Witches' broom disease

Witches' broom disease is a devastating fungal infection caused by the pathogen Crinipellis perniciosa. It is recognized as one of the most significant threats to cocoa production globally, capable of causing massive crop failure by affecting both vegetative and reproductive growth of the host plant.

The primary host for this fungus is the cocoa tree (Theobroma cacao). The pathogen specifically targets growing points and developing fruits, leading to profound physiological changes in the plant's vascular and developmental systems, which eventually results in the characteristic deformation of the canopy.

The most distinctive symptom is the formation of dense clusters of thin, distorted, and adventitious shoots, known as «witches' brooms». Affected pods undergo internal decay, turning black and becoming inedible. Following periods of high humidity, the fungus produces small, pinkish, fan-shaped basidiocarps on the infected twigs and pods.

Development and spread are favored by high rainfall and high humidity levels. The spores (basidiospores) are released into the air and transmitted by wind or splashing rain to new, susceptible tissues. Once the spores germinate on a suitable host surface, they penetrate the plant tissues, leading to systemic infection.

Management strategies focus on integrated pest management practices. These include intensive sanitation, where all infected brooms and pods are removed and destroyed to reduce the inoculum pressure. Additionally, breeding for resistance and maintaining optimal canopy structure are critical to reducing microclimate conditions that favor infection.

• Rigorous removal of infected tissues
• Sanitation of cocoa plantations
• Breeding and planting resistant cacao varieties
• Improving air circulation in the canopy