EPIDEMIOLOGICAL ASPECTS OF ROOT-ROT OF \u2018ERVA-MATE\u2019 ( Ilex paraguariensis )

A podrid\ue3o-de-ra\uedzes da erva-mate, causada por Fusarium spp., Rhizoctonia sp. e Pythium sp., \ue9 a principal doen\ue7a da cultura e causa s\ue9rios preju\uedzos em viveiro e a campo. No entanto, existem poucos estudos referentes \ue0 epidemiologia dessa doen\ue7a. Assim, o presente trabalho teve por objetivo estudar e descrever os principais aspectos epidemiol\uf3gicos relacionados \ue0 podrid\ue3o-de-ra\uedzes da erva-mate em viveiro e a campo. Para isso, foram demarcados para estudo ervais e viveiros localizados na regi\ue3o alta do Vale do Taquari - RS, nos quais se procedeu a coleta de flores, frutos, sementes, pl\ue2ntulas, mudas e substrato para an\ue1lises laboratoriais. Observou-se que as flores podem ser a porta de entrada dos pat\uf3genos no patossistema, pois 80% delas apresentaram contamina\ue7\ue3o por Fusarium sp. e 15% por Rhizoctonia sp. Al\ue9m disso, o m\ue9todo de obten\ue7\ue3o e estratifica\ue7\ue3o das sementes, utilizado pelos viveiristas, contribuem para o aumento da contamina\ue7\ue3o, chegando a 100% das sementes no momento da semeadura. Observou-se, tamb\ue9m, que as mudas podem estar contaminadas, mesmo n\ue3o apresentando sintomas e, ao serem replantadas a campo, venham a contaminar \ue1reas livres dos pat\uf3genos. Os testes de patogenicidade com alguns isolados mostraram sua capacidade em causar a doen\ue7a.The root-rot of erva-mate, caused for Fusarium spp., Rhizoctonia sp. and Pythium sp., is the main disease of the culture and causes serious damages in nurseries and forest stands. However, few studies exist regarding to the epidemiology of this disease. Thus, the present work studied and described the main epidemic aspects related to erva-mate root-rot in nurseries and forest stands. For that, nurseries and forest stands were chosen for studies in Vale do Taquari, RS state, where flowers, fruits, seeds, plantlets, seedlings and soil were collected for laboratory analyses. It was observed that the pathogens can enter in the patho-system through the flowers, because 80% of them presented contamination of Fusarium sp. and 15% of Rhizoctonia sp. Moreover, the obtaining method and stratification of the seeds, used in the nurseries, contribute to the increase of contamination, reaching 100% of the seeds in the moment of sowing. It was also observed that contaminated seedlings may be symptomless and, after transplanting in the field, contaminate pathogen free areas. Pathogenicity tests with some isolates showed their capacity of causing the disease