Native parasitoids associated with Tuta absoluta in the tomato production areas of the Spanish Mediterranean Coast

The tomato borer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an invasive pest that produces significant damage to tomato crops in the Mediterranean area. Although several species of predatory bugs are successfully being used for biological control of the pest, little is known about the parasitoids that are able to exploit T. absoluta as a host. With the aim of better understanding parasitoid species richness of T. absoluta along the Mediterranean Spanish Coast, we conducted an extensive survey to determine distribution, host plants and habitats where parasitoids are present. Our results indicated that egg parasitoids are naturally scarce but that the species richness of larval/pupal parasitoids is high and includes 20 different species. Seven of these had not been previously reported as T. absoluta parasitoids. The most frequent parasitoid species recovered were Necremnus sp. nr. artynes (Walker), Stenomesius cf. japonicus (Ashmead) and Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae).     

First field evidence that parasitoids use upwind anemotaxis for host-habitat location

The direction of flight of natural populations of Phradis interstitialis (Thomson), Tersilochus obscurator Aubert (both Hymenoptera: Ichneumonidae), and Platygaster subuliformis (Kieffer) (Hymenoptera: Platygastridae), parasitoids of three crucifer‐specialist herbivores, to and from their hosts’ host plant [oilseed rape, Brassica napus L. (Brassicaceae)] was studied in the field within a heterogeneous arable environment. Double‐sided Malaise traps encircling a plot of winter oilseed rape (cultivar Lutin) were used to sample the parasitoids as they flew towards and away from the plot during spring and summer. Daily trap catch of parasitoids and trap air flow were compared using Spearman's rank correlation. For all 14 insect days analysed, and for each species, the correlations between daily catch of parasitoids into distal halves of traps (relative to the plot) and wind direction were negative, significantly so on half the days analysed. This confirmed that flights towards the plot were by upwind anemotaxis. In contrast, the correlations between daily catch of parasitoids into proximal halves of traps (relative to the plot) and wind direction were most often crosswind; they were never strongly nor significantly either negative or positive. Implications of the results for integrated pest management strategies incorporating biological control with these parasitoids are discussed.     

How parasitoid sex ratio,size and emergence time are associated with fruit tree cultivar,within-orchard tree position and ants

The biocontrol potential of naturally occurring parasitoids is influenced by the parasitoids’ population and individual characteristics. We studied field determinants of characteristics of the parasitoid Scambus pomorum (Hymenoptera: Ichneumonidae) emerging from weevils (Anthonomus pomorum; Coleoptera: Curculionidae) hidden in damaged apple blossoms. The studied determinants comprised local-scale factors that can be managed by individual growers: tree cultivar, distance between apple trees and forest, and presence of ants. The studied parasitoid characteristics were sex ratio, body size and emergence time. Parasitoid sex ratio, in general female-biased, was significantly different for parasitoids emerging from hosts feeding on different apple cultivars. This finding suggests sex ratio adjustment driven by plant genotype-dependent variation in parasitoid host quality. The detected significant increase of sex ratio (more males) with increasing distance to forest might be explained by sperm depletion of ovipositing parasitoid females immigrating into the orchard. Exclusion of ants significantly increased female-bias in sex ratio in one of the studied apple cultivars. Body size of female and male parasitoids was significantly different between parasitoids emerging from different apple cultivars, supporting the view of cultivar-dependent variation in the quality of the parasitoid’s host. Distance to forest was positively correlated with parasitoid size, indicating farther dispersal of larger individuals. Emergence time varied significantly between apple cultivars, probably due to differences in plant phenology. By demonstrating that parasitoid characteristics vary widely within an orchard, this study shows that parasitoid characteristics that are relevant for biological control might be improved via appropriate management of the orchard and its immediate surroundings.     

Addition to the study of the genus Dusona (Hymenoptera,Ichneumonidae, Campopleginae) in Korea with description of a new species and key to the Korean species

Korean species of the genus Dusona Cameron (Hymenoptera: Ichneumonidae: Campopleginae) are reviewed. Twenty seven species of Dusona are reported from South Korea, including 12 previously unrecorded species, D. bellipes (Holmgren, 1872), D. bicoloripes (Ashmead, 1906), D. chabarowski Hinz & Horstmann, 2004, D. cultrator (Gravenhorst, 1829), D. japonica (Cameron, 1906), D. mactatoides Hinz, 1994, D. scalprata Horstmann, 2004, D. sasayamae Hinz & Horstmann, 2004, D. oblitera (Holmgren, 1872), D. obtutor Hinz, 1994, D. auriculator Aubert, 1964, D. longicauda (Uchida, 1928), and a new species, D. koreana sp. n. An illustrated key to Korean species of Dusona provided.     

