Dulce Regina Nunes Warwick

Outbreak of stem bleeding in coconuts caused by Thielaviopsis paradoxa in Sergipe, Brazil

In February of 2004, at “Plato de Neopolis”, Sergipe, Brazil, about 50 coconut plants were found bearing symptoms of a disease not yet recorded in Brazil. The trunk of diseased plants exhibited a reddish-brown or rust��colored liquid bleeding from scars. Inside the stem, the tissues under the lesions were rotting and turned brownish-yellow to black. Diseased palms had reduced growth and three to four months after the first symptoms were noticed the affected plants died. A fungus was isolated from diseased tissues and identified as Thielaviopsis paradoxa. Healthy plants were inoculated with the fungus and lesions developed demonstrating the pathogenicity of the isolate.

Stromata colonization of Sphaerodothis acrocomiae causal agent of the coconut large verrucosis by Acremonium persicinum

Stromata colonization of Sphaerodothis acrocomiae causal agent of the coconut large verrucosis by Acremonium persicinum The factors affecting the biological control of large verrucosis (Sphaerodothis acrocomiae) of coconuts (Cocos nucifera) with the utilization of the hiperparasite fungus Acremonium persicinum were studied. This hiperparasite is found mainly in the rainy season (April-august) colonizing stromata of large verrucosis as well as small verrucosis. On culture the fungus produces a fine mycelium, with single, small, hyaline conidium and on PDA the culture has a purplish color. The 10 conidia per ml were the smaller concentration, which gave a bigger colonization in the field trial. The application of the hiperparasite gives best results in the rainy season and when performed i1n the afternoon. As lixas do coqueiro (Cocos nucifera L.) sao colonizadas naturalmente por fungos hiperparasitas. Na tentativa de viabilizar o controle das mesmas atraves da aplicacao controlada de agentes reproduzidos em laboratorio, avaliaram-se diferentes formas de utilizacao de Acremonium persicinum (Nicot.) W. Gams, em nivel de campo. Em um plantio comercial de coqueiro hibrido (anao vermelho do brasil x gigante do brasil), com dois anos de implantacao e naturalmente atacado pela lixa grande, foram avaliados os parâmetros preliminares para a utilizacao do controle biologico no campo. Inicialmente foram utilizados pulverizacoes com 1 x 10, 1 x 10, 1 x 10 conidios por ml. as 9 h da manha e vespertina (apos as 16 h). Foram feitas aplicacoes quinzenais durante todo o ano de l997. A avaliacao contou da coleta de 12 foliolos das tres ultimas folhas para a contagem de estromas parasitados e nao parasitados, 15 dias apos a aplicacao do hiperparasita. A aplicacao matinal de A. persicinum no campo nao teve resultado satisfatorio, tambem a aplicacao em meses secos, nao resultou em uma colonizacao efetiva dos estromas pelo hiperparasita (Tabela 1). Verificou-se ainda que a concentracao de 10 conidios por ml foi a que proporcionou o melhor resultado durante o experimento realizado (Tabela 1). O sucesso do biocontrole de patogenos da parte aerea das plantas e parcial e limitado quando comparados com o biocontrole de patogenos causadores de doencas do sistema radicular. A baixa eficiencia do controle biologico dos patogenos foliares depende ainda de um bom agente veiculante e do impacto do meio ambiente. TABELA 1 Percentagem media de estromas colonizados de lixa grande, em foliolos coqueiro (Cocos nucifera), duas semanas apos a aplicacao do fungo hiperparasita Acremonium persicinum Tipo de aplicacao do hiperparasita Estromas colonizados (%). 10 5 Estromas colonizados (%). 10 6 Estromas colonizados (%) .10 7 Periodo seco, matinal 4% 12% 17% Periodo seco, vespertino 13% 15% 20% Periodo chuvoso, matinal 15% 16% 19% Periodo. chuvoso, vespertino 28% 45% 68% 00072 NOTAS FITOPATOLOGICAS / PHYTOPATHOLOGICAL NOTES

Spatial and temporal analysis of stem bleeding disease in coconut palm in the state of sergipe, Brazil

Stem bleeding disease (resinosis) of coconut palm is caused by Thielaviopsis paradoxa and is very important in the state of Sergipe, Brazil. Understanding the epidemiological behavior of the disease is essential for establishing more efficient control strategies. Thus, we characterized the temporal progression and spatial distribution of stem bleeding in a commercial orchard under conditions of natural infection in the area of Neopolis, Sergipe. Three plots with 729 plants each were selected and evaluated every two months for stem bleeding incidence. In the temporal analysis, the monomolecular model gave the best fit to data on disease incidence, as it accurately showed the temporal dynamics of the disease during the experiment period. The spatial pattern of stem bleeding varied over time, with initial infections presenting random pattern and then evolving to aggregate pattern during evaluations. This indicates that the disease may have originated from the pathogen survival structures, followed by auto infections caused by dissemination from plant to plant, either by humans, by contact between roots, or by the vector Rhynchophorus palmarum.