Endemic and Emerging Pathogens Threatening Cork Oak Trees: Management Options for Conserving a Unique Forest Ecosystem

Abstract

Cork oak (Quercus suber) forests are economically and culturally intertwined with the inhabitants of the Mediterranean basin and characterize its rural landscape. These forests cover over two million hectares in the western Mediterranean basin and sustain a rich biodiversity of endemisms as well as representing an important source of income derived from cork production. Currently cork oak forests are threatened by several factors including human-mediated disturbances such as poor or inappropriate management practices, adverse environmental conditions (irregular water regime with prolonged drought periods), and attacks of pathogens and pests. All these adverse factors can interact, causing a complex disease commonly known as “oak decline.” Despite the numerous investigations carried out so far, decline continues to be the main pathological problem of cork oak forests because of its complex etiology and the resulting difficulties in defining suitable control strategies. An overview of the literature indicates that several pathogenic fungi and oomycota can play a primary role in the etiology of this syndrome. Therefore, the aim of this review is to analyze the recent advances achieved regarding the bio-ecology of the endemic and emerging pathogens that threaten cork oak trees with particular emphasis on the species more directly involved in oak decline. Moreover, the effect of climate change on the host-pathogen interactions, a task fundamental for making useful decisions and managing cork oak forests properly, is considered.

Fungal community in olive fruits of cultivars with different susceptibilities to anthracnose and selection of isolates to be used as biocontrol agents

“…(Xiong et al, 2013). The most abundant epiphytes were C. cucumerinum and B. mediterranea, both plant-pathogens that cause scab of cucurbits on cucumbers (Kwon et al, 1999) and charcoal canker in particular on the genus Quercus (Moricca et al, 2016), respectively.…”

Site‐specific distribution of oak rhizosphere‐associated oomycetes revealed by cytochrome c oxidase subunit II metabarcoding

“…Iberian oak decline is characterized by a reduction of fine root density accompanied by root lesions leading to wilting and discoloration of leaves and ultimately to a reduction in canopy density (Corcobado, Cubera, Moreno, & Solla, ; de Sampaio e Paiva Camilo‐Alves, Clara, & Almeida Ribeiro, ). In addition to abiotic factors such as water stress, oak pathogens such as Phytophthora cinnamomi are thought to predispose the trees to decline (Brasier, ; Brasier, Robredo, & Ferraz, ; Corcobado, Cubera, et al, ; Moricca et al, ; de Sampaio e Paiva Camilo‐Alves et al, ). However, interactions between evergreen oaks and pathogens appear more complex.…”

Dispersal and Propagule Pressure of Botryosphaeriaceae Species in a Declining Oak Stand is Affected by Insect Vectors

“…Here, the repeated occurrence of heat extremes, accompanied by a decrease in precipitation and thus prolonged summer drought, has caused substantial heat and water stress to tree vegetation, resulting in their physiological impairment, stunted growth, dieback and, in some instances, mortality [6]. Climate-driven changes, besides having exacerbated the vulnerability of the trees, have also modified the dynamics of forest insects and pathogens, dramatically increasing the likelihood of attacks by these damaging agents [7,8].…”