The Rose Powdery Mildew Disease, caused by the fungal pathogen Sphaerotheca pannosa, is one of the most common and destructive diseases affecting rose crops worldwide. The economic impact of Rose Powdery Mildew Disease is significant, as it attacks the aerial parts, reduces flower yield, quality, and marketability, and can result in a substantial loss of yield. Effective disease management requires a combination of cultural, biological, and chemical control measures.
The prevention and control of the disease are critical for the sustainability and profitability of Rose production. To effectively manage this disease, it is important to understand its disease cycle, the mode of disease spread, and the best methods for controlling it. This article will provide an overview and discussion of the Rose Powdery Mildew Disease in Rose crops, including its symptoms, identification techniques, and control.
Rose Powdery Mildew Disease Management
The Causal Organism of Rose Powdery Mildew Disease
- Sphaerotheca pannosa is a fungus that belongs to the Family Erysiphaceae of Order Erysiphales of the Phylum Ascomycota.
- The mycelium of Sphaerotheca pannosa is septate, colorless, and develops numerous branching.
- The mycelium gives rise to specialized structures called conidiophores, which bear spores called conidia or ascospores. The conidia are oval to elongated in shape, non-motile, and unicellular.
- The conidiophores emerge from the mycelium and extend above the powdery mildew colonies.
- Cleistothecia, or chasmothecia, are spherical or irregular-shaped fruiting bodies produced by the fungus.
The Disease Cycle of Rose Powdery Mildew Disease
- During the winter, the fungus survives in dormant structures, such as mycelium or cleistothecia, on rose canes, fallen leaves, and plant debris.
- In spring, these structures release ascospores or conidia, which air currents carry to susceptible plant surfaces. These spores germinate and penetrate the plant tissues, initiating the infection process. The pathogen then develops mycelium on the plant surface, forming characteristic powdery mildew colonies.
Occurrence of Rose Powdery Mildew Disease in Rose Crop
- Location of Rose Powdery Mildew Disease: This disease occurs in Rose crops in India, Africa, China, Bangladesh, Sri Lanka, Vietnam, Thailand, Indonesia, Malaysia, the Philippines, the United States, Mexico, Brazil, Colombia, Ecuador, Peru, and Australia.
- Host Range: The most common crops affected by Sphaerotheca pannosa are Rose, Raspberry, Blackberry, Strawberry, Apple, Pear, Quince, and Almond.
Favorable Conditions for Rose Powdery Mildew Disease Spread in the Field
- Temperature – The optimal temperature range for the disease development is between 15-25°C.
- High Humidity & Shaded Conditions – The disease development is favored by shady conditions, with humidity of 40-100%.
- Leaf Wetness – Extended periods of leaf wetness, such as morning dew, rain, or overhead irrigation, favors the disease.
- Plant Stress – Plants under stress due to nutrient deficiencies, inadequate watering, or pest infestations are more susceptible.