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Báo cáo khoa học: "Estimation des niveaux d’infestation passés de la tordeuse du sapin Choristoneura murinana (Hb.) (Lép., Tortricidae) par analyse rétrospective des pertes de feuillage et de croissance des arbres"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Estimation des niveaux d’infestation passés de la tordeuse du sapin Choristoneura murinana (Hb.) (Lép., Tortricidae) par analyse rétrospective des pertes de feuillage et de croissance des arbres. | Ann. Sci. For. 1988 45 4 357-381 Estimation des niveaux d infestation passes de la tordeuse du sapin Choristoneura murinana Hb. Lép. Tortricidae par analyse retrospective des pertes de feuillage et de croissance des arbres p. DU MERLE D. GÉRAUD avec la collaboration technique de E. ROBERT INRA Station de Zoologie forestiere Centre de Recherches d Avignon avenue A. Vivaldi F 84000 Avignon Summary Estimating the past annual activity of the fir budworm Choristoneura murinana Hb. Lep. Tortricidae through retrospective analysis of the foliage and growth losses of the trees. The budworm Choristoneura murinana has recently proved to severely damage silver fir Abies alba Mill. stands in the south of France. Understanding this situation perhaps only new apparently and assessing its implications would need to have informations on the past activity of the pest. Three criteria from trees likely to supply such data were tested the needle loss of the shoots the annual length increment of the branches and the annual radial increment of the trees. Observations were made in the departement of Ardèche in two plots of a mature silver fir stand infested by the budworm. Twenty dominant-codominant trees were selected in each plot. Branch samples were collected both from the top third and from the middle third of their crowns. Needle loss and defoliation estimates were based on rating of the shoots under consideration in percentage loss or defoliation classes. Radial growth was measured at breast height. One starting supposition was that estimating the respective needle loss percentages for the different age classes of shoots being only taken into account those shoots apparently not yet affected by the natural needle fall would give values approximately equal to those of the annual rates of budworm defoliation for the corresponding years. The use of such a method we call retrospective estimation of the defoliation was theoretically made possible by the conjunction of the following .