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Barbara Wagener - One of the best experts on this subject based on the ideXlab platform.
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Molecular systematics of selected Diadegma species (Hymenoptera: Ichneumonidae: Campoplegine) important in biological control
2007Co-Authors: Barbara WagenerAbstract:The genus Diadegma (Hymenoptera: Ichneumonidae: Campopleginae) represents a large group of parasitoids with 201 species worldwide. Adult Diadegma females parasitise larvae of various lepidopteran species and some species, in particular Diadegma insulare (Cresson) and D. semiclausum (Hellen), have gained economic importance as biological control agents of Plutella xylostella (Linnaeus). A low parasitism rate of
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molecular systematics of selected Diadegma species hymenoptera ichneumonidae campoplegine important in biological control
2007Co-Authors: Barbara WagenerAbstract:The genus Diadegma (Hymenoptera: Ichneumonidae: Campopleginae) represents a large group of parasitoids with 201 species worldwide. Adult Diadegma females parasitise larvae of various lepidopteran species and some species, in particular Diadegma insulare (Cresson) and D. semiclausum (Hellen), have gained economic importance as biological control agents of Plutella xylostella (Linnaeus). A low parasitism rate of <15 % of the parasitoid complex (Diadegma sp., Oomyces sokolowskii (Kurdjumov) and Diaplazon laetatorius (Fabricius)) in unsprayed cabbage and kale fields infested with P. xylostella in eastern and southern Africa was the starting point for the development of a biological control project for P. xylostella which was implemented by the International Centre of Insect Physiology and Ecology (ICIPE), Kenya. One of the objectives of the biocontrol project was to examine the taxonomic status of Diadegma species associated with P. xylostella in eastern and southern Africa and the exotic parasitoid D. semiclausum imported to Kenya from Taiwan (Asian Vegetable Research and Development Centre, AVRDC) by cross breeding experiments and molecular methods. Thus, two different molecular regions, a fragment of the mitochondrial cytochrome c oxidase subunit (COI) and the second internal transcribed spacer (ITS2) of ribosomal DNA were amplified utilising polymerase chain reaction (PCR) and digested afterwards with several restriction enzymes (PCR-Restriction Fragment Length Polymorphism-RFLP). In the due course of the study examinations of several Diadegma species attacking P. xylostella were undertaken with the PCR-RFLP method developed previously for the African Diadegma. This molecular method could solve some taxonomic difficulties of the genus Diadegma. Sequence analyses were used to investigate the phylogenetic relationship of nine Diadegma species (D. blackburni (Cameron), D. insulare, D. leontiniae (Brethes), D. chrysostictos (Gmelin), D. armillata (Gravenhorst), D. fenestrale (Holmgren), D. mollipla (Holmgren), D. semiclausum, D. rapi (Cameron)) and the phylogenetic relationship of the genus Diadegma within the superfamily Ichneumonoidea. Cross breeding experiments were carried out between two populations of D. mollipla from eastern and southern Africa. No significant differences in the total number of progeny per female and the number of male offspring were obtained, whereas the female progeny showed significant differences. Hybrid females resulting from both reciprocal crosses were reproductively compatible with males of both parental lines, which indicated that no genetic incompatibility was apparent between the two D. mollipla populations. In contrast, crosses between D. mollipla and D. semiclausum resulted only in the occurrence of male offspring, which is typical for unfertilised progeny in Diadegma. The laboratory cultures of D. mollipla and D. semiclausum were highly male biased. Inbreeding, where homozygosity is much higher, is leading to a higher diploid male production. Diploid males can easily be detected by isoenzyme variations as a genetic marker. Heterozygote females/males of D. semiclausum and D. mollipla were identified by phosphoglucomutase (PGM) electrophoretic banding