Granulobasidium

Granulobasidium (specifically Granulobasidium vellereum) is a basidiomycetous fungus responsible for wood decay in various plant species. It acts as a necrotrophic pathogen, colonizing the bark and internal woody tissues of trees. While it may appear secondary in some ecosystems, in fruit orchards, it can cause severe damage to the structural integrity of branches, eventually leading to the death of affected tree limbs.

This pathogen primarily targets stone fruit trees, including cherries, plums, and apricots. It is particularly notorious for colonizing branch crotches and areas where the tree bark has been damaged by environmental factors or poor pruning techniques. Once established, the fungus can penetrate deeply into the xylem, disrupting the tree’s water-conducting systems and nutrient transport.

The visual symptoms of a Granulobasidium infection are characteristic of many white rot pathogens. Growers should monitor for:

• the formation of granular, whitish to cream-colored fruiting bodies;
• cracking and lifting of the bark tissue;
• necrosis in the wood underneath the infected area;
• foliage wilting on individual branches during the growing season.

Environmental conditions play a critical role in the development and spread of this disease. High humidity, mild temperatures, and poor air circulation within the orchard canopy are ideal for spore germination. The fungus spreads through basidiospores carried by wind or rain splash, making orchard sanitation and the protection of pruning wounds essential to preventing widespread outbreaks.

Effective management requires a proactive approach. Prevention starts with proper horticultural practices, such as clean cuts during pruning and immediate sealing of large wounds with appropriate dressings. Removing infected branches and ensuring optimal orchard airflow are crucial for reducing inoculum density. Fungicide applications, particularly those targeting wood-decay fungi during dormancy or immediately after pruning, can provide additional layers of protection for vulnerable trees.