Endoparasitoids of larval Anomis privata (Lepidoptera: Noctuidae), major pest of Hibiscus syriacus (Columniferae: Malvaceae)

Endoparasitoids of Anomis privata larvae include five species in three families of two orders. In this work, two species of Hymenoptera Braconidae (Cotesia sp., Microplitis sp.), one species of Ichneumonidae (Mesochorus vittator) and two species of Diptera Tachinidae (Exorista (Podotachina) sorbillans, Timavia amoena) were investigated. Of the 261 larvae of A. privata examined, 32 had a parasite, so the rate of parasitism was 12.26%. Parasitism by taxon was the highest, at 10.35% (27 individuals), in Cotesia sp. in Hymenoptera Braconidae. Parasitoids of Braconidae and Ichneumonidae were larval parasitoids. A parasitic insect of Tachinidae was a larva–pupal parasitoid. Solitary parasitoids included Microplitis sp. in Braconidae and E. sorbillans in Tachinidae. Gregarious parasitoids included Cotesia sp. in Braconidae, M. vittator in Ichneumonidae and T. amoena in Tachinidae. There was also a multiparasitoid (T. amoena) and two superparasitoids (Cotesia sp., M. vittator). A larva of A. privata sought feed even after it was parasitized every parasitoid investigated in this study, so five species of parasitoids were all koinobiont.     

Potential for classical biological control of the potato bug Closterotomus norwegicus (Hemiptera: Miridae): description, parasitism and host specificity of Peristenus closterotomae sp. n. (Hymenoptera: Braconidae)

The potato bug, Closterotomus norwegicus (Gmelin) (Hemiptera: Miridae) is an introduced pest of lucerne, white clover and lotus seed crops in New Zealand and a key pest of pistachios in California, USA. Efforts were made to identify potential biological control agents of C. norwegicus in Europe. A total of eight parasitoids, including six primary parasitoids from the genus Peristenus (Hymenoptera: Braconidae) and two hyperparasitoids from the genus Mesochorus (Hymenoptera: Ichneumonidae), were reared from C. norwegicus nymphs collected in various habitats in northern Germany. With a proportion of more than 85% of all C. norwegicus parasitoids, Peristenus closterotomae (Hymenoptera: Braconidae), a new species, was the most dominant parasitoid, whereas other parasitoid species only occurred sporadically. Peristenus closterotomae did not fit in the keys to any described species and is described as new to science. Parasitism caused by P. closterotomae was on average 24% (maximum 77%). To assess the host specificity of parasitoids associated with C. norwegicus, the parasitoid complexes of various Miridae occurring simultaneously with C. norwegicus were studied. Peristenus closterotomae was frequently reared from Calocoris affinis (Herrich-Schaeffer), and a few specimens were reared from Calocoris roseomaculatus (De Geer) and the meadow plant bug, Leptopterna dolobrata (Linnaeus) (all Hemiptera: Miridae). The remaining primary parasitoids associated with C. norwegicus were found to be dominant in hosts other than C. norwegicus. Whether nymphal parasitoids may potentially be used in a classical biological control initiative against the potato bug in countries where it is introduced and considered to be a pest is discussed.     

Predation on the woodwasp Tremex longicollis Konow (Hymenoptera: Siricidae) and its parasitoid Megarhyssa jezoensis (Matsumura) (Hymenoptera: Ichneumonidae) adults during oviposition

Adults of the woodwasp Tremex longicollis Konow (Hymenoptera: Siricidae) oviposit in the wood of dying Celtis sinensis trees using their ovipositors, and adults of the parasitoid Megarhyssa jezoensis (Matsumura) (Hymenoptera: Ichneumonidae) deposit eggs into the woodwasp larvae that live in the wood, also using their long ovipositors. Many T. longicollis ovipositors, both with and without abdominal segments, and a M. jezoensis ovipositor were found stuck in C. sinensis wood at two parks in Osaka Prefecture, central Japan. Field observations showed that ovipositing woodwasps and parasitoids were attacked by predators during the daytime, and their ovipositors were left behind in the wood. Woodwasps and their parasitoids, which have long ovipositors, may be vulnerable to predation during oviposition.     

