Botrytis General Information

Botrytis blight or gray mold is a fungus disease which infects a wide array of herbaceous annual and perennial plants.

This type of mold is referred to some as “grey rot” but is known by winegrowers as “noble rot”

Botrytis Species Information

30+ species. Ubiquitous.

Botrytis Growth Characteristics

This mold grows in soil, stored and transported fruit and vegetables. Plant pathogen and saprophyte on flowers, leaves, stems, fruit. Leaf rot on grapes, strawberries, lettuce, cabbage, onions.

There are several species of the fungus Botrytis which can cause blights; the most common is Botrytis cinerea. Botrytis infections are favored by cool, rainy spring and summer weather usually around 15C (60F). Gray mold can be particularly damaging when rainy, drizzly weather continues over several days.

Botrytis cinerea can infect many ornamental plants including: anemone, begonia, calendula, chrysanthemum, dahlia, dogwood,fuchsia, geranium, hawthorn, heather, hydrangea, marigold, pansy, periwinkle, petunia, rose, snapdragon, sunflower, sweet peat, violet, zinnia.

Two other damaging Botrytis blight fungi have strict host preferences: Botrytis paeoniae infects peony, and Botrytis tulipae infects tulip causing the disease known as tulip fire.

Among vegetables and fruit, Botrytis cinerea can infect asparagus, bean, beet, carrot, celery, chicory, crucifers, cucurbits, eggplant, endive, grape, lettuce, onion, pepper, potato, raspberry, rhubarb, rutabaga, shallot, strawberry, tomato, turnip, and others

During wet or humid weather, examine any brown or spotted plant material that develops, and look for masses of silver-grayspores on the dead or dying tissue. These spores are readily liberated, and may appear as a dust coming off of heavily infected plant material. Some species of Botrytis form tiny black resting stuctures called sclerotia that may be evident on dead plant tissue in late summer. Not all species of Botrytis readily form these, so they may not be observed on all plants

Casual Organism and Disease Cycle

Botrytis bunch rot is caused by the fungus Botrytis cinerea. The fungus overwinters in grape mummies, dead grape tissues, and other organic debris in and around the vineyard, as well as on a multitude of alternate plant hosts. Because of its wide host range, growers always should assume that the fungus is present in the vineyard. In spring, the fungus germinates from small, dark, hard resting structures known as sclerotia. The fungus then produces spores (conidia) that spread the disease. These spores are produced throughout the growing season. As blooms die, the spores germinate and colonize dead flower parts. Using the dead tissue as a food base, the fungus invades living tissue. After penetrating the berry, the fungus may remain dormant until the fruit sugar content increases and the acid content decreases to a level that supports fungus growth. Symptoms then develop readily under warm, moist conditions.

Berries that escape bloom-time infection may become infected at or near harvest under favorable environmental conditions. Any wound on the berry provides an excellent infection site for the fungus even in the absence of favorable environmental conditions. Birds, insects, hail, and powdery mildew are common causes of wounds. Swelling during ripening in tightly packed clusters causes pressure that also can rupture the berries. Wet and humid conditions around the berries and leaves greatly enhance disease development. The longer wet conditions persist, the greater the probability of infection, even to undamaged berries. Warmer temperatures also favor infection. At 54 to 75 degrees F, infection occurs in 12 to 24 hours, while at 37 degrees F, 60 to 72 hours are required

Where is Botrytis found?

These types of mold can be found in temperate or subtropical areas. Dry spore distributed by wind and rain.

Often found growing on indoor plants.

Is Botrytis Allergenic?

This mold is a potential allergen. Some of people may experience hay fever, asthma or Winegrower's lung.

Toxins Produced by Botrytis

It is unknown if this type of mold produces toxins

Botrytis Health Effects

These moldscan present risk to humans and lead to rare cases of keratomycosis.

Botrytis Uses

Industrial uses are unknown.

How to test for / identify the presence of Botrytis

It can be identified via air and direct sampling methods.

Is Botrytis a "black mold"