Some factors stimulating oviposition by the oophagous parasitoid Trichogramma brassicae Bezid. (Hym., Trichogrammatidae) in artificial host eggs
1993
Grenier, S. (Institut National de Recherches Agronomiques (INRA), Villeurbanne (France). Lab. de Biologie Appliquee) | Veith, V. | Renou, M.
The development of some Trichogramma species is possible in artificial conditions, but the number of eggs laid by females is often reduced compared to those laid in natural host eggs. Cupules made in a plastic membrane (2 mil) and filled with artificial medium containing hemolymph from Mamestra brassicae pupae were surface treated with pure solvent, Ostrinia nubilalis scale extract, or a mixture of compounds previously identified in O. nubilalis egg masses, in order to improve the oviposition performance of Trichogramma brassicae. An egg plate consisted in 54 cupules. Two day old females of T. brassicae were allowed to lay their eggs for 24 hours. Pure solvent alone stimulated the oviposition by modification of the structure of the membrane surface. O. nubilalis scale extract significantly increased the number of eggs laid (15 or 2.5 times, respectively in comparison with control or solvent). A blend of saturated hydrocarbons defined by Renou et al. (1992), stimulated the oviposition in a similar way as the extract did. If the solutions were deposited on a part of the egg plate, 77 to 88% of the eggs were laid in the treated cupules. The extract of blend acts as contact kairomones and they will be useful to improve the oviposition of T. brassicae, permitting an increase of adult yield in artificial conditions
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