Diversity Of Parasitoid Species Research Articles

Parasitoid species diversity has no effect on protective symbiont diversity in experimental host-parasitoid populations.

How does diversity in nature come about? One factor contributing to this diversity are species interactions; diversity on one trophic level can shape diversity on lower or higher trophic levels. For example, parasite diversity enhances host immune diversity. Insect protective symbionts mediate host resistance and are, therefore, also engaged in reciprocal selection with their host's parasites. Here, we applied experimental evolution in a well-known symbiont-aphid-parasitoid system to study whether parasitoid diversity contributes to maintaining symbiont genetic diversity. We used caged populations of black bean aphids (Aphis fabae), containing uninfected individuals and individuals infected with different strains of the bacterial endosymbiont Hamiltonella defensa, which protects aphids against parasitoids. Over multiple generations, these populations were exposed to three different species of parasitoid wasps (Aphidius colemani, Binodoxys acalephae or Lysiphlebus fabarum), simultaneous or sequential mixtures of these species or no wasps. Surprisingly, we observed little selection for H. defensa in most treatments, even when it clearly provided protection against a fatal parasitoid infection. This seemed to be caused by high induced costs of resistance: aphids surviving parasitoid attacks suffered an extreme reduction in fitness. In marked contrast to previous studies looking at the effect of different genotypes of a single parasitoid species, we found little evidence for a diversifying effect of multiple parasitoid species on symbiont diversity in hosts.

A method for sampling parasitized Drosophila suzukii (Diptera: Drosophilidae) puparia from soil.

Methods to measure the diversity and biological control impact of parasitoids for the control of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) are being developed in support of biological control programs around the world. Existing methods to determine parasitism levels and parasitoid species composition focus on sampling D. suzukii within fresh and rotting fruit. However, many D. suzukii pupate in the soil or in dropped fruit, where additional parasitism could occur and where their parasitoids are thought to overwinter. Here we introduce a method for extracting parasitized D. suzukii puparia from the soil through a sieve and flotation system, allowing for effective collection of puparia, from which parasitoids can then be reared. Although the method considerably underestimates the absolute number of puparia in soil samples, it nonetheless yields a high number of puparia relative to sampling effort and provides a robust estimate of the relative abundance of puparia among samples. Using this method, we confirmed that at least 5 species of parasitoids, including some that have rarely been detected in past studies, overwinter in their immature stages inside D. suzukii puparia in south coastal British Columbia, Canada. The ability to sample puparia from the soil will lead to a more comprehensive view of both D. suzukii and parasitoid abundance throughout the season, help confirm parasitoid establishment following intentional releases, and provide a way to measure the diversity of parasitoid species and potential interactions among parasitoids (e.g., hyper- or klepto-parasitism) that may often occur on the soil surface.

Parazytoidy z podrodzin Pimplinae (Hymenoptera, Ichneumonidae)i Aphidiinae (Hymenoptera, Braconidae) występujące w zieleni miejskiej miasta Poznania

The study aimed to determine the species composition and abundance of parasitoids from the subfamilies Pimplinae (Hymenoptera, Ichneumonidae) and Aphidiinae (Hymenoptera, Braconidae) found in various habitats in urban greenery and to demonstrate the rela¬tionship between plant species diversity and the species structure of parasitoid assemblages. It was found that only for the subfamily Aphidiinae was there a significant effect of habitats on the abundance of individual assemblages and the effect of years on the total abundance of assemblages. A positive relationship was observed between vegetation diversity and the abundance and species diversity of parasitoids of the subfamily Aphidiinae, as well as similarity in the qualitative-quantitative structure of Pimplinae assemblages present in a given habitat. Positive effects of trees: Betula pendula, Tilia tomentosa, Salix alba and Salix caprea, shrubs: Berberis julianae, Ber¬beris vulgaris and Spiraea japonica, and herbaceous plants: Elymus repens, Festuca rubra and Hypochoeris radicata on the qualitative¬-quantitative structure of parasitoid assemblages of the subfamily Pimplinae by creating a suitable food base for these entomophagous imagines were noted.

Natural parasitism of the coffee leaf miner: climate factors, insecticide, and landscape affecting parasitoid diversity and their ecosystem services in coffee agroecosystems.

