The Silent Killer: A Review Unfolding the Mystery of Fungal Pathogens Causing Canker Diseases in Tree Crops

Abstract

Canker diseases caused by fungal pathogens pose a formidable threat to global forest ecosystems and commercial tree crops, often resulting in extensive economic and ecological losses. Major fungal genera associated with canker development include: Phytophthora, Hypoxylon, Chrysoporthe, Cytospora, Fusarium, Seiridium, Botryosphaeria, Phomopsis, Ceratocystis, Cryptodiaporthe, Gremmeniella, Nectria, Sirococcus clavigignenti juglandacearum, Lasiodiplodia and Sphaeropsis. The interplay between host susceptibility, climate change and fungal virulence factors emerges as a central theme influencing canker outbreaks across diverse agroecological zones. Each pathogen is examined through the lens of its characteristic symptoms, from classic sunken, girdling cankers to unique features like gummosis, dieback, fruit blemishes and vascular discoloration. Early diagnosis of plant diseases is critical for timely and appropriate management, especially in high-density orchards where pathogens can spread rapidly. Accurate identification and characterization are crucial for increasing knowledge about these pathogens and developing effective management strategies. Despite extensive reports, information on pathogen diversity, host interactions, and disease progression remains fragmented. By mapping the fungal diversity involved in canker development, this review underscores the urgent need for proactive, cross-disciplinary approaches to safeguard forest and orchard health in the face of phytopathological threats.