Bougainvillea Fungus

Fungal Diseases

• Although there are many species within the Cercospora genus that cause leaf spot in a variety of plants, the official culprit on bougainvillea is Cercospora bougainvilleae "Muntanola," or Passalora bougainvilleae. This disease requires warm, wet conditions to get a toehold in the garden. Root rot, another common fungal disease, is caused by various species within the Phytophthora genus. Heavy, wet soils contribute to root rot.

Symptoms

• Leaf spot is evidenced by light to medium brown circular spots on the foliage. The spots generally, but not always, have a yellow "halo" around them. Leaves eventually fall from the bougainvillea. Root rot symptoms are easy to spot and include wilting, stem dieback and yellow foliage. Because a plant's roots anchor it to the soil, if the bougainvillea appears to be listing or dying at the soil, suspect root rot.

Control

• Remove affected stems, foliage and flowers from a leaf-spot infected bougainvillea. Rake the soil beneath the plant to remove fallen leaves and flowers and bag and dispose of everything. Spray the bougainvillea with copper sulfate or other fungicides labeled for use on the bougainvillea to control the spread of leaf spot. Unfortunately, there is no cure for root rot and infected bougainvillea should be removed and destroyed. Take cuttings first if you'd like to propagate new plants.

Prevention

• There are a number of ways to prevent bougainvillea leaf spot. Broad-spectrum fungicide sprays act as preventive measures. Trim off closely-growing foliage from overhead trees and other plants in close proximity. This allows for better air circulation around the bougainvillea. Water the plant at the soil, not overhead. To prevent root rot, allow the soil to dry completely before watering the bougainvillea. If you are growing a potted plant, empty the tray beneath the pot after watering. Amend soil that doesn't drain well.