Host location in Trichogramma cacoeciae (Hymenoptera, Trichogrammatidae)
Parasitic
wasps of the genus Trichogramma spp. are well known as a limiting
factor for the grape berry moths Lobesia botrana Den. & Schiff.
and Eupoecilia ambiguella Hb. (Lepidoptera: Tortricidae) in the laboratory
and in house-vineyards.
Grape berry moths (GBMs) are the economically most important pests
in German vineyards. They cause considerable losses in both quality
and yield of grapevine. The larvae of both species thereby cause
direct damage by feeding on the berries and indirect damage by
leading to infections of the berries by the fungi Botrytis cinerea.
Biological control of GBM gains more and more importance as the
use of chemical pesticides declines. Therefore no other parasitoid
in the world has been used as extensively as Trichogramma for integrated
pest control. The development of a rational and most economical
mass rearing method by means of Sitotroga cerealella as an alternative
host, led to an intensification of the field use of these parasitic
wasps in numerous crops. Trichogramma are solitary endoparasitoids,
they exploit eggs of more than 400 hosts mostly Lepidopteran species,
like GBM, on a large variety of plants.
My research now focuses on the mechanism of host finding behaviour
of Trichogramma cacoeciae on its two hosts Lobesia botrana and
Eupoecilia ambiguella. Because host age is said to influence the
ability to detect a host in some other species, the first step
was to find out, whether egg age has an effect on the host location
of T. cacoeciae. This was done in Y-tube experiments as well as
in biological tests with a flying arena. The next step now is to
find out witch substances (kairomone) are used by the parasitoid
to locate eggs of their host. Therefore I analyse extracts from
eggs of different ages with GC-MS. Than the extracts as well as
the synthesised substances will be tested in the Y-tube olfactometer.
This work is done in cooperation with the National Wine Growing
Institute Freiburg and AMW-Nuetzlinge GmbH in Pfungstadt.
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