Bark-beetle parasitoids population surveys following storm damage in spruce stands in the Vosges region (France)
Auteurs : Hougardy (Evelyne) et Grégoire (Jean-Claude)
Année de publication : 2001
Publication : Integrated Pest Management Reviews
Volume :
6
Pagination : 163-168
Résumé :
This paper presents the results of a long-term study designed to follow the population dynamics of hymenopteran parasitoids associated with Ips typographus L. (Coleoptera: Scolytidae) in northeastern France (Alsace and Vosges) in spruce stands devastated by the December 1999 storms. Population densities were estimated by periodic samplings in the pre-emerging insect populations developing under the bark of attacked trees. Data were collected between July 2000 and October 2001. I. typographus population density (per m2 ) increased respectively by 28%, 105%, and 212% in one year in the three sites surveyed. Six hymenopteran ectoparasitoids were found: Coeloides bostrichorum Giraud and Dendrosoter middendorffi Ratzeburg (Hymenoptera: Braconidae); Rhopalicus tutela (Walker), Roptrocerus xylophagorum (Ratzeburg), Roptrocerus mirus (Walker) and Dinotiscus eupterus (Walker) (Hymenoptera: Pteromalidae). After two years, the parasitoid populations increased in terms of average density but parasitism ratesremained at a relatively low level, ranging from 0% to 40%, with 60% of the trees having a parasitism rate below 5%. Data outlined the recurrent coexistence of competing parasitoid species.