ECOLOGY OF DISEASES IN FOREST NURSERIES IN NEUQUEN, ARGENTINA SN BLUMENFELD RESANOR-NEUQUEN, Universidad Nacional del Comahue, C.C. 85, 8303 Cinco Saltos, Rio Negro, Argentina. Background and objectives This paper reviews the main disease problems in the argentine andino-patagonian forest nurseries. Some of the major diseases that are covered include damping-off, root rots, cankers, stem and branches dieback and shoots dieback. All of them are associated with particular ecological conditions. The climate of the area we are concerned with is characterized by short dry summers, very cold winters and rainy falls and springs. The summer affects the life cycle of pathogenic fungi and reduces the incidence of foliar diseases while the cold winters and rainy springs result in premature early growth and possible damage from late frosts. Nurseries are too small to be economically viable or are located in unsuitable soils. Often lacks adequate professional training. These deficiencies affect both the quantity and quality of the seedlings, having a negative impact on forest production. Materials and methods Floristic, taxonomic and plant pathology studies were made according to standard methods (1), (2). Biodiversity and ecological distribution were considered in relation to the type of vegetation. When it was possible, axenic cultures of pathogenic fungi were obtained. Results and conclusions A catalogue of 36 forest nursery diseases has been recorded. A collection of about 20 strains were obtained. Damping-off affects containerized seedlings of Pinus and broadleaf species. Pythium spp. and Rhizoctonia solani were the most frequently isolated pathogens. Terminal bud dieback in Pinus spp. and foliar blight of poplars were the major problems in nurseries located in areas with longer hot summers. Control and protection measures are given. References 1. Sinclair WA, Lyon HH and Johnson WT, 1987. Diseases of trees and shrubs. Cornell University Press, 575 p. 2. Sutherland JR and Glover SG, 1991. Proceedings of the first meeting of IUFRO Working Party S2.07-09 (Diseases and Insects in Forest Nurseries), pp. 1-228.