patterns. Crosses between a mother (heterozygote, diploid) and her son (homozygote, haploid) resulted in one diploid male in D. mollipla and none in D. semiclausum. Information about diploid males in D. semiclausum detected with PGM has already been published and different methodologies might be the reason why in D. semiclausum no diploid male was detected. Therefore the present analyses with PGM as molecular marker should be seen as a preliminary study. Die Gattung Diadegma (Hymenoptera: Ichneumonidae: Campopleginae) umfasst eine grosse Gruppe von Schlupfwespen mit 201 Arten weltweit. Das Wirtsspektrum beschrankt sich auf die Ordnung Lepidoptera, wo sie die Larven- und Puppenstadien parasitieren. Diadegma insulare (Cresson) and D. semiclausum (Hellen) haben okonomische Bedeutung und werden zur biologischer Bekampfung der Kohlmotte (Plutella xylostella (Linnaeus) erfolgreich eingesezt. Im ostlichen und sudlichen Afrika wurde 1998 herausgefunden, dass in unbehandelten, von P. xylostella befallenen Kohlfeldern, die Parasitierungsleistung eines Komplexes bestehend aus Diadegma sp., Oomyces sokolowskii (Kurdjumov) und Diaplazon laetatorius (Fabricius) bei der Kohlmotte unter 15 % lag. Diese Erkenntnis fuhrte zu der Entwicklung eines Projektes zur biologischen Bekampfung der Kohlmotte im ostlichen Afrika, welches seit 2000 vom International Centre of Insect Physiology and Ecology (ICIPE),Kenia, durchgefuhrt wird. Im Rahmen dieses Projektes entstand die vorliegende Arbeit, wobei in erster Linie der taxonomische Status der Diadegma Arten aus dem ostlichen und sudlichen Afrika sowie des aus Taiwan (Asian Vegetable Research and Development Centre, AVRDC) nach Kenia eingefuhrten Parasitoiden D. semiclausum mit Versuchen zur genetischen Vertraglichkeit (Kreuzungsversuche) und mit molekularbiologischen Methoden untersucht werden sollte. Dabei wurden mit Hilfe der Polymerasekettenreaktion (PCR) zwei sich unterschiedlich entwickelnde genetische Regionen (ein Fragment der mitochonrialen Cytochrome c Oxidase Untereinheit (COI) sowie der zweite ?internal spacer? (ITS2) der ribosomalen DNA) amplifiziert und anschliessend mit Restriktionsenyzmen verdaut (PCR-Restriction Fragment Length Polymorphism-RFLP). Desweiteren wurden mit Hilfe von Sequenzierungen die phylogenetischen Beziehungen zwischen neun Diadegma Arten (D. blackburni (Cameron), D. insulare, D. leontiniae (Brethes), D. chrysostictos (Gmelin), D. armillata (Gravenhorst), D. fenestrale (Holmgren), D. mollipla (Holmgren), D. semiclausum, D. rapi (Cameron)) sowie die Beziehung der Gattung Diagema innerhalb der Uberfamilie Ichneumonoidea aufgezeigt. In Kreuzungsversuchen zwischen der sudafrikanischen D. mollipla Population und der kenianischen D. mollipla Population sowie zwischen Ruckkreuzungen wurden keine signifikanten Unterschiede zwischen den Nachkommen pro Weibchen und der mannlichen Nachkommenschaft festgestellt. Signifikante Unterschiede bestanden jedoch im Auftreten der weiblichen Nachkommen. Hybride weibliche Nachkommen aus beiden reziproken Kreuzungen waren reproduktiv mit Mannchen aus beiden elterlichen Populationen, was darauf zuruckzufuhren ist, dass keine genetische Unvertraglichkeit zwischen den beiden raumlich getrennten D. mollipla Populationen besteht. Dagegen war eine Kreuzung zwischen D. mollipla und D. semiclausum nicht moglich; sie fuhrte nur zu Mannchen. Dies ist typisch fur eine unbefruchtete Nachkommenschaft bei Diadegma. Die Laborkulturen von D. mollipla und D. semiclausum waren durch Inzucht gekennzeichnet, was durch den hohen Anteil von Mannchen sichtbar wurde. Inzucht fuhrt zu einer hoheren Homozygotie und dadurch zu einem starkeren Auftreten von diploiden Mannchen. Diese konnen leicht mit Hilfe von Isoenzym-Variationen identifiziert werden. Heterozygote Weibchen/ Mannchen von D. semiclausum und D. mollipla wurden mit Phosphoglukomutase (PGM) elektrophoretisch aufgetrennt. Bei Kreuzungen zwischen Mutter (heterozygot, diploid) and ihrem Sohn (homozygot, haploid) wurde ein diploides Mannchen in D. mollipla und keines in D. semiclausum gefunden. Aufgrund der geringen Anzahl von Tieren und der kurzen Versuchsdauer sollten die vorliegenden Versuche jedoch als Vorstudien gewertet werden.
