Mold-Blue Mold on Lily Bulbs

What is Mold?

Molds are fungi that are microscopic in size. It is created by damaging the bulb. And storing in too wet of conditions. Equally important, wet packing material or too much humidity. Once a lily bulbs is damaged then stored too wet, the damaged scales start rotting. Therefore, the mold fungi appears. It will most often appear white then turn blue in color. The blue color are the fruiting spores. Even though they can approximate bacteria size, molds are eukaryotic organisms. That is to say, their genetic material is enclosed within a specialized membrane that lies in the interior of the organism.

Molds are present in virtually every environment that has been examined. Molds grow indoors and outdoors and, depending on the species, can grow year-round, even in winter. In the natural environment, molds are important and desirable because they hasten the decomposition of organic material such as fallen leaves and dead trees. Indoors, however, mold growth is undesirable. For humans, the molds that grow indoors can be of particular concern. This is because these can cause allergic reactions in those people who are sensitive to the compounds produced by the molds. Most common indoor molds are: Cladosporium, Penicillium, Alternaria, Aspergillus, and Mucor.

Molds reproduce by releasing spores (essentially packets that contain the genetic material necessary for the formation of a new mold). Spores can float through the air. And, if landing in a hospitable environment, can germinate to form a new mold. One of the essential components of a hospitable environment is moisture. All types of mold all require a moist surface for growth.

What is Blue Mold?

Blue mold rot, is a fungal disease caused by Penicillium spp. Penicillium mold is a common soil fungus, that survives on dead or dying plant debris. With secondary infections by Cylindrocarpon and related fungal species. Lily bulbs have no natural protective layer. Therefore, bruised easily which can lead to severe rot. The fungus invades the lily bulb through wounds on the bulb. And decaying stem tissue. Once the fungus has invaded the bulb it grows rapidly, and may sporulate on the surface of a wound. Appearing as a blue-green furry coating. Optimum temperatures growth are between 70 F to 77 F. with high relative humidity.

Penicillin mold occurs on bulbs in storage. And infects mostly their outer scales where there has been harvest damage. Also, indicates early signs of rot. Equally, can be severe enough to destroy bulb(s). The rot develops rapidly in storage, particularly in cool, humid conditions. And can pass from the storage medium to uninfected bulbs/corms/tubers. The fungus grows well at low temperatures (its cousins affect fruits in the refrigerator). And can be recognized by chocolate-brown areas throughout the scales. The bulbs may be soft or “mushy” to the touch, and covered with a blue-green mold. Likewise, white fungal growth. Particularly prevalent in early dug bulbs that have suffered mechanical injury, insect damage, bruising, stress. Similarly, infected with basal rot or any other bulb disease.

Is Mold terminal?

Bulb rot is terminal if the bulbs are severely damaged after lifting/harvesting. Also, seriously infected with a bulb disease or rot. Therefore, left unchecked, the disease can become rampant causing them to rot. Consequently, destroying the bulb(s). Some varieties are more susceptible than others. Such as Oriental Hybrids. However, slightly damaged bulbs or their scales, Penicillin mold will not harm lily bulbs. And the mold will simply die upon planting not contaminating your soil.

Primary Plants That Are Affected

Primary plants that are affected by blue mold or Penicillin mold are: any plant grown from a bulb, corm, or tuber. Additionally, onions, garlic, day lily, lilies (lilium), crocuses, cyclamens, freesias, gladioli, hyacinths, irises, narcissi (daffodils), scillas, tigridias and tulips.

Healthy Lily Bulb: Lilyflowerstore

How to Prevent Mold

Bulbs/corms/tubers damaged are susceptible to infection through wounds. So, careful handling is important during harvest, storage.  Also, bulbs should not be exposed to direct sunlight. As a result, this can damage them. No damaged bulbs/corms/tubers should be stored. Likewise, when harvesting or lifting your lily bulbs for winter storage, ensure they are dry. Leave some soil on the surface in warm, dry weather for a few days, before storing. Moreover, good air circulation while storing for long periods is essential!

I recommended not storing them in wet Peat Moss. Damp to the touch, not wet. Peat Moss is very fine textured.  Holds too much moisture, does not allow for good air circulation. And will absorb moisture from surrounding conditions. It is good for shipping bulbs. But not for storing over a long period of time. Instead of Peat Moss, I recommend a slightly damp potting mix. Equally, with enough pumice or perilite. Therefore, it allows very good air circulation. Keep the storage conditions dark, cool, dry and well ventilated. Equally preventing humid conditions which the disease can spread.

How to Get Rid of Mold

Extreme Cases: Again, blue mold normally is only a temporary condition. Unless it is feeding off a more serious condition. For example, basal rot, bulb rot, bruised or damaged scales. And is appearing inside or between scales. Check this by gently pulling back the tip of the scale. Without detaching it from the base of the bulb. Then, look inside. Destroy any bulb that is showing extreme signs of Blue Mold. However, possibility of saving the bulb is fair.  Dipping the bulb(s) in a fungicide such as Captan or Cleary’s might save it.

Moderate to Slightly Affected: If a bulb scale shows signs of blue mold on a break or cut. This type of condition is usually not serious. You can simply plant the bulb as is. As well as, wipe the blue mold with a damp cloth. Then plant it.


Best control methods for preventing a serious infection of Blue Mold is. 1.) Avoid any damage to the bulb. 2.) Keep peat moss damp to the touch. This pathogen gains entry through open wounds, wet conditions. Equally important, properly clean and dry the lily bulbs prior to storage. Then, store the bulbs at 36 degrees F or less. And with low relative humidity.

References:Oregon State University, Ohio State University, Wikipedia

Pictures: Copyright Lilyflowerstore All rights Reserved

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