Ichneumonoideos (Hymenoptera) parasitoides del complejo de orugas cortadoras en pasturas de alfalfa (Medicago sativa L.) en la Argentina Central

Abstract

The knowledge about the role of natural enemies is crucial for integrated pest management systems. Parasitoids are considered most important for biological control, although the quantitative dimension of their effect on hosts is not always known. The objective of the present study was to survey the parasitoids of cutworms in the northeastern area of La Pampa Province, Argentina. The field work was conducted during four years (1999 to 2002). Larvae of Agrotis gypaetina Guenée, A. malefida (Guenée) and Peridroma saucia (Hübner) (Lepidoptera: Noctuidae) were collected in a fortnightly interval in alfalfa pastures, in order to establish the incidence of hymenopterous parasitoids in three areas of the eastern physiographic area of La Pampa, Argentina. These larvae were kept in breeding laboratory and fed with artificial diet until emergence of the parasitoids. The larvae were then identified and quantified. Parasitoid species of four genera of Ichneumonidae were found: Alophophion sp. Cushman (Ophioninae), Campoletis sp. Förster (Campopleginae), Thymebatis spp. Brèthes (two species) and Eutanyacra sp. Cameron (Ichneumoninae); and one species of Braconidae: Glyptapanteles bourquini (Blanchard) (Microgastrinae). New host species for Alophophion, Thymebatis and Eutanyacra were recorded. Alophophion was responsible for 80% of the parasitoidism, was present in all the regions studied and parasitized all the species of cutworm found.