Parasitierungsversuche mit Trichogramma dendrolimi Mastsumura und Trichogramma maidis Pintureau et Voegelé (Hymenoptera, Trichogrammatidae) beim Einbindigen Traubenwickler, Eupoecilia ambiguella Hübner (Lepidoptera, Tortricidae)

Trials for parasitization the Grape berry moth, Eupoecilia ambiguella Hb. by the egg parasites Trichogramma dendrolimi Mast, and T. maidis Pint, et Voeg. Laboratory studies were conducted to examine whether age and fertility of the eggs of the Grape berry moth, Eupoecilia ambiguella are factors which influence the parasitization by the egg‐parasite Trichogramma dendrolimi. Eggs younger than four days (head capsule not visible) are equally attractive and of the same quality for the parasite independent of whether they are sterile or fertile. Parasitization rate decreases drastically in eggs which are older than four days, and it drops to almost zero when the black head capsule has developped. The impact of a fungicide mixture consisting of Bayleton WP5 0.05 % and Viti‐Folpet 0.3 % (active ingredients Triadimefon, Folpet and Copper) on the parasitism was examined under laboratory conditions. One method consisted in applying the fungicide on vine leafs prior to the oviposition by the pest insect. With the second method, Grape berry moth eggs were layed on untreated leafs and the fungicide was applied afterwards, thus, not only the leaf surface but also the eggs were covered with a fungicide layer. Neither of both treatments decreased the parasitization rate significantly. Field studies were carried out for assessing the impact of climatic factors on the parasitism by T. dendrolimi. A strong linear relationship (rank correlation coefficient = 0.94) exists between maximum temperature and parasitization rate. Other climatic factors (windspeed, rain, sunshine) influenced parasitism indirectly only. Two field experiments with T. maidis gave useful information about the potentiality of inundative releases of trichogrammatids in vineyards. The results obtained are encouraging, though, the parasitization rates underlie strong variation, ranging from 22 % to 66 %. Zusammenfassung Unter Laborbedingungen konnten wichtige Fragen im Zusammenhang mit Trichogramma ‐Versuchen beim Einbindigen Traubenwickler, Eupoecilia ambiguella , beantwortet werden: — Einfluß des Wirtseialters sowie steriler und fertiler Wirtseier auf die Parasitierung durch Trichogramma dendrolimi; — Nebenwirkung von unter und über den Wirtseiern applizierten Fungizidbelägen auf den Parasitierungserfolg. In Feldversuchen konnte, dank künstlicher Eiinfektion auf Rebblättern der Traubenzone mittels eingebeutelter Traubenwickler, der Einfluß unterschiedlicher Witterungsbedingungen auf den Parasitierungserfolg durch T. dendrolimi geprüft werden. Diese methodisch einfache Versuchsanordnung erlaubt in kurzer Zeit Trichogrammen unter Freilandbedingungen zu prüfen, ohne auf das zeitlich limitierte Auftreten des natürlichen Wirts angewiesen zu sein. Praxisversuche zur Bekämpfung der 2. Generation des Einbindigen Traubenwicklers, E. ambiguella , mit T. maidis brachten nur Teilerfolge, jedoch wichtige Hinweise für künftige Freilandversuche.