Lenten Rose Diseases

Bacterial Leaf Spot

• Bacterial leaf spot, scientifically named Pseudomonas spp. or Xanthomonas spp., is a bacterial disease that can affect lenten roses. Once the bacteria infects the plant, the leaves begin to show discoloration, usually in the form of dark brown or reddish brown blister-like spots. The bacteria cannot survive for very long in soil and must enter a plant through an open hole or wound to infect it. Because there are no known antibacterial chemicals to kill the two strains of bacteria that cause leaf spot, the best way to manage the disease is by prevention. One way to prevent bacterial leaf spot is to avoid pruning or working on lenten roses when they are wet because moisture helps to spread the disease. Cutting away leaves or stems infected with spots can also deter the spread of the bacteria.

Botrytis Cinerea

• Botrytis cinerea, also commonly called Botrytis blight, is a type of fungal disease common among many types of ornamental flowers, including lenten roses. Botrytis cinerea is most common in warm, moist climates because the fungi thrives in these conditions. Symptoms include irregularly shaped brown, mushy spots on the rose petals. If the fungus attacks the rose before it has bloomed, the blooms can fail to open. Botrytis can be prevented by keeping the roses from becoming overly damp and by cutting away any diseased blooms as soon as they appear.

Root Rot

• Root rot is a common disease that affects many types of plants, including lenten roses. Root rot occurs when the soil becomes saturated with water, turning the flower's roots gray and mushy. Flowers and leaves begin to wilt and die and new blooms fail to open. Stems near the soil can also become mushy and water-soaked. The best way to prevent root rot is to keep the soil well drained and avoid over-watering the plant. The soil should be slightly damp to the touch, but never overly saturated with water puddles near the plant.

Powdery Mildew

• Powdery mildew, or Sphaerotheca pannosa, is caused by a type of fungus that affects many rose varieties, including lenten roses. Powdery mildew appears as a white or gray growth on the plant's stems, leaves or buds. As its name suggests, the growths are powdery in appearance. Powdery mildew does not grow well in direct sunlight, so shaded roses are often affected. The disease can be prevented by planting lenten roses in sunny areas and pruning away any diseased parts of the plant. This will help deter the spread of the growths.