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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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    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.