Informational table showing disease name, symptoms, pathogen/cause, and management of Dieffenbachia diseases. Disease Sympoms Pathogen/Cause Management Anthracnose Circular to oval brown leaf spots have a yellow halo. Spots may become two inches in diameter and contain tiny black fungal fruiting structures. Colletrotrichum gloeosporioides Avoid overhead watering.Apply a fungicide to protect healthy plants. Bacterial Leaf Spot Small gray or dark green leaf spots enlarge and become irregularly shaped, tan, dark brown, or black. Erwinia carotovora or Erwinia chrysanthemi Purchase plants free of the disease. Remove infected leaves and water in a manner that keeps the surface of the leaves dry. Wilt Lower leaves yellow, wilt, and die. Drought Maintain even soil moisture. Marginal Leaf Burn Margins of leaves brown and die. Over-fertilization Do no over-fertilize. If no slow-release fertilizer is present, leach the potting medium. Myrothecium Leaf Spot Large gray-brown, oval leaf spots form at leaf tips or margins. Fungal fruiting structures form in concentric rings within the spots on the underside of the leaf. Myrothecium roridum Do not apply excessive amounts of nitrogen fertilizer. Apply a fungicide to protect healthy plants. Nitrogen Deficiency Plants are yellowed with smaller than normal leaves and short internodes. Lack of fertilization. Apply a balanced fertilizer solution. Virus Leaves have a mosaic of light green where they should be dark green. Plants may be stunted, and leaves deformed. Some cultivars die within a month of infection. Dasheen mosaic virus Discard infected plants. Maintain good aphid control. Disinfests tools used on the plants.

Prepared by Gary W. Moorman, Professor of Plant Pathology