Climate factors, pesticides, and landscape in coffee agroecosystems directly affect the populations of the coffee leaf miner and its parasitoids. This study aimed to investigate the effects of climate factors, insecticide use, and landscape on natural parasitism, parasitoid diversity, and infestation of L. coffeella in coffee plantations in the Planalto region, Bahia, Brazil. Mined leaves were collected monthly in six coffee plantations with varying edge density, vegetation cover, landscape diversity in scales of 500 to 3000 m of radius, insecticide use, and climate factors. Closterocerus coffeellae, and Proacrias coffeae (Eulophidae) predominated in the pest's natural parasitism. Our record is the first for the occurrence of Stiropius reticulatus, Neochrysocharis sp. 1, Neochrysocharis sp. 2, and Zagrammosoma sp. in Bahia. Higher temperature and larger forest cover increased the coffee leaf miner infestation. Higher rainfall values, insecticide use, and landscape diversity decreased the pest infestations. Natural parasitism and species diversity are favoured by increase in temperature, forest cover, and edge density, while increase in rainfall, insecticide use, and landscape diversity lead them to decrease.The natural parasitism and diversity of parasitoid species of the coffee leaf miner have been enhancing in the areas with greater forest cover and edge density associated with low use of insecticides. The areas composed of different lands with annual croplands surrounding the coffee plantations showed less natural parasitism and parasitoid species diversity. The ecosystem services provided by C. coffeellae and P. coffeae in coffee crops areas require conservation and these species are potential bioproducts for applied biological control programmes.

Moderate Grazing Promotes Arthropod Species Diversity in an Alpine Meadow.

Livestock grazing is an important tool used in grassland land management practices. Studies have substantially addressed the effect of grazing on plant species diversity, revealing that moderate grazing increases plant species diversity. However, few studies have dealt with the relationship between grazing and arthropod species diversity, which remains unclear. Here, we hypothesize that moderate grazing promotes arthropod species diversity because arthropods are directly or indirectly dependent on plant diversity. In this study, we conducted a two-year plant and arthropod survey from 2020 to 2021 at four levels of grazing intensity, i.e., nongrazing (as a control), light grazing, moderate grazing, and heavy grazing, of the long-term grazing experiment starting in 2016. The data show that plant species diversity peaked in the moderate grazing treatment, and herbivore species diversity was positively correlated with plant species diversity (and hence peaked in the moderate grazing treatment). Moderate grazing promoted parasitoid species diversity, which was positively correlated with herbivore species diversity. However, predator species diversity did not significantly differ among the four treatments. In addition, saprophage species diversity decreased, whereas coprophages increased with increasing grazing levels, such that species richness (but not species diversity of detritivores statistically) was highest in the moderate grazing treatment. Consequently, the species diversity of arthropods as a whole peaked at the moderate grazing level, a phenomenology that is consistent with the intermediate disturbance hypothesis. Considering that moderate grazing has been found to increase plant species diversity, facilitate soil carbon accumulation, and prevent soil erosion, we suggest that moderate grazing would maximize multi-functional ecosystem services.

Comparative effects of biopesticides on fall armyworm management and larval parasitism rates in northern Ghana

The outbreak of the fall armyworm, Spodoptera frugiperda, in Africa has led to several recommendations of insecticides, including biopesticides. However, the effects of these products on the environment, especially on parasitoids have not been assessed under field conditions. Here, we investigated the effect of commonly used biopesticides on S. frugiperda management and larval parasitoids of S. frugiperda in northern Ghana. The experiments were conducted both on-station in Wa and Nyankpala and on-farm in Wa during the 2020 rainy season. Active ingredients tested included neem oil (3% Azadirachtin), maltodextrin (282 g/l), 55% Bacillus thuringiensis (Bt) combined with 45% Monosultap, and a Pieris rapae granulosis virus combined with 5% Bt. A chemical insecticide based on emamectin benzoate and acetamiprid was used as positive control while non-treated maize plots were considered as untreated control. The two most abundant parasitoids in Wa were Coccygidium luteum and Chelonus bifoveolatus, while in Nyankpala they were C. luteum and Meteorus sp. Total larval parasitism rates on-station were 18.7% and 17.6% in Wa and Nyankpala, respectively, and 8.8% in Wa on-farm. Parasitoid species diversity and evenness indexes did not vary among treatments, but parasitism rates were significantly lower with the chemical on-station in Wa and with the virus and Bt product in Nyankpala. Untreated maize plots showed the highest larval density and plant damage, the highest cob damage, and generated the lowest yields. The other treatments showed hardly any difference in cob damage and yields, suggesting that biopesticides should be preferred over chemical pesticides for S. frugiperda control.