A study on the emergence sequence of pupal parasitoids of the pine processionary moth,Thaumetopoea pityocampa

The emergence of pupal parasitoids from collected pupae of Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae) was recorded over a 2-year period. The moths and the parasitoid species Villa brunnea (Diptera: Bombylidae), Phryxe caudata (Diptera: Tachinidae), Coelichneumon rudis (Hymenoptera: Ichneumonidae) emerged sequentially. The ecological implications of such parasitism are discussed.     

Biology and Seasonal Abundance of Parasitoids of the Banded Sunflower Moth (Lepidoptera: Tortricidae) in Sunflower

Mortality, parasitization, and overwintering development through pupation of the banded sunflower moth, Cochylis hospes Walsingham, larvae and two of its endoparasitoids, Glypta prognatha Dasch and Chelonus phaloniae Mason, were followed over a 2-year period (1987 to 1989). Development of parasitoids in the field was determined for each species by examination of moth eggs and larvae during the 1989 season. Parasitoids of C. hospes, recovered from cultivated sunflower, Helianthus annuus L., from North and South Dakota and Minnesota in 1994 and 1995, parasitized 24 and 17% of larvae, respectively. Species of Hymenoptera collected included G. prognatha and Trathala sp. (Ichneumonidae), C. phaloniae and Macrocentrus ancylivorus Rohwer (Braconidae), and Perilampus robertsoni Crawford (Pteromalidae). The most abundant parasitoid was G. prognatha. In 1994 and 1995, C. phaloniae, an egg-larval parasitoid, emerged earlier but was less abundant than the later occurring larval parasitoid G. prognatha. Species of parasitoids collected from cultivated sunflower and five species of native sunflowers were similar. An additional parasitoid, Mastrus sp. (Ichneumonidae), was recovered only from the native sunflowers H. annuus and H. tuberosus L. Results from 1994 and 1995 showed that parasitization rates for the total season by the two most abundant parasitoids were similar in fields using three planting dates. These results suggest that altering planting date could be successfully used as a pest management strategy without disrupting the biological control of the banded sunflower moth. Conservation of these parasitoids in the sunflower agroecosystem is needed since they play an important role in the management of C. hospes.     

Influence of initial egg density and host size on the development of the gregarious parasitoid <Emphasis Type="Italic">Bracon hebetor</Emphasis> on three different host species

Bracon hebetor (Say) (Hymenoptera : Braconidae) is a gregarious parasitoid that attacks a variety of important lepidopterous pests of stored product and in the field. In this study the effect of host species, size and larval competition on parasitoid size, survival and development were investigated. In laboratory studies, wasp eggs at a range of densities, were placed on larvae of different weight of three Lepidoptera host species namely Adoxophyes orana (Fischer von Röslerstamm, Tortricidae), Plodia interpunctella (Hubner, Pyralidae) and, Lobesia botrana(Dennis & Schiffermueller, Tortricidae). On A. orana survival of immature parasitoids was very low at all densities and different host weights. On L. botrana survival progressively reduced as egg density increased at both host weights examined for this host. Survival on P. interpunctella was significantly affected by egg density but not by host weight. Initial egg density had a significant effect on the size of emerging adults from each rearing host. Smaller adult parasitoids emerged as egg density per larva increased. Larval host weight of P. interpunctella and A. orana had a significant effect on the size of emerging adult parasitoids mainly at the higher egg densities used in these experiments. The above results of host quality on fitness of parasitoid are discussed.     

Patterns of host use in solitary parasitoids (Hymenoptera, Ichneumonidae): field evidence from a homogeneous habitat

