Citrus gummosis

These pathogens thrive in moist soil environments and are capable of attacking the root system and the lower trunk, disrupting the plant's vascular integrity.

The fungus produces motile zoospores that can swim through saturated soil or water films to reach the susceptible tissues of the tree's bark or roots.

The disease can persist in the soil for extended periods as resilient oospores, which allow the pathogen to survive harsh conditions and reinfect healthy trees later.

The biology of the pathogen is closely tied to moisture levels, making water management the most critical factor in controlling its life cycle within the orchard.

The hallmark symptom is the appearance of amber-colored gum exudation from cracks in the bark of the trunk, typically near the soil line.

The affected bark becomes discolored, necrotic, and eventually cracks or peels off, revealing underlying wood that often shows signs of reddish-brown decay.

Foliage symptoms include yellowing (chlorosis), leaf drop, and dieback of branches, reflecting the tree's inability to transport water and nutrients properly.

In advanced stages, the tree may show stunted growth and a general decline in vigor, with fruit production becoming severely compromised or stopping entirely.

• Amber resinous exudates on the lower trunk.
• Cracked and necrotic bark near the crown.
• Internal wood discoloration and decay.
• Leaf chlorosis and canopy thinning.

The primary driver of gummosis is excessive soil moisture and poor drainage, which creates an anaerobic environment favorable for Phytophthora activity.

Deep planting of saplings, where the graft union or root collar is buried in soil, significantly increases the risk of the pathogen infecting the trunk.

High relative humidity and warm temperatures (20–25°C) facilitate the rapid dispersal of spores and the development of the disease across the orchard.

Physical injuries to the bark caused by heavy machinery, weed trimmers, or improper pruning provide direct entry points for the fungus to colonize the tree.

Using contaminated tools or introducing infected nursery stock are common ways the disease is spread into previously clean sections of an orchard.

Citrus gummosis is a destructive disease that, if left untreated, leads to the girdling of the tree trunk and inevitable death of the infected specimen.

The destruction of the vascular system starves the tree, rendering it susceptible to secondary infestations by beetles and opportunistic decay-causing fungi.

Economic impact is significant, as growers face the loss of productive trees, increased expenditures on fungicide applications, and lower overall fruit yield.

The pathogen spreads easily through runoff water and contaminated equipment, making it difficult to contain without strict sanitation protocols in place.

Damage to the root system is often irreversible, meaning that even if the tree survives, it may never regain its original level of productivity and vigor.

Prevention begins with ensuring excellent orchard drainage and planting trees at the correct depth, ensuring the root crown remains dry and aerated.

Infected areas should be surgically scraped back to healthy, green tissue and treated with copper-based fungicides to inhibit further fungal growth.

Systemic fungicides, particularly those containing fosetyl-aluminum or metalaxyl, are effective in controlling the pathogen by boosting the tree's systemic defenses.

Strict sanitation practices, including the regular disinfection of pruning tools with alcohol or bleach, are essential to prevent the mechanical spread of the fungus.

Orchard management should focus on avoiding injuries to the trunk, maintaining balanced fertilization, and monitoring for early signs of bark discoloration.