Botrytis blight disease of rose, also called gray mold. It’s a fungal disease caused by Botrytis cinerea. This disease affects a wide variety of ornamental plants, including roses, and can cause significant damage to the plants. Botrytis cinerea is a necrotrophic fungus that obtains nutrients by killing and decomposing plant tissues.
Botrytis Blight Management in Rose
The causal organism of Botrytis blight Disease
The most common causal organism of Botrytis blight is Botrytis cinerea. In addition to these fungal pathogens, several factors, such as high humidity, cool and damp weather, poor air circulation, overcrowding of plants, and physical damage to plant tissues, can all contribute to the development and spread of Botrytis blight.
The Disease cycle of Botrytis blight Disease
The disease cycle of Botrytis blight, also known as gray mold, involves several stages that are influenced by the environment, such as temperature, humidity, and the presence of plant tissue.
- Spore production: The disease cycle begins when Botrytis produces spores easily disseminated by air currents and splashing water.
- Spore germination: When spores land on a suitable host plant, they require a film of moisture for 8 to 12 hours to germinate and infect the plant. Relative humidity of 85% or greater and temperatures between 55-75°F are optimal for spore germination.
- Infection: Once the spores have germinated, they penetrate the plant tissue and begin to colonize at a wide range of temperatures, with an optimum range of 60-75°F. The fungus can infect various plant parts, including leaves, stems, flowers, and fruits.
- Disease development: The fungus grows rapidly and produces a gray, fuzzy mycelium mass on infected plant tissue. The affected tissue becomes water-soaked, soft, and often has a water-soaked margin. Eventually, the infected tissue becomes necrotic and dies, leading to serious damage to the plant.
- Spore dispersal: The fungus produces new spores that can be disseminated by air currents or water splash, thus continuing the disease cycle.
Causes/Conditions favorable for Botrytis blight disease spread.
- Botrytis blight disease is favored by high humidity and moisture. It can be spread by air currents, splashing water, and physical contact with infected plant parts.
- Wounds in plant tissues provide entry points for the pathogen to invade and colonize the host. Botrytis blight is more in the spring and fall months when temperatures are cooler and relative humidity is high.
- The pathogen also produces infectious propagules such as sclerotia that can survive in the soil or plant debris for long periods, providing a source of inoculum for subsequent infections.
- Overcrowding plants and poor air circulation can create conditions conducive to spreading the disease, as can excessive nitrogen fertilization, which promotes rapid vegetative growth that can be more susceptible to infection.
- Botrytis blight can also be favored by plant stress caused by drought, heat, or insect damage, which can weaken the host plant and make it more vulnerable to infection.
Symptoms of Botrytis blight disease
Symptoms of Botrytis blight disease can vary depending on the plant species affected and the stage of infection. However, some common symptoms of the disease include:
- Grayish-brown fuzzy fungal growth on flowers, leaves, and stems.
- Small flecks on infected petals.
- Sunken, grayish-black spots (lesions) at the base of infected flowers and stems.
- Cane blight, characterized by dark, sunken lesions on the stems, is often associated with wounds where flowers have been cut or the plants have been pruned.
- Wilting, discoloration, and eventual death of infected plant tissues.
- On cuttings taken for propagation, the fungus