See:
Garlic (Allium sativum) - Blue Mold Rot
Tulip - Penicillium Bulb Rot (Blue Mold)
Cause The fungi Penicillium digitatum, P. gladioli, and P. hirsutum have all been reported from Washington. These fungi survive on infected bulbs and generally attack bulbs weakened or injured by other factors, especially injured bulbs stored under moist conditions. Many also have been reported on other bulb crops including crocus, gladiolus, onion, and tulip.
Symptoms In the field, scattered plants fail to emerge; others form weak, stunted shoots that yellow and die. Stems and leaves have a mushy rot with a distinctive sour odor. Infected fleshy scales are first soft and water soaked, white to greenish gray, and later hard and yellow or brown.
Older spots on the side of the bulb often appear as dead brown cavities containing masses of blue-green spores. Sunken, dead, brown husks, usually split in the center, cover these cavities. Infection often starts at wireworm punctures or other bruised or injured areas. When the rot begins at the base, the bulbs usually decay completely in the soil.
During late storage in sheds and in cool, moist precooling rooms, bulbs and emerging roots often become covered with a bluish-green fungal growth. The rot can progress rapidly and cause considerable loss, particularly when bulbs are forced.
Cultural control
- Dig bulbs when mature.
- Avoid bruising bulbs, especially when digging.
- Avoid sunburn and desiccation.
- Chill rapidly and keep dry.
- Discard all infected bulbs.
- Plant early but avoid wet soils.
- Disinfect trays and tools.
Chemical control Postharvest soak within 48 hours after digging.
- 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. Temperatures should be 55°F to 75°F. Soak bulbs 10 to 15 min, then let dry. Group 1 fungicide. 12-hr reentry.
- 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 fungicide. 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 Doss, R.P., Cascante, X.M., and Chastagner, G.A. 1989. The influence of infection with Penicillium corymbiferum on the forcing performance of wounded or unwounded bulbs of iris cultivars Ideal and Blue Star treated with ethylene or ethephon. Scientia Horticulturae, 39:161-166.