Mulberry powdery mildew

The fungus is host-specific, primarily targeting mulberry trees (Morus spp.), completing its life cycle by infecting leaf tissues.

It survives the winter as cleistothecia, small dark fruiting bodies that develop on decaying leaves and bark, serving as a primary source of inoculum for the next season.

The mycelium grows on the surface of the leaves, sending haustoria into the host cells to absorb nutrients necessary for the fungus's growth and reproduction.

Dispersal occurs via airborne conidia, which are produced in large numbers and can spread the infection across entire orchards during favorable weather conditions.

The first clinical signs of the disease are small, white powdery patches on the abaxial (underside) surface of the mulberry leaves.

As the infection progresses, these patches expand and become more distinct, eventually covering larger areas of the leaf surface with a fungal mat.

Developing cleistothecia appear as minute black specks embedded within the white mycelial growth, indicating the maturation of the fungus.

Affected leaves may show signs of yellowing, chlorosis, and upward curling, which significantly reduces the tree's overall vigor.

In severe cases, the powdery coating may spread to the young, tender shoots and leaf petioles, leading to stunted growth and distortion.

Powdery mildew development is most rapid in warm, humid environments where the temperature ranges between 20°C and 28°C.

Limited air circulation in dense tree canopies creates a microclimate with stagnant, humid air that is ideal for the germination of fungal spores.

Frequent fog or heavy dew during the nights provides sufficient surface moisture for the initial stages of infection without washing away the mycelium.

Shaded areas or locations with poor light exposure significantly increase the susceptibility of the mulberry trees to this specific pathogen.

Low levels of soil moisture followed by rapid increases in humidity can often trigger an outbreak of the disease during the mid-summer season.

The primary damage is caused by the loss of photosynthetic area, as the mycelial mat blocks sunlight from reaching the leaf tissue.

Premature leaf drop reduces the tree's ability to store energy, making it more vulnerable to winter frost and decreasing growth in the following year.

For mulberry producers, the disease drastically reduces the yield and quality of leaf fodder for silkworm rearing, causing significant economic losses.

Long-term infestation leads to the weakening of the tree's structure and can make it more prone to secondary wood-rotting fungal infections.

The aesthetic value of the trees is also compromised, which is particularly relevant in urban landscapes and parks where mulberry trees are planted for shade.

Effective management begins with strict sanitation, including the collection and destruction of all fallen leaves to remove the overwintering inoculum.

Proper pruning practices that open the canopy to sunlight and facilitate better air movement are essential for preventing the buildup of humidity.

Chemical control involving sulfur-based fungicides or systemic chemical agents can be applied as a preventive measure when conditions are favorable for disease spread.

• Regular sanitation of the orchard floor.
• Systematic pruning to improve canopy airflow.
• Maintaining healthy soil fertility to boost tree resistance.
• Timely fungicide applications during high-risk periods.

Selecting resistant cultivars is the most sustainable approach for long-term management, especially in regions with historically high disease pressure.