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phylogenetic study of Diadegma species hymenoptera ichneumonidae inferred from analysis of mitochondrial and nuclear dna sequences
Biological Control, 2006Co-Authors: Barbara Wagener, B Lohr, Annette Reineke, C P W ZebitzAbstract:Abstract The genus Diadegma consists of a large group of parasitoid wasps with a confusing taxonomy based on morphological characters. No phylogenetic studies on this genus or any of its species have been published so far. We examined DNA variations in a 498 bp segment of the cytochrome oxidase I gene (COI) of mitochondrial DNA (mtDNA) and in the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA) and compared nine different Diadegma species (i.e., D. semiclausum, D. insulare, D. fenestrale, D. mollipla, D. rapi., D. leontiniae, D. chrysostictos, D. armillata, D. blackburni) from various geographical origins. Interspecific variation ranged from 3.9 to 16.8% in the COI region and from 5.4 to 32.5% in the ITS2. Phylogenetic relationships were constructed on maximum parsimony and maximum likelihood trees for each marker. Likelihood ratio tests were used to find the best evolutionary model fitting each of the data sets. The cladistic analysis of both data sets yielded different tree topologies. The sequences of the COI gene provided very little resolution of relationships among species whereas the nuclear DNA sequence data (ITS2 region) seems to be phylogenetically more valuable.
B Lohr - One of the best experts on this subject based on the ideXlab platform.
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can low release numbers lead to establishment and spread of an exotic parasitoid the case of the diamondback moth parasitoid Diadegma semiclausum hellen in east africa
Crop Protection, 2008Co-Authors: G Gichini, B Lohr, A Rossbach, B Nyambo, R GathuAbstract:Abstract From 2001 onwards, Diadegma semiclausum, an exotic parasitoid of the diamondback moth, was introduced and released in Kenya, Tanzania and Uganda. Contrary to common practice where thousands of parasitoids are released, we released very low numbers, 125 females in Kenya, 160 in Uganda and 350 in Tanzania. About 2 years after this single release, the establishment and natural spread of the parasitoids was assessed in all release areas. Two methods were employed: in Kenya, a grid with equidistant points in the four cardinal directions (2–50 km) with the release area in the centre was used and collections were made 27 months after release at the predetermined points. The parasitoid was found up to a distance of 30 km from the release site. In Tanzania and Uganda, surveys were made starting from the release area following major roads. At regular intervals, fields were inspected and their position recorded with a Geographic Positioning System (GPS). The results of a field survey conducted 24 months after release indicate that in Tanzania, the parasitoid had spread >20 km from the release site while in Uganda, the spread was >30 km. Wherever D. semiclausum was collected, it was the major parasitoid species. Indigenous parasitoids collected were Oomyzus sokolowskii (Hym.: Eulophidae), Diadegma mollipla (Hym.: Ichneumonidae) and Apanteles sp. (Hym.: Braconidae). Overall parasitism and the contribution of the introduced parasitoid to the control of diamondback moth population tended to decrease with increasing distance from the release point. The introduced parasitoid had displaced the indigenous species wherever it was well established.
