While roses can be a popular choice for landscaping, these flowers can be easily susceptible to a number of diseases. Two such diseases are black spot and downy mildew.
Black spot is caused by the fungus Diplocarpon rosae, and is one of the most prevalent rose diseases in Connecticut. Roses infected with black spot disease have leaves that begin to show circular black spots, often surrounded by yellow halos. Premature discoloration of the rose’s leaves is common and can cause leaves to fall prematurely. Plants that defoliate too early in the season are particularly susceptible to winter injury.
In addition to symptomatic leaves, rose plants infected with black spot can also present with purple-red blotches on their canes that progress into cankers for the fungus to survive over the winter months.
There are a number of strategies that can be used to manage black spot on rose plants. Planting resistant varieties, providing sufficient space between plants for adequate air circulation, and avoiding watering roses early in the day can all help to prevent an outbreak. Once an outbreak has occurred, proper sanitation and pruning can help to control the spread of the disease to surrounding plants.
In addition to black spot, roses may also become affected by another fungal disease known as Downy mildew. This disease is one of the most highly destructive diseases for rose plants, but luckily is relatively sporadic in Connecticut. Cool, wet conditions promote the growth of this fungus and the disease is characterized most by purple to red angular spots or blotches.
In all cases of disease management, sanitation of infected plants is crucial to preventing the spread of disease to healthy plants. Additionally, sound arborist practices to help maintain the plant’s vigor should be exercised. Call or text Eric for a free consultation to discuss how our arborist services can keep your landscape healthy for years to come.