Evaluation of some Trichogramma species with respect to biological control of Eupoecilia ambiguella Hb. and Lobesia botrana Schiff. (Lep., Tortricidae)
1993
Castaneda-Samayoa, O. (Forschungsanstalt Geisenheim (Germany). Inst. fuer Phytomedizin und Pflanzenschutz) | Holst, H. | Ohnesorge, B.
Four Trichogramma species were tested from 1986 to 1989 in field and laboratory experiments at Geisenheim (Rheingau, FRG) for their usefulness in biological control of grape tortricids. The following results were otained: A survey of naturally occuring egg parasitoids by means of 'trap cards' showed that only T. evanescens was present. It appeared during three distinctly separated periods which probably corresponded to the generations. Only the 1st and the last generations coincided with the oviposition periods of the grape tortricids. - Field trials for biological control with T. cacoeciae, T. embryophagum and T. dendrolimi yielded varying results; the damage reduction ranged 22,5% to 83,3% T. cacoeciae was, on the average, the most efficient species; T. embryophagum was least efficient. In the laboratory, all three species attacked eggs of grape tortricids almost equally well; only T. dendrolimi was slightly better than the others. There was no preference for one of the two tortricid species, but eggs, which were older than 2 days, were attacked considerably less than freshly deposited eggs. Rejection of eggs occurred in most cases during the act of 'drumming', but T. dendrolimi withdraw often during the act of 'drilling', causing in this way additional mortality. - T. cacoeciae and T. dendrolimi exhibited in field experiments a superior capacity for dispersal than the two other species, but T. dendrolimi showed a clear preference for the upper parts of the vines where hardly grape totricid eggs can be found
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