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interspecific competition between Diadegma semiclausum hellen and Diadegma mollipla holmgren parasitoids of the diamondback moth plutella xylostella l feeding on a new host plant
Bulletin of Entomological Research, 2008Co-Authors: A Rossbach, B Lohr, Stefan VidalAbstract:Interspecific competition between an introduced parasitoid species aimed at controlling a herbivorous pest species and a native parasitoid parasitising the same host may influence the success of classical biological control programmes. In Kenya, interspecific competition between an introduced and a local parasitoid on two diamondback moth populations (DBM, Plutella xylostella ) was investigated on two different host plants. We tested simultaneous and delayed competition of the local parasitoid Diadegma mollipla Holmgren and its exotic congenus D. semiclausum Hellen on a newly aquired DBM host plant (snowpea) in the laboratory. Under simultaneous competition, D. mollipla produced more progeny than D. semiclausum on snowpea. A head start of D. Mollipla , of four and eight hours before its congenus was introduced, resulted in a similar number of progeny of both species. In delayed competition (time intervals of 24 h, 48 h and 72 h), progeny production was similar for both parasitoids when the time interval was 24 h, irrespective of which species parasitized first. More progeny was produced by the species which attacked first, when the time interval was greater than 24 h, although it was only significant at 72 h. Competitive abilites of both parasitoids on the new host plant differed largely between laboratory and semi-field conditions. The influence of two host plants (snowpea and cabbage) on competition was studied in the greenhouse with different host and parasitoid densities. Parasitism levels of D. semiclausum were significantly higher than those of D. mollipla , regardless of host plant, host and parasitoid densities, but progeny production of D. mollipla on snowpea was still slightly higher than on cabbage. As compared to the confinement of parasitoids and larvae to small containers, D. mollipla parasitized very few larvae in the cages. Competitive ability of the two parasitoid species tested was influenced both by the density of the searching females and by parameters related to either the host plant and/or the herbivorous hosts.
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host shift to peas in the diamondback moth plutella xylostella lepidoptera plutellidae and response of its parasitoid Diadegma mollipla hymenoptera ichneumonidae
Bulletin of Entomological Research, 2006Co-Authors: A Rossbach, B Lohr, Stefan VidalAbstract:Host shifts in herbivorous insects are thought to sometimes provide enemy-free space on the novel host plant. A population of the diamondback moth Plutella xylostella (Linnaeus), an oligophagous pest on crucifers, recently shifted to sugar snap- and snowpeas ( Pisum sativum ) in Kenya, resulting in heavy damage to these crops. The impact of this host shift on the interaction with Diadegma mollipla (Holmgren), one of the most frequent parasitoid species attacking P. xylostella in this area, was investigated. Parasitism rates and development of two strains of D. mollipla , one reared from a cabbage-feeding strain of P. xylostella and the second from the new pea-feeding strain, changed based on the host-plant that P. xylostella fed upon, with both parasitoid strains more effective on the novel host plant. Parasitism by the cabbage- D. mollipla strain on P. xylostella infesting peas was four times higher than on P. xylostella infesting cabbage when a single plant species was present. However, when both crops were offered together, the level of parasitism dropped to the level seen when cabbage was offered alone. Diadegma mollipla developed on both hosts, but cabbage- D. mollipla had a longer total development time. Pupae of cabbage-feeding P. xylostella were significantly heavier than pupae of pea-feeding P. xylostella and parasitism had no influence on these differences. Diadegma mollipla preferred to parasitize the pea-feeding P. xylostella . Thus, the host shift by P. xylostella to a novel host plant did not necessarily provide enemy-free space, with the parasitoid species tested. The implications of these findings for the host–parasitoid relationship are discussed.
