Fighting Powdery Mildew In Roses: A Comprehensive Guide For Management And Control

Powdery mildew is one of the most common diseases that affect roses. Powdery mildew can cause significant damage to roses, reducing the quality and quantity of the flowers produced. In severe cases, the disease can lead to premature defoliation, reduced plant growth and even plant death. Powdery mildew thrives in cool, humid conditions with moderate temperatures between 16-24°C. High humidity levels and low light intensities also favour the development of the disease. This article will give complete information about causes, symptoms and management of powdery mildew in roses. 

Type of Infestation

• The primary infection occurs when the fungal spores are produced on infected leaves and are carried by wind or splashing water to healthy plants.
• Secondary infections occur when the fungal spores produce new infections on the same plant or on neighboring plants. The fungal fragments can survive for extended periods in infected plant debris.

Scientific Name: Sphaerotheca pannosa  

Most Affected States

Powdery mildew is a widespread disease that affects roses in all regions of India. However, some of the major affected states include Uttar Pradesh, Maharashtra, Karnataka, Tamil Nadu and West Bengal.  

Symptoms of Rose Powdery Mildew

The symptoms of powdery mildew are easily recognizable. 

• Initially, greyish white powdery spots appear on the leaves, stems and flowers.
• As the disease progresses, the leaves become yellow and brittle and may eventually fall off.
• In severe cases, the entire plant may become covered in a white powdery coating.

Control Measures

There are several strategies that can be used to control powdery mildew in roses, including cultural practices, crop sanitation, crop diversification, biological control, and chemical control.  

Cultural Measures

The following are some of the cultural practices that can help reduce the incidence of powdery mildew in roses, 

• Provide adequate spacing between the plants to ensure proper air circulation and sunlight for the plants.
• Remove all the weeds and debris from rose beds to prevent the buildup of inoculum.
• Water the plants at the base to avoid wetting the foliage, which can increase humidity and promote fungal growth.
• Crop diversification, which involves rotating crops in a given area can reduce the build-up of pathogens. This can help reduce the severity of powdery mildew in roses.

Mechanical Measures

• Collection and destruction of infected plants parts can reduce the spread of powdery mildew in roses
• Pruning of infected plant parts should be done as soon as they are observed.

Biological Measures

• Anand Dr Bacto’s Ampelo Bio Fungicide contains Ampelomyces quisqualis which is a natural hyper parasite of powdery mildews that penetrates the hyphae wall of host cell and grows inside causing degradation of cytoplasm and result in death of pathogen. The recommended dosage is 2.5 ml per liter of water.
• Anand Dr Bacto’s Fluro Bio Fungicide contains an effective microbial culture Pseudomonas fluorescence which prevents the growth of target fungi. Mix 5 ml of sun bio monus in 1 litre of water and spray during early morning or late evening hours for effective results.
• Mildown Bio fungicide contains Bacillus subtilis which competes with the disease-causing organisms and induces systemic acquired resistance against bacterial pathogens. Treat the rose saplings with Mildown at 5 ml per liter of water before planting.

Chemical Measures

Chemical control can be effective in managing powdery mildew in roses. Some commonly used fungicides for powdery mildew in roses include, 

Product Name	Technical Content	Dosage
Bavistin Fungicide	Carbendazim 50%WP	2 gm/lit of water
Contaf Plus Fungicide	Hexaconazole 5 % SC	2 ml/liter of water
Amistar Top Fungicide	Azoxystrobin 18.2% + Difenoconazole 11.4% SC	1 ml/lit of water
Saaf Fungicide	Mancozeb 63% + Carbendazim 12% WP	2 gm/lit of water
Roko Fungicide	Thiophanate Methyl 70% WP	0.5 gm/lit of water
Sultaf Fungicide	Sulphur 80% WP	2 gm/lit of water