Natural parasitism in fruit fly (Diptera: Tephritidae) and interaction with wild hosts surrounding apple orchards adjacent to Atlantic Forest fragments in Paraná State, Brazil.

The South American fruit fly, Anastrepha fraterculus (Wiedemann, 1830) (Diptera: Tephritidae), is an important pest in the subtropical region of Brazil. This insect has tritrophic relation between wild fruits and parasitoids and is associated with apple (Malus domestica Borkh.) orchards adjacent to the Atlantic Forest in Paraná. We thus investigated the degree of infestation of the fruit fly and natural parasitism in wild and cultivated fruits surrounding apple orchards. For this purpose, we collected fruits of Acca sellowiana (Berg.) Burret, Campomanesia xanthocarpa (Mart), Eugenia uniflora L., Eugenia pyriformis Cambessèdes, Psidium cattleianum Sabine, Psidium guajava (L.), Annona neosericea Rainer and Eriobotrya japonica (Thumb) in apple orchards adjacent to the Atlantic Forest located in Campo do Tenente, Lapa and Porto Amazonas counties. In total, we collected 18,289 fruits during four growing years. The occurrence of A. fraterculus depends on the susceptible period of apple fruits. A. sellowiana and P. cattleianum were considered primary fruit fly multipliers and P. guajava was secondary, all occurring after the apple harvest (IS period). The group of parasitoids with A. fraterculus was Aganaspis pelleranoi (Brèthes, 1924) (Hymenoptera: Figitidae), Opius bellus (Gahan, 1930), Doryctobracon areolatus (Szépligeti, 1911) and Doryctobracon brasiliensis (Szépligeti, 1911) (Hymenoptera: Braconidae) all of which are first records in the Atlantic Forest in Paraná. First record of O. bellus occurring in the State of Paraná, as well as, first record of the tritrophic association between host plant A. neosericea, parasitoids D. areolatus and O. bellus and fruit fly A. fraterculus. The host P. cattleianum stood out among the Myrtaceae species in regard to the high diversity of parasitoid species (81% of parasitoids). The total number of Figitidae species (76.5%) was higher than that of Braconidae species. The influence of climatic events in southern Brazil on wild fruit production should be further studied to understand the association of A. fraterculus with the tritrophic relationship.

Abundance, not diversity, of host beetle communities determines abundance and diversity of parasitoids in deadwood.

Most parasites and parasitoids are adapted to overcome defense mechanisms of their specific hosts and hence colonize a narrow range of host species. Accordingly, an increase in host functional or phylogenetic dissimilarity is expected to increase the species diversity of parasitoids. However, the local diversity of parasitoids may be driven by the accessibility and detectability of hosts, both increasing with increasing host abundance. Yet, the relative importance of these two mechanisms remains unclear. We parallelly reared communities of saproxylic beetle as potential hosts and associated parasitoid Hymenoptera from experimentally felled trees. The dissimilarity of beetle communities was inferred from distances in seven functional traits and from their evolutionary ancestry. We tested the effect of host abundance, species richness, functional, and phylogenetic dissimilarities on the abundance, species richness, and Shannon diversity of parasitoids. Our results showed an increase of abundance, species richness, and Shannon diversity of parasitoids with increasing beetle abundance. Additionally, abundance of parasitoids increased with increasing species richness of beetles. However, functional and phylogenetic dissimilarity showed no effect on the diversity of parasitoids. Our results suggest that the local diversity of parasitoids, of ephemeral and hidden resources like saproxylic beetles, is highest when resources are abundant and thereby detectable and accessible. Hence, in some cases, resources do not need to be diverse to promote parasitoid diversity.