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phylogenetic study of Diadegma species hymenoptera ichneumonidae inferred from analysis of mitochondrial and nuclear dna sequences
Biological Control, 2006Co-Authors: Barbara Wagener, B Lohr, Annette Reineke, C P W ZebitzAbstract:Abstract The genus Diadegma consists of a large group of parasitoid wasps with a confusing taxonomy based on morphological characters. No phylogenetic studies on this genus or any of its species have been published so far. We examined DNA variations in a 498 bp segment of the cytochrome oxidase I gene (COI) of mitochondrial DNA (mtDNA) and in the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA) and compared nine different Diadegma species (i.e., D. semiclausum, D. insulare, D. fenestrale, D. mollipla, D. rapi., D. leontiniae, D. chrysostictos, D. armillata, D. blackburni) from various geographical origins. Interspecific variation ranged from 3.9 to 16.8% in the COI region and from 5.4 to 32.5% in the ITS2. Phylogenetic relationships were constructed on maximum parsimony and maximum likelihood trees for each marker. Likelihood ratio tests were used to find the best evolutionary model fitting each of the data sets. The cladistic analysis of both data sets yielded different tree topologies. The sequences of the COI gene provided very little resolution of relationships among species whereas the nuclear DNA sequence data (ITS2 region) seems to be phylogenetically more valuable.
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Generalism Versus Specialism: Responses of Diadegma mollipla (Holmgren) and Diadegma semiclausum (Hellen), to the Host Shift of the Diamondback Moth (Plutella xylostella L.) to Peas
Journal of Insect Behavior, 2005Co-Authors: A Rossbach, B Lohr, S. VidalAbstract:A population of the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) (DBM) was recently found to infest sugar snap- and snowpeas in the Rift Valley in Kenya, causing heavy damage. The influence of this host shift on host location preferences of two parasitoids was investigated: The indigenous Diadegma mollipla (Holmgren) regarded as a relative generalist, and Diadegma semiclausum (Hellen), regarded as highly specific to DBM. The attractiveness of different odour sources was compared for the two parasitoid species using a Y-tube olfactometer using naïve females. D. mollipla was not significantly attracted to any cabbage related odours but showed a significant preference for the DBM infested pea plant when tested against clean air. D. semiclausum was highly attracted to the undamaged cabbage plant and odours related to cabbage. On the other hand, peas infested with DBM, showed no attractiveness to this parasitoid. The results showed that specialisation of D. semiclausum is mediated by host plant signals, associated with crucifers, which are not encountered in DBM feeding on peas. For D. mollipla ,although a frequent parasitoid on DBM in crucifers, volatiles emitted by these plants might not be used as primary cues for host location. This species may respond largely to chemicals yet unknown and associated with a variety of plant-herbivore interactions.
C P W Zebitz - One of the best experts on this subject based on the ideXlab platform.
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phylogenetic study of Diadegma species hymenoptera ichneumonidae inferred from analysis of mitochondrial and nuclear dna sequences
Biological Control, 2006Co-Authors: Barbara Wagener, B Lohr, Annette Reineke, C P W ZebitzAbstract:Abstract The genus Diadegma consists of a large group of parasitoid wasps with a confusing taxonomy based on morphological characters. No phylogenetic studies on this genus or any of its species have been published so far. We examined DNA variations in a 498 bp segment of the cytochrome oxidase I gene (COI) of mitochondrial DNA (mtDNA) and in the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA) and compared nine different Diadegma species (i.e., D. semiclausum, D. insulare, D. fenestrale, D. mollipla, D. rapi., D. leontiniae, D. chrysostictos, D. armillata, D. blackburni) from various geographical origins. Interspecific variation ranged from 3.9 to 16.8% in the COI region and from 5.4 to 32.5% in the ITS2. Phylogenetic relationships were constructed on maximum parsimony and maximum likelihood trees for each marker. Likelihood ratio tests were used to find the best evolutionary model fitting each of the data sets. The cladistic analysis of both data sets yielded different tree topologies. The sequences of the COI gene provided very little resolution of relationships among species whereas the nuclear DNA sequence data (ITS2 region) seems to be phylogenetically more valuable.
