Eucalyptus scab and shoot malformation: A new and serious foliar disease of Eucalyptus caused by Elsinoe necatrix sp. nov.

Abstract

In 2014, a new and serious leaf and shoot disease of unknown aetiology appeared in Eucalyptus plantations of North Sumatra, Indonesia. The disease is characterized by black necrotic spots that initially appear on young leaves and petioles, which become scab‐like as the lesions age. Infected trees respond to infection by producing shoots with small leaves that commonly appear feathered. Fruiting structures typical of most foliar pathogens are not seen, but using scanning electron microscopy (SEM), fungal spores are evident and associated with the scab‐like structures. Using culture‐dependent methods, cultures resembling a species of Elsinoe were isolated from the lesions. DNA sequence comparisons for four gene regions, as well as morphological observations, showed that the fungus is an undescribed species in Elsinoe, for which the name Elsinoe necatrix sp. nov. is provided. Pathogenicity trials on a Eucalyptus clone with the Elsinoe species resulted in scab‐like structures similar to those observed under field conditions and the fungus was easily reisolated from the resulting lesions. This study includes a description of the pathogen and characterization of the disease, for which the name Eucalyptus scab and shoot malformation is suggested.

IMA genome‑F17

“…Members of these necrotrophic fungal pathogens are globally distributed and infecting approximately 70 hosts including important forestry, agricultural and horticultural crops as well as ornamental plants (Fan et al 2017 ; Marin-Felix et al 2019 ). Important diseases include the citrus scab pathogens Elsinoë fawcettii and E. australis (Chung 2011 ), the causal agent of grapevine spot anthracnose E. ampelina (Li et al 2021 ), and the recently described E. necatrix that causes a devastating scab and shoot malformation disease on plantation-grown Eucalyptus (Pham et al 2021 ).…”

“…Eucalyptus scab and shoot malformation was first reported in North Sumatra, Indonesia, in 2014 (Pham et al 2021 ). The disease is characterized by black necrotic spots that first emerge on young leaves and petioles, which become scab‐like as the lesions age.…”

Botryosphaeriaceae diversity on Eucalyptus clones in different climate zones of Indonesia

“…It has also been shown as one of the more aggressive pathogens of Eucalyptus in plantations (Li et al, 2018). In this study, L. theobromae was found on both trees that were affected by Elsinoe necatrix (Pham et al, 2021) or that were insect-damaged. These trees included eight clones in both North and Central Sumatra.…”

“…In this study, L . theobromae was found on both trees that were affected by Elsinoe necatrix (Pham et al, 2021) or that were insect‐damaged. These trees included eight clones in both North and Central Sumatra.…”

“…(Miridae) or scab and shoot malformation caused by the fungal pathogen, Elsinoe necatrix N.Q. Pham et al (2021). In Central Sumatra, most sampled trees displayed damage due to the wood-boring moth, Polyphagozerra coffeae (Cossidae) (Figure 1).…”