See:
Garlic (Allium sativum) - Blue Mold Rot
Iris, Bulbous (Iris spp.) - Blue Mold
Cause Various Penicillium spp., fungi. Penicillium hirsutum has been found on Iris in Washington. Both P. hirsutum and P. tulipae produced more pronounced symptoms than other species in Denmark. These fungi generally attack bulbs weakened or injured by other factors, especially injured bulbs stored under moist conditions. These fungi have also been reported on other bulb crops including crocus, gladiolus, iris and onion.
Symptoms Brown spots develop on bulbs in storage. A blue moldy growth may develop on the bulb, basal root plate or between the scales. Internal discoloration of leaf initials and surrounding tissues may develop. The entire bulb may be affected and become hard and dry. Sprouted blubs can have reddish stunted foliage.
Cultural control
- Dig bulbs at the proper time and carefully handle to avoid injury such as bruising or sunburn.
- Store with moderate humidity and gentle air circulation.
- Destroy diseased and damaged bulbs.
- Use long rotations before replanting tulips again on the same ground. Remove volunteer plants from previous bulb crops.
Chemical control Postharvest soak of sorted bulbs then dry thoroughly and quickly before storage. Resistant fungi have been detected and may render these treatments ineffective.
- KleenGrow at 0.15 to 1.5 fl oz/gal water. Soak for 30 seconds and allow to drain.
- Mertect 340 F at 30 fl oz/100 gal water at 55°F to 75°F. Soak bulbs 15 to 30 min, then let dry. Group 1 fungicide.
- Thiophanate-methyl-based products as a postharvest soak at 80°F to 85°F. Soak clean bulbs 15 to 30 min. within 48 hours after digging. Group 1 fungicides. 12-hr reentry.
- Cleary's 3336 EG at 16 to 24 oz/100 gal water.
- OHP 6672 4.5 F at 16 to 20 fl oz/100 gal water.
Reference Overy, D.P., Frisvad, J.C., Steinmeier, U., and Thrane, U. 2005. Clarification of the agents causing blue mold storage rot upon various flower and vegetable bulbs: implications for mycotoxin contamination. Postharvest Biology and Technology 35:217-221.