Diversity of Hymenoptera parasitoid in organic and conventional arabica coffee plantations in Aceh Tengah District, Aceh Province, Indonesia

This research is a descriptive exploratory study. The purpose of this study was to determine the diversity of parasitoids in coffee plantations that are managed organically and conventionally. Based on statistical analysis shows that the composition and diversity of the Hymenoptera parasitoid in Arabica coffee plantations in Aceh Tengah District is influenced by cultivation techniques (organic and conventional). Both the number of families and species of Hymenoptera parasitoid found in organic coffee plantations were higher than those found in conventional ones. In organic coffee plantations, 8 families and 15 species were found, while in conventional plantations there were only 4 families and 10 species. The parasitoid species diversity index value (H') in organic coffee plantations was better than conventional coffee plantations, while the evenness index value (E) on organic and conventional coffee plantations was relatively more likely (not statistically different) and to be classified as good categories. This indicates that there are several families of the Hymenoptera parasitoid that dominate both in organic and in conventional coffee plantations. The low diversity of the Hymenoptera parasitoid in conventional coffee plantations is thought to be a result of the continued application of synthetic pesticides, thus affecting the extinction of various parasitoid species.

Seasonal abundance of Plutella xylostella (Lepidoptera: Plutellidae) and diversity of its parasitoids along altitudinal gradients of the eastern Afromontane

Monthly field surveys of diamondback moth (DBM), Plutella xylostella (L.) and its parasitoids were conducted to assess seasonal abundance and diversity under changing altitude. Twenty-four crucifer farms spread across three altitudinal zones of Mount Kilimanjaro and Taita hills were sampled for the insects at monthly interval from 2013 to 2014. Diamondback moth abundance differed significantly between seasons (F3, 21 = 3.883, p = 0.024) in the high zone of Taita hills. The abundance among altitudinal zones of the two transects was not significantly different (Mt. Kilimanjaro: F2, 98 = 0.415, p = 0.661; Taita hills: F2, 116 = 0.303, p = 0.739). Eight parasitoid species emerged in the laboratory from collected DBM larvae and pupae. Cotesia vestalis (Haliday) provided the most DBM parasitism in the low zone and Diadegma semiclausum (Hellen) in the medium and high zones. Parasitism by D. semiclausum increased by 32.5% between the low and medium zones (p = 0.001) of Taita hills. Diversity of parasitoid species declined considerably from the low to medium zones of Taita hills. The diversity of wild crucifer species increased with altitude but was twice as diverse in the high zone of Mt. Kilimanjaro than the high zone of Taita hills. Ecological complexity of the cropping system contributed greatly to a wider parasitoid diversity along Mt. Kilimanjaro. The introduced C. vestalis has successfully established in East Africa and adapted to the warmer areas in the low altitudes.

Exploration for native parasitoids of Drosophila suzukii in China reveals a diversity of parasitoid species and narrow host range of the dominant parasitoid

Drosophila suzukii is native to East Asia and an invasive pest of fruit crops widely established in the Americas and Europe. The lack of effective indigenous parasitoids of D. suzukii in the invaded regions prompted surveys for co-evolved parasitoids in Yunnan Province, China, from 2013 to 2016. From banana-baited traps (2013–2015), 458 parasitoids of drosophilids were reared, comprised of Braconidae (49.56%), Figitidae (37.55%), Diapriidae (7.42%), and Pteromalidae (5.46%). Larval parasitoids included seven braconid species, all Asobara and primarily Asobara mesocauda, and five figitid species, primarily Leptopilina japonica japonica. Pupal parasitoids were the diapriid Trichopria drosophilae and the pteromalid Pachycrepoideus vindemiae. Collections from wild fruits (2016) provided more interesting results. From the puparia of drosophilids collected, comprised of D. suzukii and Drosophila pulchrella, emerged 1354 parasitoids. The larval parasitoids Ganaspis brasiliensis and L. j. japonica were the prevalent species, reaching a fairly high percentage parasitism of fly puparia collected from berries of Rubus foliosus (22.35%), R. niveus (18.81%), Fragaria moupinensis (19.75%), and Sambucus adnata (63.46%). Ganaspis brasiliensis was the dominant species and was collected only from D. suzukii and D. pulchrella-infested fruits and never from banana-baited traps. Molecular analysis showed two G. brasiliensis lineages, which are discussed with respect to previous Japanese collections. Quarantine tests showed that G. brasiliensis developed from D. suzukii and two closely related hosts (Drosophila melanogaster and Drosophila simulans) but did not develop from seven non-target drosophilid species. Our results suggest that G. brasiliensis is a promising classical biocontrol agent for release in invaded regions.

