Michigan State University Extension
Ornamental Plants plus Version 2.0 - 00000526
01/01/98
Bacterial leaf spot causes very small, yellow or yellowish-orange spots with translucent centers. The spots enlarge up to 1/2 inch and run together. Under drier conditions the spots do not enlarge but turn reddish brown giving a speckled appearance. Numerous spots cause infected leaf parts to yellow, wilt and die. Under moist air conditions large mounds of bacterial ooze appear on the lower surface of the spots. Dried ooze is a waxy, silvery-white layer covering the spots. The ooze may later appear on the upper surface of the spots. Prevention includes avoidance of lower temperatures, crowding and syringing.
A fungal leaf spot causes very small reddish brown lesions on the young leaves. On unrolled leaves, the spots may be 1/4 inch or more in diameter with a dark brown border. When the lesions run together yellowing and death of the entire leaf occur. The infection can occur through wounds caused by mealybugs. Keep the temperature and humidity down and control mealybugs.
Stem and leaf rot causes brownish, water-soaked, sunken areas in the stem. The leaves have irregular brownish soft spots.
At least two root and stem rots will cause rotting of roots and lower stems.