Diseases of Gardenia Buds

Chief Problems

• A major disease of gardenia buds is stem canker. You can spot this type of disease if you see areas of the plant that appear cracked, or ulcerous lumps near the ground. In addition, sooty mold makes gardenia leaves appear black. The black color actually blocks sunshine from getting to the foliage and therefore inhibits the progress of photosynthesis. Photosynthesis is the process by which plants turn the sun's energy into sugar energy. Pests like scales and whiteflies actually produce a sticky substance called honeydew, which attracts sooty mold.

Leaf Spot

• Several other diseases can also affect gardenias. Bacterial leaf spot is characterized by tiny oval spots on new leaves. The middle of the spot is a yellowish hue, but this area eventually becomes a red spot surrounded by yellow. If a gardenia plant is heavily attacked by the bacteria Pseudomonas gardenia, the plant could lose all of its leaves. The fungus Cercopsora also causes leaf spot. With leaf spot, gardenia plants feature dead areas that look almost black. Leaves on an infected plant typically drop earlier than normal.

Other Diseases

• Bud drop occurs when gardenia plants' buds collapse when the temperature at night is high, or when the amount of sunshine is lacking. These buds essentially die off just before blooming. The fungus Erysiphe polygoni causes a gardenia bud disease known as powdery mildew. You will notice powdery mildew by the presence of dusty white blotches on gardenia plant leaves.

Control

• Get rid of diseased gardenias to prevent infection, especially stem canker, from spreading to other plants in your garden. Destroy insects such as whiteflies and scales to keep sooty mold at bay on your gardenia plant buds. In addition, apply a fungicide to your gardenia plants when tackling disease problems such as powdery mildew and leaf spot, following the manufacturer's instructions.