CONICET | Buscador de Institutos y Recursos Humanos

Austrocedrus chilensis is an indigenous Cupressaceae of the Patagonian Andes forests in southern Argentina and Chile that suffers a disease called ?mal del ciprés?. Phytophthora austrocedrae, a new Phytophthora species, was recently shown to be the main cause of the disease. The progressive withering and subsequent defoliation of the tree, which finally dies, has traditionally been considered the main symptom. Other symptoms more specifically associated with P. austrocedrae include basal resinous exudates and red-brown necrotic lesions in the inner bark extending up the bole from killed roots. Traditionally, it was thought that crown transparency was a suitable measure of the health of a tree. Nevertheless, some contradictory observations make such a supposition doubtful and it is difficult to assess the extent of disease in a tree or a stand from this symptom alone. Since an accurate method for evaluating the health of affected trees is essential for establishing management and conservation strategies in affected forests, an evaluation of symptomatology and its association with tree health was done. The aims of this work were to analyze the association between aerial symptoms and vitality and to adjust the method used for determining vitality of trees affected by ?Mal del Ciprés?. Vitality was defined as the proportion of the tree circumference at the root collar that had necrotic lesions in the inner bark. Sixty trees, in three different health classes, of a stand affected by ?mal del ciprés? were evaluated. Percentage of defoliation was estimated visually. The pattern of defoliation, the presence of yellow or red leaves in the crown, cankers and resinous exudates in the stem, and other features that could be related to vitality were also recorded. Bark was removed to expose inner bark and the vitality at the root collar was determined as the percentage of the perimeter with dead tissues. Then the root system was excavated to expose roots in a perimeter of 1m from the base of the tree. Bark of main roots was removed and vitality of each root was evaluated as the percentage of tissues dead/affected. Vitality of the entire root system was estimated as the total percentage of affected tissues of main roots. The association between aerial symptoms and tissue vitality was evaluated through a correlation analysis. This work presents the results of the study and a discussion on the reliability of aerial symptoms for estimating vitality of trees affected by the ?Mal del Ciprés?.

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