Temporal progress of teak rust in a tropical area of Tocantins State, Brazil

Abstract

Rust, caused by Olivea neotectonae, stands out as the main teak disease, causing premature defoliation regardless of the tree's growth stage. In this study, we aimed to assess the temporal progress of rust in adult teak plants in southern Tocantins State (Brazil). Both rust incidence and severity were evaluated and the disease progress curves were obtained, adjusting to monomolecular, logistic and Gompertz mathematical models. Data from incidence and severity were correlated with climate variables collected by the agrometeorological station located in the study area. Rust incidence reached 100% at 98 days after beginning of the evaluations (DBE). The highest severity (equal or above 75%) was observed at 147 DBE. There was a significant and negative correlation between severity and minimum temperature. The adjustment of the Gompertz model suggests that control measures should be aimed primarily to reduce the rate of disease progress. KEYWORDS: epidemiology, Tectona grandis, Olivea neotectonae Progresso temporal da ferrugem da teca em uma área tropical no Estado do Tocantins, Brasil RESUMOA ferrugem, causada por Olivea neotectonae, destaca-se como principal doença da teca, causando desfolha prematura em todos os estádios fenológicos da cultura. O objetivo do estudo foi avaliar o progresso temporal da ferrugem em plantas adultas de teca no sul do Estado do Tocantins. Avaliaram-se a incidência e severidade da ferrugem (escala de notas) e obtiveram-se curvas de progresso da doença, que foram ajustadas aos modelos matemáticos monomolecular, logístico e Gompertz. Correlacionaramse os dados de incidência e severidade com as variáveis climáticas coletadas na estação meteorológica, localizada na região do estudo. A incidência da ferrugem atingiu 100% aos 98 dias a partir do início das avaliações (DIA). A maior severidade (igual ou acima de 75%) foi observada aos 147 DIA. Houve correlação negativa e significativa entre severidade e temperatura mínima. O ajuste ao modelo de Gompertz sugere que medidas de controle devem ser tomadas objetivando reduzir a taxa de progresso da doença.

Temporal Progress of Candeia Rust Caused by Puccinia velata in Clonal Candeia Plantation (Eremanthus erythropappus (DC.) McLeisch)

“…However, in the months before the beginning of disease progression, such as February and March, there was high rainfall. In this case, the high rainfall combined with the high relative humidity observed before the increase in disease severity in the field favored the establishment of the pathogen in the area, since these conditions contribute to the germination of urediniospores to initiate infection [9]. In turn, the highest mean rainfall, recorded in December, coincided with the lowest mean disease severity.…”

“…Thus, the negative correlation observed between disease severity and monthly mean temperature shows that mild temperatures favor the incidence of fungal sporulation. Sales et al [9] stated that low temperatures can favor the disease because they increase the stress experienced by the plant, thus increasing its susceptibility to the pathogen, since these conditions favor the sporulation of the pathogen. In addition, Ruiz et al [22] observed correlations between the severity of P. psidii in Eucalyptus grandis and temperatures between 18 and 25 • C and high humidity.…”

“…This model was described by Vanderplank [18] for modeling diseases, who showed that the infection rate increases during the epidemic because it is not limited by factors such as the amount of host tissue. Sales et al [9] studied the temporal progression of teak rust and observed that the Gompertz model had the best fit to the data, indicating that control measures to reduce the disease progress rate are the most effective. In addition, Oliveira et al [26] obtained the best fit to bacterial leaf blight (Xanthomonas axonopodis) progression data with the Gompertz model for most of their studied clones.…”

“…Among them, rust caused by Puccinia velata [8] may become a limiting factor for the production of candeia due to the expansion of its planted area. This is because rusts in forest species are known to cause severe and premature defoliation, and the physiological damage reduces wood yield [9]. P. velata is described as occurring in trees over three years old and in adult leaves in the field [10], which may decrease plant growth due to nutrient removal and leaf area reduction resulting from the formation of signs of the pathogen's fungal structures and early leaf drop [11].…”

Extração de DNA e identificação molecular de Olivea neotectonae (T.S. Ramakrishnan & K. Ramakrishnan) isoladas de folhas de teca (Tecto-na grandis L.f)

“…Nas plantas infectadas observam-se manchas de coloração marrom escuro (necróticas) na face adaxial da folha e a presença de pústulas amarelas na face abaxial. No campo, a doença pode ocorrer tanto em plantas jovens quanto em plantas adultas, e o principal prejuízo da doença é a desfolha prematura da planta, que pode reduzir em até 30% no crescimento (Sales et al, 2017).…”