Pseudopezicula leaf scorch

Pseudopezicula leaf scorch, also known as the red fire of grapes or "brenner" in some regions, is caused by the fungus Pseudopezicula tracheiphila. This pathogen is a significant threat in viticulture, as it disrupts the vascular system of grapevines, preventing the transport of essential nutrients and water.

The primary host for this fungus is the cultivated grapevine (Vitis vinifera). The infection specifically targets the leaf tissue, though in severe cases, it can affect leaf stalks and pedicels, directly impacting the vine's ability to support fruit development.

Symptoms are distinct and evolve through the season. Initially, chlorotic spots appear between the veins of the leaves. As the disease progresses, these spots develop a reddish or reddish-brown coloration with a dark margin. Eventually, the affected tissue undergoes necrosis, leading to early defoliation and a weakened vine state.

The development and spread of Pseudopezicula are highly dependent on environmental factors. The fungus thrives in cool, wet conditions during the spring. Rain droplets facilitate the spread of ascospores from overwintering infected leaf litter onto new leaf growth, initiating the primary infection cycle.

The economic impact of this disease includes reduced grape quality, lower sugar accumulation, and poor vine winter hardiness due to premature leaf drop. Effective management relies on integrated strategies:

• Removing and destroying infected leaves to reduce the primary inoculum load.
• Applying preventative fungicide sprays timed with the emergence of susceptible tissue.
• Improving canopy management to ensure air circulation and reduce humidity around leaves.