The aim of this study was to clarify the relationship between soybean leaf/plant age and the susceptibility to infection by Phakopsora pachyrhizi. Two studies were conducted in the greenhouse during the 2009/2010 season using the BRS 232 cultivar. The experimental design for Study 1 was fully randomized in a 2 x 3 factorial arrangement (phenological stage x age of the 4th, 5th and 6th trifoliate at the time of inoculation), and in Study 2, the experimental design was fully randomized with five treatments (T) and four replicates. The variables assessed were disease severity, number of lesions, uredinia per lesion, and viable spores. In Study 1, it was observed that disease severity was lower when the plant was in the growth stage V6 (11.4%), compared to the reproductive stage R4 (16.9%). The regression for disease severity and leaf age at the time of inoculation showed that older trifoliates on the plants in the reproductive stage exhibited higher severity. However, in Study 2, for trifoliates of the same age on plants of different ages, the trifoliates of younger plants were more susceptible to the disease. It was concluded that soybean plant susceptibility to soybean rust was directly proportional to the age of the trifoliate on a given plant and the phenological stage of the plant at the time of inoculation.

Despite the favorable edaphoclimatic conditions in Brazil, the production is limited due the many factors such as diseases. Root rot in the avocado is caused by the pathogen Phytophthora cinnamomi Rands. The disease is the main phytosanitary constraint in the avocado crop due to the susceptibility of main cultivars and the destructive power of pathogen (⁵, ²³, ²⁵). Among the management strategies are the use of tolerant rootstocks, acquisition or production of free pathogen seedlings, removal of cultural remains, planting in well-drained soils, balanced fertilization, as well as fungicide application and biological control (¹).