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a pcr based approach to distinguish important Diadegma species hymenoptera ichneumonidae associated with diamondback moth plutella xylostella lepidoptera plutellidae
Bulletin of Entomological Research, 2004Co-Authors: B Wagener, B Lohr, Annette Reineke, C P W ZebitzAbstract:: The diamondback moth, Plutella xylostella (Linnaeus) has a cosmopolitan distribution and is one of the major pests on cruciferous plants. Biological control, especially with species of the genus Diadegma, has been successfully employed in several parts of the world, mainly in South East Asia. The taxonomy of this genus based on classical morphological characters is still unclear and misidentifications are reported. In the present study seven Diadegma species associated with P. xylostella were separated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses. The second internal transcribed spacer (ITS2) of the ribosomal DNA (rDNA) was successfully amplified in all 167 individuals and digested using 11 different restriction enzymes. One restriction enzyme (CfoI) showed different restriction profiles in all species and also between two population samples of D. mollipla (Holmgren) from eastern and southern Africa. In addition, a new Diadegma species associated with P. xylostella from Ethiopia was discovered.
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molecular identification of Diadegma species ichneumonidae parasitising diamondback moth plutella xylostella plutellidae in eastern and southern africa
Improving biocontrol of #Plutella xylostella# : Proceedings of the International Symposium Montpellier France 21-24 October 2002, 2004Co-Authors: B Wagener, B Lohr, Annette Reineke, C P W ZebitzAbstract:Sequencing of the second internal transcribed spacer (ITS2) of the ribosomal DNA followed by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis were used to differentiate Diadegma species (Ichneumonidae) parasitising Diamond back moth DBM in eastern and southern Africa. The maximum nucleotide divergence between D. mollipla and D. semiclausum was 6.8%, whereas D. sp. from Ethiopia differs in - 35%, The intraspecific divergence was 0.3% in Diadegma mollipla, and 0.7% in Diadegma semiclausum. (Resume d'auteur)
A Rossbach - One of the best experts on this subject based on the ideXlab platform.
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can low release numbers lead to establishment and spread of an exotic parasitoid the case of the diamondback moth parasitoid Diadegma semiclausum hellen in east africa
Crop Protection, 2008Co-Authors: G Gichini, B Lohr, A Rossbach, B Nyambo, R GathuAbstract:Abstract From 2001 onwards, Diadegma semiclausum, an exotic parasitoid of the diamondback moth, was introduced and released in Kenya, Tanzania and Uganda. Contrary to common practice where thousands of parasitoids are released, we released very low numbers, 125 females in Kenya, 160 in Uganda and 350 in Tanzania. About 2 years after this single release, the establishment and natural spread of the parasitoids was assessed in all release areas. Two methods were employed: in Kenya, a grid with equidistant points in the four cardinal directions (2–50 km) with the release area in the centre was used and collections were made 27 months after release at the predetermined points. The parasitoid was found up to a distance of 30 km from the release site. In Tanzania and Uganda, surveys were made starting from the release area following major roads. At regular intervals, fields were inspected and their position recorded with a Geographic Positioning System (GPS). The results of a field survey conducted 24 months after release indicate that in Tanzania, the parasitoid had spread >20 km from the release site while in Uganda, the spread was >30 km. Wherever D. semiclausum was collected, it was the major parasitoid species. Indigenous parasitoids collected were Oomyzus sokolowskii (Hym.: Eulophidae), Diadegma mollipla (Hym.: Ichneumonidae) and Apanteles sp. (Hym.: Braconidae). Overall parasitism and the contribution of the introduced parasitoid to the control of diamondback moth population tended to decrease with increasing distance from the release point. The introduced parasitoid had displaced the indigenous species wherever it was well established.
