, we also assessed weed and crop cover. As landscape variables, we calculated the Percentage of Agricultural Land (PAL) and the Percentage of Organically Managed Land (POML) in a 500-m buffer around each field. We sampled cereal tillers 3 m from the field edges and collected all aphids detected. In addition, we reared mummies (parasitized aphids) until they hatched.ResultsOur results show that management at landscape level has significant effects on parasitism rates: a higher proportion of surrounding fields under organic management increased the amount of parasitism, as did less agricultural land cover. On the other hand, aphid populations were mainly affected by two in-field factors, namely, crop density and crop variety. Differences in weed communities did not seem to have any effects on either aphids or parasitoids.ConclusionsRather than concentrating on the individual management of fields, a coordinated implementation of organic farming at landscape level would seem to be a much better strategy for improving the biological control of aphids.

Preference study of Trichogramma pintoi (Voegele) (Hymenoptera:Trichogrammatidae) on host eggs of different ages and species

Eggs of Ephestia kuehniella (Zeller), Cadra cautella (Walker) and Plodia interpunctella (Hübner) are host of parasitoid Trichogramma pintoi (Hymenoptera: Trichogrammatidae) which is used in biological control of pests. In this study, the host species and egg age preferences were determined in the parasitization performance of the adult female of T. pinto. For host species and egg age preference, 1, 2, 3 and 4 days old eggs from three different hosts were given to the parasitoid which were kept in controlled conditions until they hatched and then counted. Adult T. pintoi species were also stored at 4±1 °C up to 4 days. It was determined that the fecundity and life span of female parasitoids decreased as the storage period increased. T. pintoi was found to prefer up to 1 day eggs old in all three hosts. Parasitoid preferred 2, 3, and 4 days old eggs of all host species at the similar rates. Eggs of E. kuehniella and C. cautella were determined as the most preferred host, followed by eggs of P. interpunctella. Adult T. pintoi females stored for 1 day were found as the most surviving female individuals. The highest parasitization rate was also determined in females stored for 1 day. Host species, egg age preference and storage time of adult parasitoid are thought to be very important in mass production and release studies of T. pintoi.

Olfaction Response and Fertility Life Table Parameters of Tetrastichus howardi (Hymenoptera: Eulophidae) Parasitizing Plutella xylostella (Lepidoptera: Plutellidae) and the factitious host Tenebrio molitor (Coleoptera: Tenebrionidae).

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes the diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), but not much is known about its potential as a biocontrol agent. A rearing protocol has been established for this parasitoid on pupae of the factitious host Tenebrio molitor (L.) (Coleoptera: Tenebrionidae), with the aim of releasing it in the field to manage several lepidopteran species. The potential population growth of a parasitoid can be measured through fertility life tables and provide supporting information for using T. howardi in the management of P. xylostella. Also, the fitness and behavior of T. howardi reared on a factitious host can be indicators of its potential to control P. xylostella. Thus, in this study, the fertility life table parameters of T. howardi parasitizing P. xylostella were determined, as well as the effects of the natal host on the behavior of T. howardi towards host volatiles and parasitism rate. The results showed that net reproduction rate (Ro) and the intrinsic rate of population growth (rm) of T. howardi parasitizing P. xylostella were 13.6 (♀/♀) and 0.124 (♀/♀*day), respectively, whereas the mean generation time was 20.9days. Moreover, the natal host (T. molitor or P. xylostella) did not affect the fitness, parasitism rate, or olfactory response of T. howardi. In general, regardless of the natal host, parasitoid females responded to volatiles of both host species and exhibited the same rate of parasitism on P. xylostella. Therefore, T. howardi reared on the factitious host maintains its attraction and potential to parasitize P. xylostella, and can contribute to the biological control of this pest.

Role of parasitoids and landscape structure in aphid population dynamics in winter canola

Three aphid species infest winter canola, Brassica napus L. fields in central Oklahoma and are serious pests: the cabbage aphid, Brevicoryne brassicae L., green peach aphid, Myzus persicae (Sulzer), and turnip aphid, Lipaphis pseudobrassicae (Davis). Mortality caused by parasitoids may be an important component of biological control of aphids in Oklahoma canola fields. Therefore, it is important to determine the effect of parasitoids on aphids in canola and the factors that affect it. We undertook a study during three consecutive growing seasons to: 1) estimate aphid suppression by parasitoids in each of 23 canola fields using cages that excluded natural enemies and cages that permitted access by parasitoids; and 2) evaluate how aphid parasitism in canola is related to the composition and configuration of the landscape surrounding each canola field. Parasitism was estimated using turnip aphid infested sentinel canola plants stationed in each field in autumn and in spring of each growing season. Two parasitoids with broad host ranges, Diaeretiella rapae (M’Intosh) and Aphelinus nigritus (Howard), parasitized turnip aphids in canola. There were fewer aphids and more parasitoids in cages that permitted access to parasitoids than in cages that excluded natural enemies. Partial redundancy analysis demonstrated that parasitism rate by D. rapae was positively related to landcover of wetlands and negatively related to contagion of patches. Parasitism by A. nigritus was positively but weakly associated with landcover of summer crops, but not with any other measured landscape variable. Wetlands in central Oklahoma agricultural landscapes apparently are habitat for aphid parasitoids from which they disperse to canola fields and parasitize aphids. Partial redundancy analysis showed that relative aphid density in fields was negatively related to parasitism by D. rapae. Results indicate that parasitoids suppress aphid infestations in canola fields and demonstrate potential for habitat management to improve biological control of aphids in canola.