Teder, T., Tammaru, T. and Pedmanson, R. 1999. Patterns of host use in solitary parasitoids (Hymenoptera, Ichneumonidae): field evidence from a homogeneous habitat. - Ecography 22: 79-86.
We detected a significant inter- and intraspecific host preference on the level of individual host use in a system, in which three moth species (Lepidoptera: Noctuidae), feeding on a cattail Typha latifolia , are parasitized by three solitary parasitoid species (Hymenoptera: Ichneumonidae). The biology of the host species is similar but they exhibit remarkable inter- and intraspecific variance in body size. All the parasitoid species preferred the largest host species in this system whereas other host species were used only occasionally. We found that parasitoids which emerged from females of the preferred host species were larger than those which developed in males of the same species. Accordingly, two of the parasitoid species had a significant within-host-species preference: females of the largest moth species were used more often than males. No dependence of the preference pattern on host density was found. This pattern of host use is discussed in the light of the switching theory and the optimal host selection theory. Our results indicate that non-random host use by parasitoids may have significant effects on host populations and communities, and forms a potential selective factor against large body size in herbivorous insects. Unlike the majority of ichneumonid wasps, these three parasitoid species have no remarkable female-biased sexual size dimorphism, in accordance with the predictions of Charnov's sex allocation theory for this case, we did not observe any significant host quality dependent biases in sex allocation: there was no association between host sex and parasitoid sex, neither did parasitoid sex ratio differ between years with different host quality.     

Food web associations and effect of trophic resources and environmental factors on parasitoids expanding their host range into non‐native hosts

Trophic interactions and environmental conditions determine the structure of food webs and the host expansion of parasitoids into novel insect hosts. In this study, we investigate plant–insect–parasitoid food web interactions, specifically the effect of trophic resources and environmental factors on the presence of the parasitoids expanding their host range after the invasion of Chrysodeixis chalcites (Esper) (Lepidoptera: Noctuidae). We also consider potential candidates for biological control of this non‐native pest. A survey of larval stages of Plusiinae (Lepidoptera: Noctuidae) and their larval parasitoids was conducted in field and vegetable greenhouse crops in 2009 and 2010 in various locations of Essex and Chatham‐Kent counties in Ontario, Canada. Twenty‐one plant–host insect–host parasitoid associations were observed among Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), C. chalcites, and larval parasitoids in three trophic levels of interaction. Chrysodeixis chalcites, an old‐world species that had just arrived in the region, was the most common in our samples. The larval parasitoids Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae), Cotesia vanessae (Reinhard), Cotesia sp., Microplitis alaskensis (Ashmead), and Meteorus rubens (Nees) (all Hymenoptera: Braconidae) expanded their host range into C. chalcites changing the structure of the food web. Copidosoma floridanum (Ashmead) (Hymenoptera: Encyrtidae) was the most common parasitoid of T. ni that was not found in the invasive species. Plant species, host abundance, and agro‐ecosystem were the most common predictors for the presence of the parasitoids expanding their host range into C. chalcites. Our results indicate that C. sonorensis, C. vanessae, and C. floridanum should be evaluated for their potential use in biological control of C. chalcites and T. ni.     

The role of parasitoids in regulation of Polistes wasp population (Hymenoptera, Vespidae: Polistinae)

The study conducted in 2005–2010 analyzes the behavioral response of the parasitoids Latibulus argiolus (Rossi) (Hymenoptera, Ichneumonidae) and Elasmus schmitti Ruschka (Hymenoptera, Eulophidae) to the distribution of their host, Polistes wasps (Hymenoptera, Vespidae). Various conditions of the parasitoid-host system and conditions of regulation of the host abundance are discussed. The parasitoid females are more active in wasp colony clusters and tend to infest larger nests. If the parasitoids are abundant, infestation of host colonies starts earlier, sometimes before the worker emergence; therefore, density-dependent behavioral response of parasitoids is caused primarily by the impact of the aggregation component. Thus, the host population density factor appears to be mediated not only by the non-uniform development rates of colonies and their spatial distribution, but also by the seasonal (temporal) aspect of their development. Low density of the host population, at which the parasitoids regulate the wasp abundance, corresponds to a certain phase of the seasonal colony development, namely to the period before the emergence of workers. On the whole, we are dealing with a host-parasitoid system in which the spatial and temporal factors are closely interrelated.     

Defense strategies used by two sympatric vineyard moth pests

Natural enemies including parasitoids are the major biological cause of mortality among phytophagous insects. In response to parasitism, these insects have evolved a set of defenses to protect themselves, including behavioral, morphological, physiological and immunological barriers. According to life history theory, resources are partitioned to various functions including defense, implying trade-offs among defense mechanisms. In this study we characterized the relative investment in behavioral, physical and immunological defense systems in two sympatric species of Tortricidae (Eupoecilia ambiguella, Lobesia botrana) which are important grapevine moth pests. We also estimated the parasitism by parasitoids in natural populations of both species, to infer the relative success of the investment strategies used by each moth. We demonstrated that larvae invest differently in defense systems according to the species. Relative to L. botrana, E. ambiguella larvae invested more into morphological defenses and less into behavioral defenses, and exhibited lower basal levels of immune defense but strongly responded to immune challenge. L. botrana larvae in a natural population were more heavily parasitized by various parasitoid species than E. ambiguella, suggesting that the efficacy of defense strategies against parasitoids is not equal among species. These results have implications for understanding of regulation in communities, and in the development of biological control strategies for these two grapevine pests.     

