Cause Pseudomonas cichorii, a bacterium. Warm, humid conditions such as frequent misting favor disease development on schefflera. Older, more mature leaves are more susceptible. The bacterium can survive on a wide range of host plants including many ornamentals, flowering plants, and vegetables.
Symptoms Lesions are tan to black with a bright yellow halo. They may also be irregularly shaped. The center of the necrotic area may be tan if allowed to dry out. Leaf drop is common under high moisture conditions. May be confused with a fungal leaf spot caused by Alternaria.
- Reduce leaf wetness.
- Increased fertility will help protect healthy leaves.
- Provide morning sun and temperatures between 50°F and 80°F. Water moderately and allow the plant to dry between waterings. Repot frequently.
- Phyton 27 at 2 to 5 oz/10 gal water. Group M1 fungicide. 48-hr reentry.
Reference Chase, A.R. 1987. Compendium of Ornamental Foliage Plant Diseases. St. Paul, MN: APS Press.