Pluripassalorosis

The primary sign of the disease is the appearance of chlorotic spots on the leaves, which gradually increase in size. As the pathology progresses, the color of the spots changes to brown or dark brown.

In the center of the affected areas, especially on the underside of the leaf, a grayish or olive-colored layer forms. This is an accumulation of conidia and conidiophores, indicating the active stage of fungal sporulation.

In cases of severe disease development, the spots may merge, covering significant areas of the leaf blade. This leads to premature yellowing and subsequent drying of the leaves.

A characteristic symptom is also the deformation of young leaves and stunted growth of the plants. In some cases, the infection may spread to stems and petioles, causing necrosis.

Failure to respond promptly to the appearance of primary infection foci leads to the spread of the disease across a significant portion of the plant's vegetative mass in a short time.

The causal agent of this disease is a microscopic imperfect fungus belonging to the genus Pluripassalora. This pathogen specializes in infecting the vegetative parts of plants, primarily the leaf apparatus.

Taxonomically, this fungus belongs to the group of mycelial pathogens capable of forming specific conidiophores that emerge through the leaf stomata. The life cycle of the pathogen is closely linked to the presence of free moisture on the plant surface.

The infection spreads through conidia, which are dispersed by wind, rain splashes, or during agricultural activities. The pathogen can survive in the soil or on crop residues in the form of dormant structures.

The biological characteristics of Pluripassalora include the ability to rapidly accumulate infectious potential under favorable environmental conditions. The pathogen exhibits high virulence against susceptible plant species.

Identification of the pathogen in laboratory settings requires microscopic analysis of the affected tissues to detect the characteristic sporulating structures of the fungus.

The development of Pluripassalorosis epiphytotics is favored by high air humidity conditions, exceeding 80–85 percent. The optimal temperature range for mycelial growth varies from 20 to 25 degrees Celsius.

The presence of free moisture from heavy dew, fog, or improper overhead irrigation is a critical factor for spore germination. Stagnant air in crops significantly accelerates the spread of infection.

Dense plantings, which create a specific microclimate with slowed moisture evaporation, are particularly susceptible to the disease. Poor aeration within the plant canopy exacerbates the situation.

Periods of prolonged rain combined with moderately warm weather create an ideal background for mass reproduction of the pathogen. During such periods, the incubation period of the pathogen is shortened to a few days.

Failure to follow crop rotation and leaving unharvested crop residues in the field creates conditions for the survival and accumulation of infectious potential in the agroecosystem.

The main danger of the disease lies in the sharp reduction of the leaf assimilation surface area, which leads to the disruption of photosynthesis. This directly impacts crop productivity and biomass accumulation.

Premature leaf drop causes stress in plants, which negatively affects the development of reproductive organs. As a result, the quantity and quality of the harvest are significantly reduced.

Infection of weakened plants by fungal pathogens often creates entry points for secondary bacterial and fungal pathogens. This can lead to a complete loss of product marketability.

Under production conditions, the development of the disease in fields leads to substantial economic losses, requiring additional expenses for expensive fungicide treatments.

• Reduced quality of seed material when seed crops are affected.
• Decreased shelf life of fruits and vegetables during storage.
• Risk of total crop failure for sensitive varieties during wet summers.

The basis of control is the observance of proper crop rotation with spatial isolation of crops. It is important to exclude monoculture, which contributes to the accumulation of specific pathogens in the soil.

Thorough incorporation or destruction of crop residues is a mandatory preventive measure. This destroys the biological habitat in which the pathogen survives between seasons.

Using resistant varieties and hybrids remains the most cost-effective method of control. Timely selection of seed material with high phytosanitary purity significantly reduces risks.

The use of preventive fungicides allows for the suppression of primary infection foci. Treatments should be carried out at the first signs of symptoms or when weather conditions favorable for the fungus occur.

Agricultural practices aimed at improving crop ventilation (optimal density, timely thinning, and weeding) significantly reduce microclimate humidity and inhibit disease development.