Rose Rust: Understanding, Diagnosis And Management

Rust is a common fungal disease that affects many species of plants, including roses. It is caused by a group of fungi in the Pucciniaceae family and is characterized by the formation of yellow or orange pustules on the leaves, stems and flowers. Rust disease can spread quickly from one plant to another, causing significant economic losses to the rose industry. 

Rose rust thrives in moist, warm and humid environments. The disease can develop in temperatures ranging from 15 to 30°C and is most severe in the rainy season when the humidity is high. The disease is also favored by overcrowding, lack of air circulation and damaged plant tissue which allows entry points for the fungus. 

Type of Infestation

The disease cycle of rose rust begins with the infection of leaves, stems or flowers by fungal spores. The fungus then penetrates the plant tissue and forms new infections. The pustules that form on the plant’s surface produce new spores, which are spread by wind and rain to other plants. The cycle can repeat itself several times in a season, leading to a severe decline in the plant’s health.  

Scientific Name: Phragmidium mucronatum 

Most Affected States

Rose rust is widespread in India and is commonly found in states such as Karnataka, Maharashtra and Tamil Nadu, which have a suitable climate for the development of the disease. 

Symptoms of Rose Rust

• Initially small, yellow or orange pustules develop on the undersides of the leaves. These pustules can enlarge and eventually cover the entire leaf surface.
• The affected leaves may turn yellow, wilt and eventually drop from the plant.
• Stems and flowers may also be infected, leading to the formation of pustules and distortion of the plant’s growth.
• In severe cases, the plant may become stunted, with reduced yields and poor-quality flowers.

Control Measures

Proper management practices are essential to control and prevent the spread of rose rust disease. The following are some of the key management strategies for rose rust: 

Cultural Measures

Preventive cultural practices can help reduce the severity of rose rust disease. These practices include: 

• Plant rust-resistant varieties or hybrids.
• Provide adequate spacing for the plants to allow good air circulation.
• Keep the field free from dead leaves and other debris which can provide a suitable environment for the fungus to survive and infect new plants.
• Water the plants at the base to avoid wetting the foliage in order to reduce the spread of the disease.
• Avoid applying excessive amounts of nitrogen, as this can lead to succulent growth that is more susceptible to rust infection.

Mechanical Measures

• Remove and destroy infected leaves and canes from the ground and surrounding area to reduce the source of rust inoculum.
• Prune off infected leaves and canes promptly and dispose of them properly to reduce the spread of the disease.

Biological Measures

• Katyayani Activated Neem Oil contains activated azadirachtin which when used at the rate of 5ml per liter water with a 12 days interval between each spray can effectively control rose rust.
• Fungo Raze Bio Fungicide contains natural plant extracts which can effectively control rust diseases in roses. Depending on the severity of disease, spray fungo raze bio fungicide at the rate of 1-2 ml per liter of water.

Chemical Measures

In cases where cultural, mechanical and biological control strategies are not sufficient to control Rust, chemical control may be necessary. There are several fungicides available for controlling Rust in roses, including:  

Product Name	Technical Name	Dosage
Tilt Fungicide	Propiconazole 25 % EC	1 ml/lit of water
Dithane M45 Fungicide	Mancozeb 75% WP	2-2.5 gm/lit of water
Saaf Fungicide	Mancozeb 63% + Carbendazim 12% WP	2 gm/lit of water
Blitox Fungicide	Copper Oxychloride 50 % WP	2 gm/lit of water
Sultaf Fungicide	Sulphur 80% W	2 gm/lit of water