The lepidopteran pest complex infesting menthol mint in India: Distribution during the crop development, species composition and associated parasitoids

Menthol mint, Mentha arvensis L. is an important aromatic and medicinal herb cultivated as an industrial crop for its essential oil in the Indo-Gangetic plains of India. The commercial production of menthol mint suffers due to defoliation caused by lepidopteran pests and currently becoming a serious constraint for its clean cultivation. The information on occurrence of lepidopteran caterpillars defoliating menthol mint in the region is limited. In this study, we assessed the occurrence and injury caused by lepidopteran pests from seven major menthol mint growing districts of the Indo-Gangetic plains of India. Further, the species composition of lepidopteran pests and their associated parasitoids were also reported. The survey revealed that seven lepidopteran pest infestations were recorded on different phenological growth stages of menthol mint in the Indo-Gangetic plains of India. The larval population density of lepidopteran pests was significantly different between the districts, species and phenological stages of menthol mint. The larval population density of the lepidopteran pest varied between 0.41 ± 0.31 to 2.37 ± 1.43 larvae/m2 across the locations. The higher occurrence of Spodoptera litura (Fabricius), Spilarctia obliqua Walker and Thysanoplusia orichalcea (Fabricius) was recorded in menthol mint. The higher incidence of lepidopteran pests was recorded at the mid-vegetative growth stage of menthol mint. This study found eight parasitoids parasitizing egg and larval stages of lepidopteran pests. The parasitism rate of egg parasitoids, Trichogramma chilonis Ishii and Trichogramma achaeae Nagaraja and Nagarkatti was 23.53–35.31% and 27.78% to the eggs of Helicoverpa armigera and T. orichalcea, respectively. The larval parasitoids caused a total of 5.78% larval parasitism to the various lepidopteran pests of menthol mints. This information provides a current pest status of lepidopteran pests infesting menthol mint in Indo-Gangetic plains of India. This baseline information could be used for the development of management strategies against lepidopteran pests for sustainable menthol mint production.

Augmentative biological control for squash bug (Hemiptera: Coreidae) using the egg parasitoid, Hadronotus pennsylvanicus (Hymenoptera: Scelionidae).

The squash bug, Anasa tristis (De Geer) (Hemiptera: Coreidae), is a serious pest of cucurbit crops across the United States. Conventional growers commonly use broad-spectrum insecticides to manage squash bugs, however organic growers lack these effective chemical tools and must rely on alternative management strategies. Biological control of A. tristis is largely understudied, specifically the potential of natural enemy, Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae), as an augmentative biological control agent. For this reason, we performed early-season field releases of H. pennsylvanicus on organic farms in southeastern Virginia to test if this would improve A. tristis egg parasitism. We chose organic vegetable farms growing summer squash (Cucurbita pepo L.) as release sites and nearby Virginia Tech Agricultural Research Extension Centers (AREC) as no-release sites. Parasitoids were reared in the lab and deployed as parasitized egg masses (~2-3 females wasps/plant) in June 2020 and 2021. Before parasitoid deployment, host eggs collected from release and no-release sites displayed low levels of H. pennsylvanicus parasitism in 2020 (<21%) and 2021 (<8%). In both years, the percentage of A. tristis eggs parasitized within 2 weeks post deployment was significantly greater at release sites (~60%) than at no-release sites (~14%). High rates of H. pennsylvanicus parasitism (>72%) were further observed at release sites 4, 6, 8, and 10 weeks following parasitoid deployment. Our study demonstrates that releases of lab-reared H. pennsylvanicus can increase A. tristis egg parasitism rates and subsequently decrease successful nymph hatch rates in early summer squash plantings.

Parasitoids of the cabbage seed weevil deliver high and consistent parasitism in variable landscapes: A showcase of conservation biocontrol.

Insect pest resistance to insecticides and societal pressure to reduce pesticide load has increased oilseed rape (OSR) farmers' motivation to protect and exploit parasitoids for pest control. However, parasitoid presence and parasitism must be made visible to influence farmers' spraying decisions. Parasitism of cabbage seed weevil (CSW) (Ceutorhynchus obstrictus (Marsham)) reduces damage to OSR immediately, making them a good case for demonstrating conservation biocontrol to farmers. We assessed the occurrence and activity of CSW parasitoids in 84 OSR fields over 2 years and identified the impact of associated local landscape factors. Mean cabbage seed weevil infestation rates were 11% and 10% in 2020 and 2021, and parasitism rates were high in both years (75% and 74%, respectively). Temporal and spatial dynamics of OSR in the landscape surrounding the focal fields were important for both CSW and parasitoid numbers, suggesting a dilution effect for increasing OSR area since the previous year. A multimodel inference analysis showed that OSR-related factors were important predictors for both the infestation rate of CSW and the number of parasitoids. For parasitoids, protected nature areas and hedgerows were important. Parasitism rates were high and largely unaffected by landscape factors. CSW and its parasitoids respond similarly to interannual changes in the OSR resource; in addition, parasitoids benefit from uncropped areas in the surrounding landscape. The complexity of the pest and parasitoid response to landscape factors limits the prospect of designing landscapes for improved pest control by the parasitoids. Parasitoids of CSW may be present as local populations in agricultural landscapes with the potential for consistent and substantial parasitism. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ecology and host manipulation by an egg‐larva parasitoid of Chrysodeixis includens (Lepidoptera: Noctuidae)