KELIMPAHAN DAN KEANEKARAGAMAN PARASITOID PADA PERTANAMAN MENTIMUN (Cucumis sativus)

Abundance and diversity of parasitoids is strongly associated with the presence of pests and vegetation around cucumber plantings. This study aims to determine the abundance and diversity of parasitoid species in cucumber plantings. The research was conducted at four cucumber planting locations in Bogor, West Java. Insect sampling is done using yellow pan traps and malaise traps. The results show the highest species abundance obtained at the Cibatok of 632 individuals and the lowest in Cibanteng 197 individuals. The highest Shannon-Wiener index value at Cangkurawuk is 4.2927 and the evenness of species is 0.92. The high abundance of individuals is not always accompanied by the higher value of diversity and evenness too. Keywords: abundance, cucumber, diversity, parasitoid

A two-year study of parasitoid entomofauna associated with spruce bark beetles (Coleoptera: Curculionidae) in the altimontane belt of Slovenia (Pohorje)

Parasitoids are known to be an important factor in the population density regulation of bark beetles. In our study of the parasitoid complex of spruce bark beetles in 2011 and 2012, we collected bark samples from trees infested with I. typographus from spruce stands in the altimontane belt of Slovenia. The samples were taken at different altitudes: 450, 700 and 1230 m above sea level. A total of 9 bark beetle species and 12 parasitoid species was found. Ips typographus was most abundant, with 93% of all species of scolytids. The parasitoid species that were found belonged mainly to the Pteromalidae and Braconidae families. By far the most abundant and frequent species was Roptrocerus xylophagorum, which represented 84% of all parasitoids and was present in all study samples. Differences in species composition, parasitoid species diversity, species abundance and parasitism rate were confirmed between locations and also between both years of our study.

Histories of host shifts and cospeciation among free-living parasitoids of Rhagoletis flies.

Host shifts by specialist insects can lead to reproductive isolation between insect populations that use different hosts, promoting diversification. When both a phytophagous insect and its ancestrally associated parasitoid shift to the same novel host plant, they may cospeciate. However, because adult parasitoids are free living, they can also colonize novel host insects and diversify independent of their ancestral host insect. Although shifts of parasitoids to new insect hosts have been documented in ecological time, the long-term importance of such shifts to parasitoid diversity has not been evaluated. We used a genus of flies with a history of speciation via host shifting (Rhagoletis [Diptera: Tephritidae]) and three associated hymenopteran parasitoid genera (Diachasma, Coptera and Utetes) to examine cophylogenetic relationships between parasitoids and their host insects. We inferred phylogenies of Rhagoletis, Diachasma, Coptera and Utetes and used distance-based cophylogenetic methods (ParaFit and PACo) to assess congruence between fly and parasitoid trees. We used an event-based method with a free-living parasitoid cost model to reconstruct cophylogenetic histories of each parasitoid genus and Rhagoletis. We found that the current species diversity and host-parasitoid associations between the Rhagoletis flies and parasitoids are the primary result of ancient cospeciation events. Parasitoid shifts to ancestrally unrelated hosts primarily occur near the branch tips, suggesting that host shifts contribute to recent parasitoid species diversity but that these lineages may not persist over longer time periods. Our analyses also stress the importance of biologically informed cost models when investigating the coevolutionary histories of hosts and free-living parasitoids.

