Dichotomophthoropsis

The fungus acts as a parasite, affecting primarily the aerial parts of plants. Its life cycle includes active sporulation phases, which allows it to spread rapidly across fields when leaf surface moisture is present.

The fungal mycelium penetrates plant tissues through stomata or mechanical damage to the epidermis. Within the tissues, it develops intercellularly, gradually destroying cell structures and causing necrotic processes.

The pathogen survives between seasons in the form of chlamydospores or sclerotial structures found on plant debris. This makes the fungus extremely resistant to unfavorable environmental factors.

The fungus shows high adaptability to various temperature regimes, which ensures its survival in the soil and on stubble for several years until a susceptible host appears.

The primary sign of infection is the appearance of small, chlorotic spots that gradually grow and become necrotic. The color of the spots varies from light brown to dark brown depending on the stage of fungal development.

A faint fungal bloom, consisting of conidia and conidiophores, can often be seen on the surface of necrotic zones. Under high humidity, the bloom becomes denser and takes on an olive or gray hue.

Eventually, the spots merge, affecting a significant part of the leaf blade, which leads to premature drying of the leaves. The infection may spread to stems and petioles, causing deformation and subsequent necrosis.

A characteristic feature of the lesion is the presence of a distinct margin around the necrotic spots, separating healthy tissue from dying tissue. The center of the spot often cracks or falls out, creating a shot-hole appearance.

When generative organs are affected, flower wilting or partial sterility of inflorescences is observed. This results in underdeveloped fruits and a significant decrease in the commercial quality of the harvest.

The development of Dichotomophthoropsis is promoted by high relative humidity, exceeding 75-80 percent. Frequent rainfall and fog are key factors that trigger disease outbreaks in fields.

The optimal temperature range for spore germination and active mycelial growth is between +20 and +25 degrees Celsius. However, the pathogen maintains activity at lower temperatures if high humidity is present.

Densely planted crops, where air ventilation is restricted, create a favorable microclimate for the accumulation of inoculum. Moisture stagnation in the lower parts of stems significantly accelerates the infection process.

The presence of free moisture (dew or condensate) on the plant surface is a critical requirement for conidia germination. Even short periods of wetting can initiate the infection process.

Plants weakened by adverse weather conditions, pest attacks, or nutrient deficiencies are infected by the fungus much faster and more severely than healthy individuals.

The harmfulness of the disease lies in a significant reduction of the assimilating surface area of the leaves. This disrupts photosynthetic processes and leads to general suppression of plant growth and development.

In cases of severe infection, premature leaf fall occurs, which minimizes biomass accumulation. As a result, seed filling or fruit formation slows down, directly impacting the final yield.

The destruction of tissues by the fungus creates entry points for secondary bacterial and fungal infections. The combined impact of several pathogens can lead to the death of a significant part of the crop in a short time.

The quality of the produced crop decreases sharply: seeds lose their sowing properties, and horticultural products lose their marketability. This leads to significant economic losses for agricultural producers.

In cases of massive spread, total loss of the harvest is possible in specific areas. Timely detection of infection foci is critical to prevent epiphytotic spread of the disease.

Effective management of Dichotomophthoropsis is based on strict adherence to crop rotation, excluding susceptible crops from rotation for 3-4 years. This interrupts the pathogen's life cycle and reduces the infection pressure in the soil.

An important step is deep plowing to incorporate plant debris into the soil immediately after harvest. This promotes rapid decomposition and death of the mycelium and fungal spores.

The use of high-quality seed material and seed treatment with systemic fungicides is recommended. This protects seedlings from early infection and strengthens the plant's immunity.

Applying fungicides during the growing season at the first signs of the disease helps stop the spread of the fungus. Preparations from the triazole and strobilurin groups demonstrate the highest efficacy.

• Maintaining optimal seeding rates to prevent overcrowding.
• Balanced application of fertilizers, especially potassium to strengthen cell walls.
• Regular phytosanitary monitoring of crop conditions.
• Destruction of weeds that act as infection reservoirs.