Rose Dieback Disease Management: Symptoms, Treatment, Chemical, Biological, and Organic Control

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.

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Percentage of Yield Loss Due to Rose Dieback Disease in Rose Crop

The disease can cause 30% yield losses in the United States. In Mexico, yield losses are 25%. In India, the yield losses are 40%. In Bangladesh, the losses are 50%. In Sri Lanka, the losses are 35%. In China, a 60% yield loss is seen. In Africa, yield losses are up to 40%.
In Indonesia, it is 30%. In Vietnam, it is 10%. In Ecuador, it is 20%. In Peru, it is 5-10%. In the Philippines, it is 25%. In Malaysia, it is 30%. In Colombia, it is 40%. In Thailand, it is 20%. In Brazil, it is 50%. In Australia, the losses are 30%. The Economic Threshold Level is determined at around 15-20% of the affected crop.

Rose Dieback Disease Management by Cultural Control

Spacing – Proper spacing helps reduce humidity levels and allows better penetration of sunlight, which can help dry out the foliage and inhibit fungal growth.
Sanitation – Remove and destroy infected plant material, including pruned canes, dead branches, and fallen leaves.
Pruning – Prune roses during the dormant season or when the disease is not actively spreading to minimize the risk of infection.
Soil Management – Ensure the soil is well-drained to prevent waterlogging and has good organic matter content.
Irrigation Management – Avoid excessive overhead irrigation that can lead to prolonged leaf wetness.

Rose Dieback Disease Management by Biological Control

Fungal Antagonists – Trichoderma harzianum and Trichoderma viride colonize the rhizosphere, inhibit its growth, and induce plant defense mechanisms.
Bacterial Agents – Bacillus subtilis, Pseudomonas fluorescens, and Streptomyces spp. suppress the growth of the pathogen, acting as a protective barrier around the roots and foliage.

Rose Dieback Disease Management by Chemical Control

Spray Carbendazim, Mancozeb, Chlorothalonil, Difolatan, COC, Cyprodinil, Azoxystrobin, Propiconazole, or Tebuconazole to control the fungus spread.
Fungicide Paste Application – Apply the Chaubatia paste on the pruned parts of the plant.

Rose Dieback Disease Management by Organic Control

Spray Copper-based fungicides, such as copper sulfate or copper hydroxide, to protect the plant surfaces and prevent infection.
Spray Sulphur-based fungicides, such as elemental sulfur and sulfur dioxide, to control the disease.
Compost teas are liquid extracts made from compost or vermicompost and are rich in beneficial microorganisms.
Plant extracts from neem, ginger, garlic, and turmeric leaves, such as powders, oils, and cakes, are used as a preventive measure to control the disease.
Essential oils like tea tree, thyme, oregano, clove, and cinnamon can also control the disease.

Rose Dieback Disease Management by Preventive Control Measures

Use organic mulch around the plant’s base, like straw or wood chips, to suppress weed growth, maintain soil moisture, and regulate soil temperature.
Avoid crowded plantings that promote high humidity and reduce air movement.
Proper plant spacing can help to increase air circulation and sunlight penetration to reduce the disease incidence and severity.
Use disease-free, healthy, and certified planting material only.
Always use sterilized and disinfected pruning equipment to prevent the spread of the disease to new trees.
Regularly monitoring the crops for signs of disease will help to find and manage the disease early before it spreads.

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Conclusion

The Rose Dieback Disease caused by Diplodia rosarum is a significant threat to Rose production worldwide. It can lead to substantial yield losses and impact the economic state of rose farmers. Integrated disease management combines various control measures to create a comprehensive and sustainable approach to disease control.

Rose Dieback Disease Management: Symptoms, Treatment, Chemical, Biological, and Organic Control

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