Lachnocladium brasiliense

The most visible sign of the disease is the development of a distinct, velvety, pinkish or white crust-like layer on the branches and main trunks of the host plant. This growth is a dense mass of mycelial development.

As the fungal growth persists, the underlying bark begins to crack and peel away. Deep necrotic lesions, or cankers, are often found in the areas where the fungal layer is thickest, indicating damage to the cambium.

Affected plants often show systemic symptoms, including chlorosis of the foliage and premature leaf drop. These symptoms are caused by the disruption of water and nutrient transport due to the damage to the conductive vessels.

• Velvety pink or white mycelial mats on the bark.
• Progressive dieback of distal branches.
• Canker formation and longitudinal bark splitting.
• Premature senescence and defoliation of the canopy.
• Stunted growth and reduced overall vigor of the host plant.

Under conditions of high humidity, the fungal layer may produce reproductive structures that appear as small, bumpy outgrowths. These structures are the primary source of airborne spores that infect surrounding healthy plants.

The disease is caused by the fungus Lachnocladium brasiliense, a member of the Basidiomycota phylum. This pathogen is known for infecting woody stems and branches in various tropical and subtropical crops.

The fungus develops a resilient mycelium that colonizes the cortical tissues. During its life cycle, it produces basidiospores that are effectively disseminated by wind and rain splashes, leading to rapid disease spread within a plantation.

Biologically, Lachnocladium brasiliense acts as a necrotrophic pathogen. It secretes specialized enzymes to degrade plant cell walls, which allows the fungus to extract nutrients and expand its colony deeper into the host's vascular tissues.

The survival of the fungus is largely dependent on the presence of crop debris. If infected wood is left in the orchard, the fungus can maintain its viability for long periods, providing a continuous source of inoculum for the next season.

Modern laboratory diagnostics use PCR-based methods to identify Lachnocladium brasiliense, as morphological identification alone can be difficult due to the slow growth rate of the fungus in pure culture media.

The spread of Lachnocladium brasiliense is heavily favored by prolonged periods of high relative humidity and moderate temperatures. The fungus thrives when moisture remains on the canopy for extended durations.

Optimal development usually occurs in warm environments between 20°C and 25°C. In such climates, the fungus can colonize new tissues quickly, especially if the host plant is under stress or has existing wounds.

Poor canopy management, leading to dense vegetation, is a significant risk factor. Lack of airflow prevents the rapid evaporation of water, creating a micro-environment that promotes spore germination and infection.

Physical injuries, whether from pruning tools, hail damage, or insect activity, serve as primary entry points for the pathogen. Once the bark integrity is breached, the fungus finds it much easier to penetrate the interior tissues.

Seasonal patterns, particularly rainy seasons, are critical for the spread of this disease. Rain splash is the main mechanism for transferring spores from infected canopy levels to lower, previously healthy branches.

The damage caused by Lachnocladium brasiliense can be severe, potentially leading to the death of entire branches or the complete loss of a tree. This results in significant yield reduction and increased maintenance costs.

The disruption of the vascular system prevents nutrients from reaching developing fruits. This causes fruit drop, deformation, or quality degradation, making the yield economically unviable for commercial sale.

Chronic infection weakens the plant's structural integrity. Over time, trees become highly susceptible to secondary pathogens and physical breakage during strong winds, leading to long-term orchard decline.

In cases of widespread infection, an entire plantation can become non-productive. The cost of replacing dead trees and managing the spread makes this disease a serious threat to the financial stability of affected farms.

The pathogen's ability to remain in the field environment means that without rigorous sanitation, the disease pressure increases annually, making it increasingly harder to achieve effective control.

The primary control measure is the systematic pruning and removal of infected branches. It is crucial to cut well into the healthy wood—at least 10-15 cm below the infection site—to ensure no mycelium remains.

Application of copper-based fungicides serves as a prophylactic measure. Treating trees during the dormant season or before the onset of rainy weather can protect the bark from initial spore penetration.

Proper canopy management, including thinning to increase airflow and sunlight penetration, is essential. This reduces the time surfaces stay wet, which is a major deterrent to fungal development.

Strict disinfection of pruning tools is vital. Sterilizing equipment with alcohol or bleach solutions between trees prevents the accidental transfer of the fungus from symptomatic to healthy plants during seasonal maintenance.

Maintaining optimal tree vigor through balanced fertilization and correct irrigation helps the host plant build natural defenses. A healthy plant is significantly more resilient to fungal infections and recovers faster from stress.