AbstractParasitoids are among the main natural enemies of crop pests. Copidosoma truncatellum (Hymenoptera: Encyrtidae) is a parasitoid of Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae: Plusiinae), which is an important pest of soybean, bean, cotton, sunflower, tomato and potato. Copidosoma are parasitoids of lepidopteran egg‐larva, especially those of the subfamily Plusiinae. The embryonic development of the Copidosoma parasitoid begins in the lepidopteran egg, and this development extends to the beginning of the host larval stage of the parasitized lepidopteran. However, the rate of parasitism is a complex ecological relationship affected by climatic elements and age of the host. Thus, the present study aimed to investigate the ecology and host manipulation exerted by the C. truncatellum parasitoid on C. includens. The research was conducted in bean crops (Phaseolus vulgaris) over 2 years. The highest rates of parasitism were observed in crops in March in both years, when it was observed that about 40% of the individuals of C. includens were parasitized by C. truncatellum. In hot seasons and with less rainfall, parasitism is greater. The age of C. includens eggs (up to 3 days) did not affect C. truncatellum parasitism. The parasitized C. includens egg and caterpillar stages, which had their durations extended, showed the parasitized C. includens caterpillars presented higher leaf consumption. Additionally, this study was conducted in the field, which makes its results representative of natural conditions. Therefore, in warm and dry seasons, more significant parasitism of C. includens by C. truncatellum is expected. Parasitism increases the duration of the stages of lepidopterans and increases food consumption by its larvae.

Evaluation on Impact of Extrafloral Nectar of Kenaf, Hibiscus cannabinus L. (Malvaceae) on the Efficiency of Aenasius arizonensis (Girault) (Hymenoptera: Encyrtidae)

Extrafloral nectar (EFN) is one of the important and sustainable food source on plants which plays major role on the structuring of arthropod communities and efficiency of natural enemies. Thus it is well known for protecting plants with indirect defence mechanism against herbivores. The present Study was conducted to observe the effect of EFN on life history parameters and parasitism of Aenasius arizonensis in the Department of Entomology, Faculty of Agriculture, Annamalai University. Longevity of A. arizonensis was found highest in female and male as 32.60 and 23.70 days when fed with EFN respectively which was followed by 100% honey and glucose. Among the treatments EFN and 100% honey the number of female, male progenies produced per female were ranged from (highest to lowest) 57.00, 19.40 to 5.00, 1.00 and 30.00, 17.50 to 1.40, 1.00 respectively during five weeks. Provision of EFN and 100% honey to mated female produced 39.90 and 20.39 eggs during five weeks respectively. Sex ratio (female) of A. arizonensis was recorded highest as 83.33 in EFN at 5th week and 63.16 in 100% honey at 2nd week. Parasitization of A. arizonensis on Phenacoccus solenopsis was found highest as 79.42 for EFN and 45.24 for 100% honey during third and second week respectively. Thus, providing EFN can boost parasitoid survival, fecundity, sex ratio (female) and parasitism rates.

Successful establishment, spread, and impact of the introduced parasitoid Spathius galinae (Hymenoptera: Braconidae) on emerald ash borer (Coleoptera: Buprestidae) populations in postinvasion forests in Michigan.

Spathius galinae is a larval parasitoid native to the Russian Far East that was approved for release in the United States in 2015 for biological control of the emerald ash borer (EAB), Agrilus planipennis, an invasive beetle from Asia responsible for widespread mortality of ash trees (Fraxinus spp.) in North America. From 2015 to 2017, 1,340-1,445 females of S. galinae along with males were released into each release plot, paired with a nonrelease control plot (1-12.5 km apart), at 6 postinvasion forested sites containing abundant pole-sized ash trees in Michigan. By 2018, S. galinae had spread to all but one control plot. Based on the first year that S. galinae was found in trees in each control plot and the distances of those trees to the parasitoid release point within each site, we estimated that S. galinae spread at 3.7 (±1.9) km per year after its initial releases in 2015. The proportion of sampled trees with S. galinae broods, brood densities within sampled trees, and parasitism of EAB larvae increased sharply in both control and release plots after the last field releases in 2017, with the highest parasitism rates (42.8-60.3%) in 2020. Life table analysis showed that S. galinae alone reduced EAB's net population growth rate by 35-55% across sites from 2018 to 2020. These results demonstrate that S. galinae has established an increasing population in Michigan and now plays a significant role in reducing EAB populations in the area.