Effets de l'accroissement provoqué du niveau de population de la Tordeuse du Mélèze Zeiraphera diniana Guenée (Lep., Tortricidae) au cours de la phase de régression dans un massif forestier du Briançonnais
Auteurs : Auer (Christian), Charles (Pierre-Jean D.), Goussard (Francis) et Roques (Alain)
Année de publication : 1981
Publication : Journal of Applied Entomology (= Zeitschrift für Angewandte Entomologie)
Volume :
92
Fascicule : 3
Pagination : 286-303
Résumé :
he cyclic fluctutaions of populations of the larch bud moth, Z. diniana Guenede (Lepidoptera. Tortricidae) were studied in the Brianconnais (French Alps) since 1959. Two large-scale manipulations by Bacillus thuringiensis preparations were performed, resulting in immediate [control] efficiency, but failed to develop long-term changes in the cycle. In June 1974, the population of Z. diniana was in the 2nd yr of the postgradation stage of its fluctuation cycle in the 650 ha larch forest of Montgenevre, with a relative density of 0.31 larva /kg of larch twigs. At least 6000 moths were released in July-Aug. 1974, by introducing 35,000 pupae, uniformly distributed through the forest in cages and it was assumed that the entomophagous parasitoids which could be released simultaneously are limited to 1 spp. of Tachinidae in negligible numbers. The neighboring larch forests of the rivers Claree (or Vallee de Nevache) and Guisane were used as untreated controls. During the following 5 yr, the larval populations of Z. diniana were counted in these 3 valleys. The artificial increase of the population was followed by an immediate end to the postgradation stage in the forest of Montgenevre, by an accelerated stage of progradation and by a less intense outbreak and defoliation during Larval parasitism rate was maintained to a level above normal. This simple ecological manipulation of the cycle of Z. diniana seems useful as a future control techniques