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interspecific competition between Diadegma semiclausum hellen and Diadegma mollipla holmgren parasitoids of the diamondback moth plutella xylostella l feeding on a new host plant
Bulletin of Entomological Research, 2008Co-Authors: A Rossbach, B Lohr, Stefan VidalAbstract:Interspecific competition between an introduced parasitoid species aimed at controlling a herbivorous pest species and a native parasitoid parasitising the same host may influence the success of classical biological control programmes. In Kenya, interspecific competition between an introduced and a local parasitoid on two diamondback moth populations (DBM, Plutella xylostella ) was investigated on two different host plants. We tested simultaneous and delayed competition of the local parasitoid Diadegma mollipla Holmgren and its exotic congenus D. semiclausum Hellen on a newly aquired DBM host plant (snowpea) in the laboratory. Under simultaneous competition, D. mollipla produced more progeny than D. semiclausum on snowpea. A head start of D. Mollipla , of four and eight hours before its congenus was introduced, resulted in a similar number of progeny of both species. In delayed competition (time intervals of 24 h, 48 h and 72 h), progeny production was similar for both parasitoids when the time interval was 24 h, irrespective of which species parasitized first. More progeny was produced by the species which attacked first, when the time interval was greater than 24 h, although it was only significant at 72 h. Competitive abilites of both parasitoids on the new host plant differed largely between laboratory and semi-field conditions. The influence of two host plants (snowpea and cabbage) on competition was studied in the greenhouse with different host and parasitoid densities. Parasitism levels of D. semiclausum were significantly higher than those of D. mollipla , regardless of host plant, host and parasitoid densities, but progeny production of D. mollipla on snowpea was still slightly higher than on cabbage. As compared to the confinement of parasitoids and larvae to small containers, D. mollipla parasitized very few larvae in the cages. Competitive ability of the two parasitoid species tested was influenced both by the density of the searching females and by parameters related to either the host plant and/or the herbivorous hosts.
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host shift to peas in the diamondback moth plutella xylostella lepidoptera plutellidae and response of its parasitoid Diadegma mollipla hymenoptera ichneumonidae
Bulletin of Entomological Research, 2006Co-Authors: A Rossbach, B Lohr, Stefan VidalAbstract:Host shifts in herbivorous insects are thought to sometimes provide enemy-free space on the novel host plant. A population of the diamondback moth Plutella xylostella (Linnaeus), an oligophagous pest on crucifers, recently shifted to sugar snap- and snowpeas ( Pisum sativum ) in Kenya, resulting in heavy damage to these crops. The impact of this host shift on the interaction with Diadegma mollipla (Holmgren), one of the most frequent parasitoid species attacking P. xylostella in this area, was investigated. Parasitism rates and development of two strains of D. mollipla , one reared from a cabbage-feeding strain of P. xylostella and the second from the new pea-feeding strain, changed based on the host-plant that P. xylostella fed upon, with both parasitoid strains more effective on the novel host plant. Parasitism by the cabbage- D. mollipla strain on P. xylostella infesting peas was four times higher than on P. xylostella infesting cabbage when a single plant species was present. However, when both crops were offered together, the level of parasitism dropped to the level seen when cabbage was offered alone. Diadegma mollipla developed on both hosts, but cabbage- D. mollipla had a longer total development time. Pupae of cabbage-feeding P. xylostella were significantly heavier than pupae of pea-feeding P. xylostella and parasitism had no influence on these differences. Diadegma mollipla preferred to parasitize the pea-feeding P. xylostella . Thus, the host shift by P. xylostella to a novel host plant did not necessarily provide enemy-free space, with the parasitoid species tested. The implications of these findings for the host–parasitoid relationship are discussed.
