Toxicity and sublethal effects of an insecticidal soap on Aphidius colemani (Hymenoptera: Braconidae).
BACKGROUND
The effects of an insecticidal soap on the survival, fitness and behaviour of an aphid parasitoid wasp, Aphidius colemani (Viereck), were studied in the laboratory. The LC(50) (soap concentration causing 50% mortality 24 h after treatment) was determined. The survival of parasitoid larvae (% adult emergence), fitness (tibia length of adults) and number of eggs produced per female parasitoid that survived in third- and fourth-instar aphids treated with insecticidal soap LC(50) were also assessed. The LC(50) for third- and fourth-instar aphids was determined to be 3.25 g L(-1). Acceptance by female parasitoids of aphids that survived their LC(50) was also tested.


RESULTS
The soap concentration causing 100% mortality in adult wasps 24 h after treatment was 17.5 g L(-1). The LC(50) was 2.75 g L(-1). Soap did not have any effect on the survival of parasitoid immatures or on the fitness or number of eggs produced per female parasitoid. Wasps that were in contact with treated aphids did not oviposit as much in them as in untreated aphids, indicating that female parasitoids detected aphids treated with insecticidal soap.


CONCLUSIONS
These data suggest that aphid parasitoids released following treatment with insecticidal soap are likely to accept a lower proportion of the surviving aphids. Biological control programmes could be ameliorated by soap applications if the latter were made 1 day before the release of wasps in the greenhouse.
Tremblay
Eléonore
E
Agriculture et AgroAlimentaire Canada, Centre de Recherche et de Développement en Horticulture, Saint-Jean-sur-Richelieu, Québec J3B 3E6, Canada. tremblayel@agr.gc.ca
Bélanger
André
A
Brosseau
Marcel
M
Boivin
Guy
G
D000818:Animals; D001042:Aphids / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects*; D016009:Chi-Square Distribution; D005260:Female; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D007928:Lethal Dose 50; D008297:Male; D010058:Oviposition / Q000187:drug effects; D012915:Soaps / Q000633:toxicity*; D014863:Wasps / Q000187:drug effects* / Q000502:physiology; D015053:Zygote / Q000187:drug effects*
D007306:Insecticides; D012915:Soaps