Angular leaf spot of grapevine

The life cycle of this pathogen involves both sexual and asexual stages. The fungus overwinters as pseudothecia within infected leaf litter. When environmental conditions improve in the spring, ascospores are released and dispersed by wind and rain, starting the infection cycle.

Under warm and humid conditions, the pathogen undergoes rapid asexual reproduction, producing conidia on the underside of the leaves. These spores facilitate secondary infections, allowing the disease to spread quickly across the vineyard during the growing season.

High relative humidity and frequent rain events are crucial for the development of the disease. Water films on the leaf surface are necessary for the spores to germinate and penetrate the host tissue, leading to the formation of characteristic lesions.

The economic impact of the disease is significant, as it leads to premature defoliation. This reduction in the leaf surface area hampers the accumulation of sugars and starch, weakening the vine's vigor and reducing its ability to survive harsh winter temperatures.

The primary hosts for this pathogen are grapevine species. The disease specifically targets the leaves, causing tissue death within the leaf vein boundaries, which compromises the plant's overall metabolic functions and development.

Symptoms appear as distinct, angular spots on the foliage. These lesions are bounded by the small veins of the leaf, giving them a sharp, geometric appearance. The color of the spots typically ranges from brown to reddish-brown.

On the underside of the leaves, a dark or olive-grey moldy growth may be visible, which consists of the fungus's conidia. As the infection progresses, these spots may merge, causing extensive necrosis and eventual shedding of the leaves.

Sanitation is the cornerstone of managing Mycosphaerella angulata. Removing and destroying fallen leaves prevents the fungus from overwintering and reduces the inoculum source for the following season.

Cultivation practices that improve canopy airflow are essential. Regular pruning, thinning, and proper training of the vines help keep the foliage dry, which significantly inhibits the germination of fungal spores and the spread of the pathogen.

Fungicide applications are recommended in areas with high disease pressure. Copper-based compounds are commonly used for preventative measures, while systemic fungicides such as triazoles are effective for therapeutic control when symptoms are first spotted.