Summary A leaf spot pupunha (Bactris gasipaes H.B. K.) was observed in Manaus, Brasil reducing plant vigor in the nursery. The causal agent was Identified as Colletotrichum gloeosporioides Penz. The disease Is characterised initially by Irregular leaf spots starting at the leaflet edge and expanding towards the leaflet center. Artificial inoculation confirmed Its pathogenicity. This is the first reported occurrence of leaf spot of pupunha caused by C. gloeosporioides In Brazil.

Resumo Avaliou-se, em Manaus, AM, a intensidade do ataque de Alternaria porri em híbridos e cultivares de cebola (Allium cepa L.) A doença ocorreu naturalmente e efetuaram-se as observações ao final do ciclo vegetativo. Considerou-se o total de plantas avaliadas como 100% e as plantas, de acordo com a porcentagem de infecção, foram enquadradas nas seguintes classes: I ((0-10%); II (10-30%); III (30-50%); IV (50-70%) e V (> 70%). O híbrido (Px-76) foi o único a apresentar plantas na classe com 0-10% de infecção. Os cultivares Barreiro Roxa, Pira Lopes, Pira Tropical, Pira Rosa e Pira Ouro e o híbrido Px-25 mostraram um comportamento semelhante com 39,03 a 48,17% das plantas enquadradas na classe III (30-50% de infecção). O híbrido Px-31 foi o mais suscetível, apresentando 50% das plantas na última classe, ou seja, com valores de infestação superiores a 70%.

Summary Susceptibility to Alternaria porri was evaluated in onion (Allium cepa L.) hybrids and cultivars in Manaus, AM. The desease occurs naturally and observations were made at the end of the vegetative cycle. Plants were grouped in classes as follows depending on % infection: I (0-10%); II (10-30%); III (30-50%); IV (50-70%) and V (> 70%). The (Px-76) hybrid was the only one that had plants in the classe I. Most plants (39,03-18,17%) of Barreiro Roxa, Pira Lopes, Pira Tropical, Pira Rosa and Pira Ouro cultivars and the (Px-25) hybrid showed 30-50% infection. The (Px-31) hybrid was the most suscetible, with 50% of the plants being more than 70% infected.

Resumo Procurando determinar a concentração de esporos do fungo Thielaviopsis paradoxa agente etiológico de podridão negra em frutos de pupunha (Bactris gasipaes H.B.K.), inocularam-se frutos com e sem pedúnculo nas concentrações de 10 7 , 20 5 , 10 3 , 10' esporos/ml. Observou-se que os frutos que apresentam pedúnculo necessitam de uma concentração de 10 7 esporos/ml para que 100% destes sejam infectados. Os que apresentaram pedúnculo e sementes foram mais sensíveis à infecção. No controle in vitro testaram-se os fungicidas Benomyl, Triadimefon, Zineb e Maneb a 25, 50, 75 e 100ppm em meio BDA. A melhor eficiência no controle de doença foi obtida com Benomyl em todas as concentrações estudadas, Triadimefon não foi eficiente a 100ppm e os demais fungicidas não controlaram o crescimento do fungo.

Summary Pupunha (Bactris gasipaes H.B.K.) is a palm distributed in almost all the humid tropics at south America and Central America. The pupunha fruits are rich in starch, lipids and proteins. This crop presents a serious problem: after harveste the fruits are subject to the attack of black rot, caused by the fungus Thielaviopsis paradoxa. The fruit pulp becomes dark and smells as fermented In order to determine the spore concentration that induces black rot in pupunha, fruits with and without peduncle were inoculated with spore concentrations of 10 7 , 10 5 , 10 3 e 10' spores/ml. Fruits with peduncles were observed to require concentrations of 10 7 spores/ ml to attain 100% fruit infection. The fruits with seed showed greater sensibility to infection. In another trial the fungicides: Benomyl, Triadimefon, Zineb and Maneb, were tested in vitro at the concentrations of 25, 50, 75 e 100ppm in PDA medium (potato-Dextrose-Agar). Benomyl inhibited totally the growth of the fungus at all concentrations used. Triadimefon showed some efficiency at 100ppm, while Zineb and Maneb were inefficient at all concentrations tested.