Pleurophoma disease

Early symptoms include chlorotic spots on leaves that eventually turn into necrotic lesions with brown or dark grey centers.

On stems and branches, the disease manifests as sunken lesions that can develop into girdling cankers, disrupting plant circulation.

A diagnostic sign is the appearance of tiny black dots on the surface of necrotic areas, which are the fungal pycnidia breaking through the epidermis.

Heavy infection leads to premature defoliation and stunted plant growth, significantly reducing the vigor of the affected crops.

High humidity promotes the emergence of a spore-bearing layer on the surface of lesions, serving as secondary inoculum for further spread.

The disease is caused by the imperfect fungus Pleurophoma pleurospora, which belongs to the Sphaeropsidales order. The pathogen is known for its high persistence in soil and debris.

The fungal mycelium invades plant tissues, interfering with the vascular system and nutrient transport. It produces pycnidia, which are small fruiting bodies containing spores that spread the infection.

The biological cycle of the fungus is strictly dependent on moisture availability. Rain splash is the primary mechanism for dispersing spores to healthy plants nearby.

The pathogen affects a variety of agricultural crops, often targeting tissues that have been weakened by environmental stress or poor management.

Under favorable conditions, the fungus remains active throughout the growing season, posing a continuous threat if left unchecked.

The development of Pleurophoma pleurospora is favored by high humidity (over 70-80%) and moderate temperature ranges.

Prolonged rainfall events during the growing season facilitate the mass production and splash-dispersal of infectious pycnospores.

Poor agricultural practices, such as high planting density and inadequate weed control, increase the humidity within the crop canopy.

Nutrient deficiencies, particularly regarding trace elements, weaken the plant's immune system, making it more susceptible to infection.

Accumulation of infected plant debris in the field is the primary factor for the carry-over of the pathogen into subsequent seasons.

The primary damage results from a reduction in the photosynthetic area, which leads to diminished carbohydrate production and yield loss.

Infection of the stem can result in structural failure, causing plants to break or lodge, especially during windy conditions.

Quality and marketability of produce are compromised by the disease, leading to substantial economic losses for farmers.

Severe infestations can lead to complete crop failure if conditions remain wet and conducive to disease spread for an extended period.

Infected crops are also more prone to secondary colonization by opportunistic pests, further exacerbating the damage.

Crop rotation is the most effective cultural practice to break the pathogen's life cycle and reduce inoculum levels in the soil.

Thorough cleanup and deep tillage of crop residues are essential to remove the primary sources of the fungus.

Fungicide applications, specifically copper-based or systemic products, are recommended when early symptoms are detected to prevent widespread infection.

The use of disease-resistant varieties and certified healthy planting material is a cornerstone of effective disease management.

Maintaining proper plant spacing and ensuring good airflow within the crop canopy are crucial for limiting the microclimate conditions that favor the fungus.