Cause Chrysanthemum stunt viroid. Contaminated cutting knives can spread the viroid. Handling infected plants before touching healthy plants can also spread this disease. The viroid has a large host range and may be symptomless in some plants. Infected plants may not flower correctly in response to controlled photoperiod. Symptoms may become more severe when temperatures reach 80°F to 84°F.
Symptoms Leaves and flowers are smaller than normal, with some bleaching. Plants are stunted to about half normal size with a tendency to more upright growth and premature (7 to 10 days) blossoming. Cultivars vary widely in symptom expression.
Cultural control
- Use cuttings only from healthy, viroid-indexed stock.
- Disinfect cutting tools between sets of stock plants.
- Isolate and contain new shipments for an observation period. Locate the isolation area well away from existing blocks or out-going shipments, and scout regularly.
- Rogue out all diseased plants.
- After handling diseased plants, wash hands thoroughly with soap before touching other chrysanthemum plants.
Reference Hosokawa, M., Ueda, E. Ohishi, K., Otake, A., and Yazawa, S. 2004. Chrysanthemum stunt viroid disturbs the photoperiodic response for flowering of chrysanthemum plants. Planta 220:64-70.