Manipulation of parasitoid state influences host exploitation by Diadromus pulchellus Wesmael (Hymenoptera: Ichneumonidae)

In biological control programs, it should be possible to manipulate agents during host specificity trials so that they exhibit a lower host acceptance threshold. This would help to ensure that any non-target species that could be attacked in the field will also be attacked in the laboratory and flagged as potential hosts. The question is how to encourage agents to express the widest possible host range during trials. This study examined the effects of variation in parasitoid state (mating status, nutritional status, age, host experience) and the test environment (competition, arena size, presence of host-damaged leek leaves) on the degree of host exploitation by Diadromus pulchellus Wesmael (Hymenoptera: Ichneumonidae). As a first step, this study looked for changes in oviposition by the parasitoid on its normal host, the leek moth, Acrolepiopsis assectella (Zeller) (Lepidoptera: Acrolepiidae). Each of the seven factors was tested independently to assess its effect on the number of parasitoid offspring produced and host mortality. Previous host experience led to a marginal increase, while competition led to a per-capita decrease, in the degree of host exploitation. In contrast, mating status, arena size and the presence of host-damaged leek leaves had no measurable effects. Finally, parasitoid age and nutritional status had strong effects in the opposite direction to predictions, with younger and sugar-fed individuals exhibiting higher host exploitation than older and sugar-starved parasitoids, respectively. This study suggests that a sound understanding of species-specific reproductive biology and parasitoid–host interactions is likely required before oviposition-enhancing parasitoid states can confidently be identified.     

Alien dominance of the parasitoid wasp community along an elevation gradient on Hawai’i Island

Through intentional and accidental introduction, more than 100 species of alien Ichneumonidae and Braconidae (Hymenoptera) have become established in the Hawaiian Islands. The extent to which these parasitoid wasps have penetrated native wet forests was investigated over a 1,765 m elevation gradient on windward Hawai’i Island. For >1 year, malaise traps were used to continuously monitor parasitoid abundance and species richness in nine sites over three elevations. A total of 18,996 individuals from 16 subfamilies were collected. Overall, the fauna was dominated by aliens, with 44 of 58 species foreign to the Hawaiian Islands. Ichneumonidae was dominant over Braconidae in terms of both diversity and abundance, comprising 67.5% of individuals and 69.0% of species collected. Parasitoid abundance and species richness varied significantly with elevation: abundance was greater at mid and high elevations compared to low elevation while species richness increased with increasing elevation, with all three elevations differing significantly from each other. Nine species purposely introduced to control pest insects were found, but one braconid, Meteorus laphygmae, comprised 98.0% of this assemblage, or 28.3% of the entire fauna. Endemic species, primarily within the genera Spolas and Enicospilus, were collected almost exclusively at mid- and high-elevation sites, where they made up 22.1% and 36.0% of the total catch, respectively. Overall, 75.9% of species and 96.0% of individuals are inferred to parasitize Lepidoptera larvae and pupae. Our results support previous data indicating that alien parasitoids have deeply penetrated native forest habitats and may have substantial impacts on Hawaiian ecosystems.     

Lack of enemy release for an invasive leafroller in California: temporal patterns and influence of host plant origin

The enemy release hypothesis posits that the success of invasive species can be attributed to their escape from natural enemies. Invading hosts are expected to encounter an enemy assemblage consisting of fewer species, with lower representation of specialists, and to experience less mortality as a result. In this study, we examined parasitism of the Light Brown Apple Moth (LBAM), Epiphyas postvittana (Walker), in California, an exotic leafroller that is native to southeastern Australia. From 2008 to 2011 we monitored parasitoid species richness, representation of the more specialized koinobiont parasitoids, and parasitism rates of LBAM collected three times per year from four plant species of Australian origin and six plant species of non-Australian origin, at two locations in coastal California. We found the resident parasitoid assemblage of LBAM in California to have comparable levels of species richness, to have a similar representation of koinobionts versus idiobionts, and to inflict similar parasitism rates as in its native range. The two dominant parasitoids were Meteorus ictericus (Braconidae) and Enytus eureka (Ichneumonidae). Parasitoid species richness varied with season and plant origin and decreased slowly, but significantly, over the 4 year period. Parasitism rates were lowest in spring and highest on plants of Australian origin, but did not change with year. Hyperparasitism rates were higher on E. eureka (36.5 %) compared with M. ictericus and other parasitoids combined (3.3 %) and were highest on plants of Australian origin. We subsequently discuss the lack of both apparent enemy reduction and realized enemy release for LBAM in California and the unique finding that a shared plant origin enhanced the parasitism of this exotic leafroller by resident parasitoids.     

