The discovery of Cryphonectriaceae and more specifically species related to the Eucalyptus canker pathogen Chrysoporthe cubensis on shrubs and trees in the Melastomataceae, has deepened our understanding of relevant, and potentially globally threatening tree pathogens. Recent isolations of Cryphonectriaceae associated with cankers on Tibouchina spp. in Brazil gave rise to an apparently undescribed species of Chrysoporthe associated with stem and branch cankers that lead to tree death. Cultures of this fungus were subjected to phylogenetic studies based on sequences for the ITS and β-tubulin gene regions. These analyses revealed a novel taxon that is described here as Chrysoporthe puriensis sp. nov., having both sexual and asexual states. Pathogenicity tests on two species of Tibouchina (T. granulosa, T. heteromalla) and hybrids of Eucalyptus grandis x E. urophylla showed that Chr. puriensis can infect and cause disease on all of these trees. It is clearly not only damaging on native Tibouchina spp. where environmental conditions are conducive to disease development, but also potentially threatening to non-native Eucalyptus spp., which form the basis of a major plantation forest industry.

The supply of nutrients in balanced proportions leads to greater crop yields and represents an alternative practice for the management of plant diseases. Accordingly, we investigated the effect of the doses of and the nutritional balance between calcium (Ca) and potassium (K) on the severity of leaf spot and defoliation caused by the fungus Calonectria pteridis. Moreover, the effect of the treatments on the growth of interspecific hybrid eucalyptus clone seedlings (Eucalyptus grandis Hill ex Maiden × E. urophylla S.T. Blake), which are highly susceptible to the disease, was evaluated. The 25 treatments comprised combinations of one of five doses of Ca (1.2, 3.0, 6.0, 9.0 and 12.0 mmol L−1) with one of five doses of K (0.8, 2.0, 4.0, 8.0 and 12.0 mmol L−1) and five replicates of each treatment were included in the study. The supply of high concentrations of K favoured C. pteridis infection and resulted in high disease severity, although defoliation was not observed. However, the supply of both nutrients in excess (12.0 mmol L−1 Ca × 9.0 mmol L−1 K) resulted in a higher disease severity and an increased defoliation percentage (82 and 64%, respectively). Defoliation not associated with Calonectria leaf blight disease was observed with the imbalanced treatments, that is, the treatments combining a low concentration of one nutrient and an excess concentration of the other nutrient. The supply of K at a level near the standard dose (6 mmol L−1) and of Ca at a dose above 4 mmol L−1 (standard dose) ensured high mean values for the morphological variables root and shoot biomass, plant height and chlorophyll a and b contents. These treatments also resulted in low disease severity and defoliation percentages, indicating that a balanced supply of Ca and K ensures reductions in disease severity and defoliation and contributes to higher growth.

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The genus Quambalaria includes several important pathogens of Eucalyptus and Corymbia spp., mainly those that cause leaf and shoot blight. The species Quambalaria eucalypti has been reported to be an aetiological agent of this disease in Brazil only in nurseries involved in the production of Eucalyptus minicuttings, where climatic conditions are more favourable for the pathogen. The aim of this study was to identify the pathogen that causes a similar disease in young Eucalyptus trees. For this, we used morphological characteristics, pathogenicity tests and DNA sequence data. Sequences of four isolates obtained from leaves and cankers were compared to 17 sequences deposited in GenBank. Twenty‐one isolates were subjected to multilocus analyses of internal transcribed spacer (ITS) and rDNA large subunit (LSU) sequence information. The resulting consensus tree showed that isolates in this study could be grouped with Q. eucalypti into one distinct clade, and the morphological characteristics were similar to those described in the literature. The pathogenicity was confirmed, and the pathogen was re‐isolated from inoculated plants, confirming Koch's postulates. This is the first record of Q. eucalypti causing leaf and shoot blight on young Eucalyptus plants in field conditions in Brazil. The presence of this disease in nurseries and its occurrence in the field is cause for alarm in Eucalyptus breeding programmes in Brazil.