The occurrence of gummosis on invasive acacia decurrens after mount merapi eruption in Yogyakarta, Indonesia

Abstract

Gummosis on Acacia decurrens, an invasive tree species that was established in Merapi Volcano National Park (MVNP) after the eruption of the Mount Merapi volcano in 2010, was studied to i) identify the causal organism of the disease, ii) analyze the disease symptoms, iii) understand the spatio-temporal distribution of gummosis in the tree population and iv) examine how the disease affects the anatomy of tree wood. Pathological, morphological and molecular assessments were used in this study. Ceratocystis fimbriata was found associated with gummosis in the affected trees. The disease spread was probably aided by an ambrosia beetle, Euwallacea sp., which bores holes in the stem. The number of parenchyma cells in infected stems was significantly higher than in healthy stems, which apparently facilitated water and nutrition transport within trees, helping them to grow normally despite serious gummosis. The disease is noted to spread from the base of the trees, where the ambrosia beetle bores holes first, to the upper part. The management of invasion by A. decurrens in the MVNP area poses a serious challenge due its success as an invader in the volcano-impacted area and the threat of the gummosis pathogen spreading to other species, both of which will affect the regeneration and establishment of native species and recovery of the ecosystem.