Weigela Diseases

Weigela is a flowering perennial shrub with a branched form and lovely trumpet-shaped flowers during the spring and summer. This plant is generally easy to grow and not very demanding, especially once it has settled in. Common diseases that impact weigela are black spots, anthracnose, botrytis, and powdery mildew. Most of these diseases result from bacteria and are caused by cramped or overly damp conditions. Learning how to identify and treat these diseases will improve the health of the weigela and ensure the plant is thriving and blooming.

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Weigela Black Spot

Black spot is a fungal disease that impacts foliage. The spots will likely appear after rainfall or when the weigela is grown in moist, damp conditions. Plants left untreated will eventually lose their foliage, severely impacting growth.

Identifying Black Spot

Dark black circles form on the top and underside of the foliage. The outer edges of the black spots are ragged, creating an inconsistent border. The spots will slowly engulf the infected leaf and merge into larger spots. Infected leaves will eventually fall from the plant.

Treating Black Spot

Treat black spot on weigela by removing infected leaves, dead growth, and debris around the plant. The goal is to improve airflow and dry out damp conditions. Prune leggy plants and avoid placing new plants too close, so air can circulate around the leaves. Avoid getting the plant wet by watering the ground instead of spraying water on the foliage.

Weigela Anthracnose

Anthracnose is a fungal infection that impacts weigela and is caused by a lack of airflow. The fungus that causes anthracnose lives in dead plant material around the plant. The fungus can spread from the debris to the healthy plant and continue to spread throughout the foliage. Plants with a heavy infection will experience leaf drop and potentially die from a lack of foliage.

Identifying Anthracnose

Anthracnose appears as purple-edged brown spots. The center of the spots will turn black, and the leaves will eventually wither and fall off the plant.

Treating Anthracnose

Treat anthracnose on weigela by removing debris from around the shrub. Rake dead leaves and remove downed branches. Trim lower branches to shape the plant and ensure air can flow around the base of the plant. Apply a layer of mulch to prevent spores from splashing up and onto the plant when watering.

Weigela Botrytis

Botrytis is a fungal disease. Like most other forms of fungus, botrytis thrives in damp, wet conditions. The mold will overtake the plant with time and prevent the leaves from conducting photosynthesis, slowly killing the weigela.

Identifying Botrytis

Botrytis appears as a gray mold on weigela. The mold grows on the leaves, flowers, and stems and spreads throughout the shrub.

Treating Botrytis

Treat botrytis on weigela by removing the infected parts of the shrub. Destroy the infected parts to prevent further spread of the fungus. Water the weigela in the morning, so the foliage can dry during the day, and remove debris from the ground around the plant. Airflow is the best defense against fungi like botrytis. Make sure the shrub is receiving plenty of sunlight. Spray the plant with a fungicide in extreme cases.

Weigela Powdery Mildew

Powdery mildew is a fungus that grows on the top of leaves. Increased humidity and cool nighttime temperatures contribute to powdery mildew. Infected leaves will ultimately die, although the disease is rarely fatal. Untreated, powdery mildew is unsightly and will spread throughout a weigela shrub.

Identifying Powdery Mildew

Identify powdery mildew by the white powdery coating that grows on the top surface of the leaves. Infected leaves will later curl and wither.

Treating Powdery Mildew

Treat powdery mildew on weigela by pruning and discarding severely infected foliage. Properly space shrubs when planting so air can flow around each plant and ward off dampness. Prune weigela during dormancy to expose the center to more sunlight and airflow. Select cultivars that are resistant to disease.

Weigela Disease Chart

Disease

Identifying

Treating

Black Spots

Black spots on top and underside of leaves

Prune/discard infected foliage and improve air circulation

Anthracnose 

Brown spots with purple edges on leaves

Trim infected foliage and improve air circulation

Botrytis

Gray mold on leaves, flowers, and stems

Remove infected foliage and improve air circulation

Powdery Mildew

White powdery coating on leaves

Remove infected foliage and improve air circulation

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Author Alison Cotsonas - Published 07-07-2023