TINGKAT PARASITASI PARASITOID TELUR PBPK PADA PERTANAMAN PADI DENGAN BEBERAPA KETINGGIAN TEMPAT BERBEDA

Rice is the staple food of Indonesia's population. Various problems occur in an effort to increase production and productivity. One problem is the attack of yellow rice stem borer (PBPK) which may result in yield losses up to 90%. Utilization of parasitoid is an alternative to suppress the attack of Yellow Rice Stem Borer. The study was conducted in Tabanan, covering three locations with the altitudes of 50, 300, and 550 meters above sea leve, and at the Plant Pests and Diseases laboratory of the Faculty of Agriculture, University of Udayana. The study aimed to determine the effectiveness of parasitization of the best Yellow Rice Stem Borer as a natural control agent at different altitudes. The method used was survey by taking a sample group of Yellow Rice Stem Borer eggs with a purposive random sampling in the area of 2.5 hectares (one block in each location was an area of 0.5 hectares) at each location. Observations on parasitoid found in Yellow Rice Stem Borer eggs were done on parasitoid species diversity, equality, abundance, parasitation level, sex ratio, and the pattern of parasitoid invasion. The results showed three species of parasitoid eggs PBPK as biological control agents. Parasitation level of T. rowani and T. japonicum was the highest at the altitude of 50 meters above sea level, while T. schoenobii at the altitude of 300 and 500 meters above sea level.

Diversity of Stink Bug (Hemiptera: Pentatomidae) Egg Parasitoids in Woodland and Crop Habitats in Southwest Georgia, USA

Euschistus servus (Say), Chinavia hilaris (Say), and Nezara viridula (L.) (Hemiptera: Pentatomidae) are economic pests of row crops. They move within and between closely associated crop and non-crop habitats throughout the growing season in response to deteriorating suitability of their current host plants. This study was conducted to investigate parasitism of naturally occurring C. hilaris and E. servus eggs in woodland habitats and crops alongside these habitats in southwest Georgia, USA. Also, parasitism of sentinel eggs of N. viridula was examined in a woodland habitat. Ten species of parasitoids, including 7 scelionids, 2 eupelmids, and 1 encyrtid, parasitized E. servus eggs. Telenomus podisi Ashmead (Hymenoptera: Scelionidae) was the most prevalent parasitoid of E. servus eggs in each of 3 habitats: woodlands, an early-season crop, and late-season crops. In woodlands, 27.9% of E. servus eggs were parasitized by Anastatus reduvii (Howard) and A. mirabilis (Walsh & Riley) (Hymenoptera: Eupelmidae). Four species of parasitoids, including 1 scelionid, 2 eupelmids, and 1 encyrtid, parasitized C. hilaris eggs. Trissolcus edessae Fouts (Hymenoptera: Scelionidae) was the most prevalent parasitoid of C. hilaris eggs in woodlands and the only parasitoid of C. hilaris eggs in late-season crops. In woodlands, 40.7% of C. hilaris eggs were parasitized by A. reduvii and A. mirabilis. In a woodland habitat, 6.6% of N. viridula sentinel eggs were parasitized by A. reduvii females, Anastatus males, and 1 encyrtid. Anastatus species were the only parasitoids that existed primarily in woodland habitats. In conclusion, a diversity of parasitoid species parasitizes native stink bug eggs in southwest Georgia, and species of parasitoids emerging from stink bug eggs can vary by habitat.

Species composition and diversity of parasitoids and hyper-parasitoids in different wheat agro-farming systems.

Insect communities depend on both their local environment and features of the surrounding habitats. Diverse plant communities may enhance the abundance and species diversity of local natural enemies, which is possible due to a higher abundance and species diversity in complex landscapes. This hypothesis was tested using cereal aphid parasitoids and hyper-parasitoids by comparing 18 spring wheat fields, Triticum aestivum L. (Poales: Poaceae), in structurally-complex landscapes (dominated by semi-natural habitat, > 50%, n = 9) and structurally-simple landscapes dominated by arable landscape (dominated by crop land, > 80%, n = 9). The agricultural landscape structure had significant effects on the number of parasitoid and hyper-parasitoid species, as 26 species (17 parasitoids and 9 hyper-parasitoids) were found in the complex landscapes and 21 were found in the simple landscapes (14 parasitoids and 7 hyper-parasitoids). Twenty-one species occurred in both landscape types, including 14 parasitoids and 7 hyper-parasitoids species. The species diversity of parasitoids and hyper-parasitoids were significantly different between the complex and simple landscapes. In addition, arable fields in structurally-simple agricultural landscapes with little semi-natural habitats could support a lower diversity of cereal aphid parasitoids and hyper-parasitoids than structurally-complex landscapes. These findings suggest that cereal aphid parasitoids and hyper-parasitoids need to find necessary resources in structurally-complex landscapes, and generalizations are made concerning the relationship between landscape composition and biodiversity in agricultural landscapes. Overall, abundance, species richness, and species diversity increased with increasing plant diversity and landscape complexity in spring wheat fields and increasing amounts of semi-natural habitats in the surrounding landscape.

