Microsphaera euphorbiae

Biologically, this organism is an ascomycete fungus that forms a characteristic mycelial coating on the surface of affected plant organs. A key feature is the formation of cleistothecia — fruit bodies essential for the fungus to overwinter under adverse conditions.

The life cycle includes an asexual stage (conidial), which ensures rapid spread of infection during the growing season, and a sexual stage that culminates in the formation of spores within specialized structures.

The pathogen spreads primarily via airborne transmission: microscopic conidia are easily carried by the wind over long distances, infecting healthy plant tissues or neighboring plants.

Microsphaera species show high adaptive capacity, making them persistent parasites that require constant monitoring of spurge plantations in both greenhouses and open fields.

The primary targets for this fungus are various species of the genus Euphorbia (spurge). The pathogen actively colonizes leaves, stems, and, in severe cases, flower stalks, extracting vital nutrients from the host.

Harmfulness manifests through the inhibition of photosynthesis due to stomatal closure and epidermal layer damage, leading to premature leaf drop and the degradation of the plant's decorative or medicinal value.

Severe infestations often result in metabolic disruption, causing the plant to stop growing, shed buds, and become highly susceptible to other secondary pathogens and pests.

This pathogen is particularly dangerous for young seedlings and weakened plants, where fungal infection can lead to the complete death of the aerial part of the plant.

The economic impact involves the loss of marketability for ornamental spurges and a reduction in the yield of medicinal raw materials, causing direct financial losses for nurseries.

The first and most noticeable symptom is the appearance of a loose, white, powdery coating on either the top or bottom of the leaf blade, which eventually thickens over time.

As the mycelium matures, tiny dark dots — cleistothecia — become visible on the surface of affected areas, changing color from yellowish to dark brown or black as they develop.

The leaves of infected plants begin to curl, turn yellow, and take on an unhealthy appearance, often deforming while still in the stage of active growth.

When stems are affected, necrotic spots form, which can eventually merge, causing the entire shoot to twist or wither.

Eventually, the affected tissues lose their turgidity and become brittle, while the plant takes on a depressed, "dusty" appearance characteristic of powdery mildew infections.

Agrotechnical control includes the mandatory removal and destruction of plant debris where the fungus overwintering bodies (cleistothecia) reside, as well as maintaining optimal planting density to prevent moisture stagnation.

An effective preventive method involves the use of systemic fungicides containing triazoles, which penetrate plant tissues rapidly to halt the development of the mycelium.

In greenhouses, maintaining proper air humidity and ensuring regular ventilation are critical, as excessive moisture promotes the immediate germination of fungal spores.

To prevent the spread of infection, it is recommended to conduct preventive treatments with sulfur-based preparations at the beginning of the growing season, especially during years with high humidity.

• Regular inspection of plantings for the presence of white powdery patches.
• Prompt removal and disposal of infected leaves and shoots.
• Application of biological preparations based on antagonistic bacteria.
• Implementation of crop rotation and spatial isolation practices.