闭弯尾姬蜂与菜蛾盘绒茧蜂寄生菜蛾幼虫时的种间竞争

在室内25℃下,以菜蛾3龄初幼虫作寄主,研究了菜蛾盘绒茧蜂Cotesia plutellae和半闭弯尾姬蜂Diadegma semiclausum的种间竞争。当寄主供2种蜂同时产卵寄生时,2种蜂各自的寄生率与其单独寄生时无显著差异,合计寄生率比一种蜂单独存在时有所提高,但差异不显著。2种蜂均能产卵寄生已被另一种蜂寄生了的寄主幼虫。当寄主被2种蜂寄生的间隔时间很短（少于10 h）时,所育出的蜂绝大部分（80%以上）为绒茧蜂;当寄主先被绒茧蜂寄生,并饲养2天以上再供弯尾姬蜂寄生时,所育出的全为绒茧蜂;当寄主先被弯尾姬蜂寄生,并饲养2天以上再供绒茧蜂寄生时,寄主幼虫绝大部分不能存活,只有少部分能育出寄生蜂,且多为弯尾姬蜂。当2种蜂的幼虫存在于同一寄主体内时,2种蜂的发育均受到另一种蜂的抑制;绒茧蜂1龄幼虫具有物理攻击能力,能将弯尾姬蜂卵或幼虫致死。这些结果表明,菜蛾盘绒茧蜂与半闭弯尾姬蜂在同一寄主中发育时,前者具有明显的竞争优势。     

Distribution of 18S rDNA sites and absence of the canonical TTAGG insect telomeric repeat in parasitoid Hymenoptera

Karyotypes of six species belonging to three main clades of parasitoid Hymenoptera, the superfamilies Ichneumonoidea (Ichneumonidae: Ichneumon amphibolus), Cynipoidea (Cynipidae: Diplolepis rosae) and Chalcidoidea (Eurytomidae: Eurytoma robusta, Eu. serratulae and Eu. compressa, and Torymidae: Torymus bedeguaris) were studied using FISH with 18S rDNA and telomeric (TTAGG)_n probes. Haploid karyotypes of D. rosae, Eu. robusta and Eu. serratulae carried the only 18S rDNA hybridization signal, whereas those of I. amphibolus and Eu. compressa carried three and two rDNA clusters respectively. In addition, three rDNA sites were visualized in the aneuploid female of T. bedeguaris. The number of rDNA clusters in parasitoid Hymenoptera generally correlates to the chromosome number. Apart from the overwhelming majority of the studied species of aculeate Hymenoptera, no hybridization signals were obtained from FISH with the telomeric (TTAGG)_n probe in the examined parasitoid species. These data suggest absence of the canonical (TTAGG)_n insect telomeric motif in the Ichneumonoidea, Cynipoidea and Chalcidoidea, and perhaps in parasitoid Hymenoptera in general.     

Do laboratory studies predict parasitoid interaction outcomes in the field?

Studying competitive interactions among natural enemies is important to elucidate the success and non-target impact of candidate biological control agents. Increased regulation of new introductions requires that studies on non-target species be carried out in confined conditions. Hypotheses about potential impacts of biological control agents in the field are based on data from Petri dish or small cage experiments conducted in the laboratory. This study compared the performance of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), parasitoids Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) and Microplitis plutellae (Muesebeck) (Hymenoptera: Braconidae) in experiments conducted in small cages in the laboratory and in large cages in the field. Results showed no significant differences between laboratory and field outcomes for D. insulare alone and when D. insulare and M. plutellae were combined. For M. plutellae alone, parasitism in the laboratory cages was significantly less than in the field cages. These results demonstrate that laboratory studies may be useful to develop hypotheses on competitive interactions of candidate parasitoid biological control agents.