The Rose Dieback Disease, caused by the fungal pathogen Diplodia rosarum, is one of the most common and destructive diseases affecting rose crops worldwide. The economic impact of Rose Dieback Disease is significant, as it attacks the woody tissues infecting the vascular system, 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 disease’s prevention and control are critical for rose production’s sustainability and profitability. 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 Dieback Disease in Rose crops, including its symptoms, identification techniques, and control.
Rose Dieback Disease Management
The Causal Organism of Rose Dieback Disease
- Diplodia rosarum is a fungus that belongs to the Family Botryosphaeriaceae of Order Botryosphaeriales of the Phylum Ascomycota.
- The spores, known as conidia, are hyaline (colorless), multicellular, and cylindrical.
- They are typically produced within small, black pycnidia, which are flask-shaped fruiting structures that contain the conidia.
- The pycnidia are often embedded in blackened lesions on infected stems or canes.
The Disease Cycle of Rose Dieback Disease
- The lifecycle of Diplodia rosarum begins when the conidia infect the plant through wounds or natural openings. Once on the plant surface, the spores germinate, producing hyphae that penetrate the plant’s outer layers. After penetration, the hyphae of Diplodia rosarum colonize and grow through the xylem, causing wilting and decline of the affected plant parts. The infected rose plants show characteristic lesions.
- Diplodia rosarum produces pycnidia, flask-shaped fruiting structures embedded within the infected plant tissues at a later stage of the disease cycle. The pycnidia contain spores called conidia, which are released into the environment, perpetuating the disease cycle.
Occurrence of Rose Dieback Disease in Rose Crop
- Location of Rose Dieback 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 Diplodia rosarum are Rose, Grapevine, Apple, Pear, Cherry, Peach, Walnut, Almond, Oak, Maple, Juniper, and Pine.
Favorable Conditions for Rose Dieback Disease Spread in the Field
- Temperature – The optimal temperature range for disease development is between 25-30°C.
- High Humidity – Spore germination and fungal growth are favored by high humidity.
- Overcrowding – Overcrowded planting and poor air circulation can contribute to increased humidity and limited airflow within the rose canopy.
- Leaf Wetness – Prolonged periods of leaf wetness, such as morning dew, rain, or overhead irrigation, favors the disease.
- Plant Stress – Plants under stress due to pruning cuts, wounds, injuries, and mechanical damage are more susceptible.
Damage Symptoms of Rose Dieback Disease
- The dieback disease is characterized by the progressive decline, wilting, and dieback of rose plants.
- The fungus primarily infects the woody tissues of rose plants, including stems, canes, and branches.
- Once the pathogen infects the vascular bundles, it obstructs water and nutrient flow and causes the characteristic symptoms of dieback.
- As the disease progresses, the affected branches may eventually die, leading to the overall decline and plant death.
- Other symptoms include wilting and discoloration of leaves, stunted growth, branch dieback from the tip downwards, and dark brown to black lesions on infected stems.
- These lesions often have a cracked or sunken appearance and may be accompanied by gumming or exudation.