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    Lethal and sublethal effects of preimaginal treatments with two pyrethroids on the life history of the egg parasitoid Telenomus busseolae
    (Springer, 2010) Bayram, Ahmet; Salerno, Gianandrea; Onofri, Andrea; Conti, Eric
    The egg parasitoid Telenomus busseolae Gahan (Hymenoptera: Scelionidae) is one of the most important natural enemies of the Mediterranean corn stem borer, Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae). The effects of lethal and sublethal concentrations of two commonly used pyrethroids, deltamethrin and cyfluthrin, on emergence, fecundity, longevity, and offspring sex ratio of T. busseolae exposed during different preimaginal stages were studied. The insecticide, the tested concentrations of the insecticide (field-recommended concentration and three dilutions with twofold concentration decreases), and the stage of parasitoid preimaginal development (first and second larval stages and pupae) all significantly influenced the percentage of emergence. Life history parameters of parasitoids exposed to the highest and lowest tested concentrations of the two insecticides (3.0 and 0.375 ml l(-1) for cyfluthrin and 0.5 and 0.0625 ml l(-1) for deltamethrin) at eight days post-oviposition (pupal stage) were calculated. The intrinsic rate of increase, the total progeny produced, and the net reproductive rate of the parasitoid were all adversely affected by the field-recommended concentrations of at least one insecticide. However, the longevity, the length of the oviposition period, and the offspring sex ratio were unaltered by the two insecticides. The effects of sublethal concentrations of the insecticides, applied at preimaginal stages, on the responses of T. busseolae females to host abdominal scales, were studied in open-arena bioassays. Cyfluthrin altered both the residence time and linear speed of the parasitoid in the host scale-containing areas, whereas deltamethrin had no effect. Our results indicate that, in addition to lethal effects, sublethal effects should also be considered when evaluating insecticide consequences on non-targets.
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    Origin and taxonomic status of the Palearctic population of the stem borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae)
    (Oxford Univ Press, 2011) Moyal, Pascal; Tokro, Patrice; Bayram, Ahmet; Savopoulou-Soultani, Matilda; Conti, Eric; Eizaguirre, Matilde; Le Rue, Bruno
    The major pest of maize in Mediterranean Europe, the stem borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae), has a fragmented distribution, north and south of the Sahara. The present study aimed: (1) to clarify the uncertain taxonomic status of the Palearctic and sub-Saharan populations which were first considered as different species and later on as subspecies (Sesamia nonagrioides nonagrioides and Sesamia nonagrioides botanephaga) and (2) to investigate the origin of the Palearctic population which extends from Spain to Iran, outside what is considered typical for this mainly tropical genus. We reconstructed the evolutionary history of both populations using one nuclear and two mitochondrial genes. The sub-Saharan taxon was fragmented in two isolated populations (West and East) whose mitochondrial genes were distant by 2.3%. The Palearctic population was included in the East African clade and its genes were close or identical to those of a population from Central Ethiopia, where the species was discovered for the first time. Similarly, in Africa, the alleles of the nuclear gene were distributed mainly in two West and East clades, whereas some Palearctic alleles belonged to the West clade. The Palearctic population originated therefore from East and West Africa and is the progeny of the cross between these two African populations. The main species concepts were in agreement, leading to the conclusion that the three populations are still conspecific. In the surveyed regions, the species therefore does not include two subspecies but three isolated populations. The Palearctic population suffered from severe bottlenecks that resulted in the fixation of one East African mitochondrial genome and the large reduction in its genetic diversity compared to the African populations. The data suggest that natural colonization of the Palearctic region was more plausible than human introduction. The allelic distribution of the Palearctic population was similar to that of species that survived the last glaciation. It is concluded that the African populations expanded during the last interglacial, crossed the Sahara and mixed in North Africa where fixation of the East mitochondrial genome occurred. The species then colonized Europe westward through only one eastern entrance. The coalescent-based estimate of the time to the ancestor of the Palearctic population was 108 000 years, which is consistent with this scenario. (C) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 904-922.
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    Sub-lethal effects of two pyrethroids on biological parameters and behavioral responses to host cues in the egg parasitoid Telenomus busseolae
    (Academic Press Inc Elsevier Science, 2010) Bayram, Ahmet; Salerno, Gianandrea; Onofri, Andrea; Conti, Eric
    The present study was undertaken to investigate possible integration of synthetic pyrethroids with biological control of Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) by the egg parasitoid Telenomus busseolae Gahan (Hymenoptera: Scelionidae). The effects of two commonly used synthetic pyrethroids, deltamethrin (Decis Jet 15 EC) and cyfluthrin (Bayteroid 5 EC), on the parasitoid were studied. Lethal concentrations (LC25) were estimated for both insecticides, and their sub-lethal effects on some biological parameters and behavioral responses to different kairomonal cues mediating host location were investigated. Parasitoid females exposed to cyfluthrin (LC25) parasitized significantly fewer eggs than untreated females, whereas neither the level of emergence from parasitized eggs nor the sex ratio of the offspring was affected by the insecticides. None of the above biological parameters were significantly affected by deltamethrin (LC25). Both insecticide treatments reduced the longevity of the parasitoids. The effects of both insecticides (LC25) on the behavioral responses of parasitoid females to the sex pheromone of S. nonagrioides, which acts as a long-distance kairomone, were investigated in a Y-tube olfactometer. Cyfluthrin-treated parasitoids failed to respond to the host pheromone, whereas deltamethrin-treated females responded similarly to untreated females. In addition, sub-lethal effects of pyrethroids on parasitoid arrestment behaviors were evaluated in an open arena containing abdominal scales from virgin female moths, which are a source of short-distance kairomone for the parasitoid. No significant differences in arrestment behaviors (residence time, linear speed) were found. Based on our results, possible consequences of treating maize with cyfluthrin or deltamethrin on the effectiveness of surviving T. busseolae in the field are discussed. (C) 2009 Elsevier Inc. All rights reserved.