Studies on the Parasitoids of the Serpentine Leaf Miner, Liriomyza trifolii (Burgess) in Tomato Ecosystem under Mid Hill Condition of Himachal Pradesh

The species diversity of parasitoids of the serpentine leaf miner, Liriomyza trifolii (Burgess) in tomato ecosystem was conducted under mid hill conditions of Himachal Pradesh during 2008–2010. The tomato leaves were collected periodically from June to September from three strata i.e. bottom, middle and top portion of the plants at random. During the course of study four species of larval parasitoids viz., Neochrysocharis formosa (Westwood), Diglyphus sp., Asecodes sp. and Chrysocharis sp. belonging to the family Eulophidae and one species of larval-pupal parasitoid, Opius sp. belonging to the family Braconidae were identified. These parasitoids were active throughout the cropping season and the parasitization ranged from 6.0 - 21.1, 19.4 - 28.6 and 13.6 - 23.1 per cent during 2008, 2009 and 2010, respectively. It was maximum (20.1 - 28.6%) during the month of August. Marginally higher parasitization (14.3 - 26.7%) was observed in the middle stratum of the foliage than in top (11.1 - 24.0%) or bottom (6.7 - 20.0%) stratum during all the three years of study. Among the larval parasitoids, N. formosa was the predominant species (81.5%), whereas, other parasitoids such as Diglyphus sp., Chrysocharis sp. and Asecodes sp. comprised of 7.4, 7.4 and 3.7 per cent of the total population of the larval parasitoids.

Edges in Agricultural Landscapes: Species Interactions and Movement of Natural Enemies

Agricultural landscapes can be characterized as a mosaic of habitat patches interspersed with hostile matrix, or as a gradient of patches ranging from suitable to unsuitable for different species. Arthropods moving through these landscapes encounter a range of edges, with different permeability. Patches of native vegetation in these landscapes may support natural enemies of crop pests by providing alternate hosts for parasitic wasps and/or acting as a source for predatory insects. We test this by quantifying species interactions and measuring movement across different edge-types. A high diversity of parasitoid species used hosts in the native vegetation patches, however we recorded few instances of the same parasitoid species using hosts in both the native vegetation and the crop (canola). However, we did find overall greater densities of parasitoids moving from native vegetation into the crop. Of the parasitoid groups examined, parasitoids of aphids (Braconidae: Aphidiinae) frequently moved from native vegetation into canola. In contrast, parasitoids of caterpillars (Braconidae: Microgastrinae) moved commonly from cereal fields into canola. Late season samples showed both aphids and parasitoids moving frequently out of native vegetation, in contrast predators moved less commonly from native vegetation (across the whole season). The season-long net advantage or disadvantage of native vegetation for pest control services is therefore difficult to evaluate. It appears that the different edge-types alter movement patterns of natural enemies more so than herbivorous pest species, and this may impact pest control services.

Recolonisation of an apple orchard by leafrollers (Lepidoptera: Tortricidae) following spraying

The recolonisation of a 2.2 ha apple block by three leafroller species was studied in autumn in each of 2 years, 1–4 months after an intensive organophosphate insecticide programme finished. Two transects at right angles, each bisecting the block, were set up with 16 stations located 0–40 m in from each side and one in the centre. Between 60 and 80% of larvae, shoot damage, pheromone and molasses bait trap catches were recorded within 10 m of the outermost trees. The presence of leafroller-hosting trees adjacent to the orchard had a major influence on the spatial pattern of infestation. Adult leafrollers were trapped throughout the study, but few larvae and little shoot damage appeared until 3–4 months after spraying stopped. Ctenopseustis obliquana (51%) and Planotortrix octo (44%) comprised the majority of larvae. Compared with these proportions, catches in bait and pheromone traps under-represented C. obliquana, but over-represented Epiphyas postvittana. Almost 4 months after spraying ended, the parasitism rate (3%) and parasitoid species diversity had not recovered to levels at sites where organophosphates were not used. The implications of these results for current integrated fruit production practices are discussed.