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Limited protection of the parasitoid P achycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression
Author(s) -
Cossentine J.E.,
Ayyanath M.M.
Publication year - 2017
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/eea.12592
Subject(s) - parasitoid , spinosad , biology , host (biology) , pupa , drosophila suzukii , toxicology , parasitism , larva , zoology , botany , ecology , drosophila melanogaster , drosophilidae , pesticide , gene , biochemistry
Abstract Laboratory trials were conducted to determine whether the spotted wing drosophila, D rosophila suzukii ( M atsumura) ( D iptera: D rosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid P achycrepoideus vindemiae ( R ondani) ( H ymenoptera: P teromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D . suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P . vindemiae female mortality (83%) occurred within 24 h of exposure to D . suzukii pupae treated with 10 mg a.i. l −1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. P achycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P . vindemiae survival and emergence was recorded when parasitized D . suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P . vindemiae parasitism into a sustainable D . suzukii management program is not compatible with spinosad treatments, although P . vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.