Trichoderma citrinum

Trichoderma citrinum is a fungal species that, while often studied for its potential in biocontrol, can also function as a pathogen in specific agricultural contexts. Under conditions of plant stress or high moisture, this organism acts as an agent of decay, attacking both the woody structures of perennial plants and the root systems of various crops.

The disease primarily manifests as soft rot or wood decay. The fungus utilizes its complex enzyme system to degrade structural polysaccharides such as cellulose and lignin. By entering through wounds, pruning cuts, or weakened vascular tissues, it gradually dismantles the structural integrity of the plant, leading to systemic weakness.

The host range is broad, significantly impacting orchard trees, ornamental shrubs, and nursery seedlings. Plants weakened by frost, insect damage, or environmental stressors are significantly more susceptible to colonization. In greenhouse environments, the presence of this fungus is often linked to poor drainage and high humidity levels.

Symptoms of infection are distinct, often identified by the presence of a characteristic yellowish-green fungal colony or mycelial mat on the affected tissue surface. The underlying plant tissue becomes soft, discolored, and emits a musty odor as the degradation process progresses deeper into the xylem or root core.

Strategic prevention and control measures include:

• Strict sanitation during pruning by disinfecting tools with alcohol or bleach.
• Applying protective wound sealants to any exposed wood surface.
• Improving soil drainage to prevent stagnant water near the root collar.
• Monitoring irrigation systems to ensure humidity remains at balanced levels.
• Removing and destroying infected plant debris to reduce the inoculum load.