Gummosis of apricot

Gummosis is a serious physiological condition affecting stone fruit trees, including the apricot (Prunus armeniaca), characterized by the secretion of a viscous, amber-colored sap known as gum. While it is not a primary pathogen itself, it is a clinical sign of underlying stress, fungal infection, or bacterial disease.

The primary causes of gummosis often involve biotic factors such as fungal infections (moniliosis or shot-hole disease) or bacterial canker. Additionally, physical damage to the bark caused by pruning, insects, or environmental stress—such as severe frost damage or sunburn—can trigger the tree to exude sap as a defense mechanism.

The most visible symptom is the accumulation of hardened, glassy gum deposits on the bark of trunks and branches. Over time, the affected areas become prone to deep cracks and cankers, which physically disrupt the transport of water and nutrients, eventually leading to branch dieback or total tree decline if left unmanaged.

Conditions that favor the development of gummosis include poorly drained soils, imbalanced fertilization (excessive nitrogen), and rapid temperature fluctuations. When the tree is under physiological stress, its natural defense systems are compromised, making it susceptible to the colonization of pathogens that perpetuate the cycle of gum production.

Management and prevention focus on eliminating the source of stress. Key steps include:

• Pruning and destroying infected branches to limit pathogen spread.
• Cleaning out cankers down to healthy tissue and applying disinfectant pastes.
• Maintaining proper soil moisture and balanced nutrient application.
• Protecting the bark from physical injury and applying trunk washes during dormant seasons.