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Generalism Versus Specialism: Responses of Diadegma mollipla (Holmgren) and Diadegma semiclausum (Hellen), to the Host Shift of the Diamondback Moth (Plutella xylostella L.) to Peas
Journal of Insect Behavior, 2005Co-Authors: A Rossbach, B Lohr, S. VidalAbstract:A population of the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) (DBM) was recently found to infest sugar snap- and snowpeas in the Rift Valley in Kenya, causing heavy damage. The influence of this host shift on host location preferences of two parasitoids was investigated: The indigenous Diadegma mollipla (Holmgren) regarded as a relative generalist, and Diadegma semiclausum (Hellen), regarded as highly specific to DBM. The attractiveness of different odour sources was compared for the two parasitoid species using a Y-tube olfactometer using naïve females. D. mollipla was not significantly attracted to any cabbage related odours but showed a significant preference for the DBM infested pea plant when tested against clean air. D. semiclausum was highly attracted to the undamaged cabbage plant and odours related to cabbage. On the other hand, peas infested with DBM, showed no attractiveness to this parasitoid. The results showed that specialisation of D. semiclausum is mediated by host plant signals, associated with crucifers, which are not encountered in DBM feeding on peas. For D. mollipla ,although a frequent parasitoid on DBM in crucifers, volatiles emitted by these plants might not be used as primary cues for host location. This species may respond largely to chemicals yet unknown and associated with a variety of plant-herbivore interactions.
Oliver Balmer - One of the best experts on this subject based on the ideXlab platform.
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spread and global population structure of the diamondback moth plutella xylostella lepidoptera plutellidae and its larval parasitoids Diadegma semiclausum and Diadegma fenestrale hymenoptera ichneumonidae based on mtdna
Bulletin of Entomological Research, 2017Co-Authors: I Juric, Walter Salzburger, Oliver BalmerAbstract:The diamondback moth (DBM) (Plutella xylostella) is one of the main pests of brassicaceous crops worldwide and shows resistance against a wide range of synthetic insecticides incurring millions of dollars in control costs every year. The DBM is a prime example of the introduction of an exotic species as a consequence of globalization. In this study we analyzed the genetic population structure of the DBM and two of its parasitic wasps, Diadegma semiclausum and Diadegma fenestrale, based on mitochondrial DNA sequences. We analyzed DBM samples from 13 regions worldwide (n = 278), and samples of the two wasp species from six European and African countries (n = 131), in an attempt to reconstruct the geographic origin and phylogeography of the DBM and its two parasitic wasps. We found high variability in COI sequences in the diamondback moth. Haplotype analysis showed three distinct genetic clusters, one of which could represent a cryptic species. Mismatch analysis confirmed the hypothesized recent spread of diamondback moths in North America, Australia and New Zealand. The highest genetic variability was found in African DBM samples. Our data corroborate prior claims of Africa as the most probable origin of the species but cannot preclude Asia as an alternative. No genetic variability was found in the two Diadegma species. The lack of variability in both wasp species suggests a very recent spread of bottlenecked populations, possibly facilitated by their use as biocontrol agents. Our data thus also contain no signals of host-parasitoid co-evolution.
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Molecular markers for Diadegma (Hymenoptera: Ichneumonidae) species distinction and their use to study the effects of companion plants on biocontrol of the diamondback moth
BioControl, 2015Co-Authors: Ivan Juric, Walter Salzburger, Henryk Luka, Oliver BalmerAbstract:Molecular markers facilitate the quantification of parasitization of pest species and the distinction of related parasitoid species. We designed new markers that allow the distinction of often misidentified Diadegma semiclausum and D. fenestrale parasitization in field-collected diamondback moth ( Plutella xylostella ) larvae. The markers were applied to study if cornflower ( Centaurea cyanus ) companion plants increase parasitization of the diamondback moth by Diadegma parasitoids in cabbage fields, as they do in the Mamestra brassicae — Microplitis mediator pest-parasitoid pair. Among 1708 P. xylostella larvae analyzed, we found a high parasitization rate (72.2 % total, 41.7 % by D. semiclausum, 24.9 % by D. fenestrale , 5.6 % by both), but no significant effects of cornflower presence. Our results highlight the need for species-specific markers and the specific action of companion plants. To increase natural control in crop fields, habitat management needs to be tailored to—and acts on—specific target species.