By: - Updated: February 19, 2019


What Is Botrytis?

Botrytis is an anamorphic fungus of the Sclerotiniaceae family that passes for one of the most serious plant diseases, primarily known for infecting and affecting grapes as well as raspberries and also strawberries.

The most common species of Botrytis, Botrytis cinerea, is referred to as gray mold. It first attacks a plant in the form of a white growth before gray spores form which can be spread by water or wind. It occurs in both sexual (teleomorph) and asexual (anamorph) forms. Botrytis is a plant parasite, though some of its species are saprophytes.

Known Botrytis species

Botrytis has about 30 species that have been scientifically identified. The most common species is Botrytis cinerea which is subject to extensive study owing to its economic impacts. Botrytis faragariae is a new species which affects strawberries and is of great economic importance. Botrytis cinerea is exceptional in that it affects quite a wide variety of plant hosts, whereas other species only affect a few hosts with some being host-specific.

Other common species of Botrytis fungus are Botrytis anthophila, Botrytis allii, Botrytis fabae, Botrytis tracheiphila, Botrytis squamosa, Botrytis ampelophila, Botrytis artocarpi, Botrytis carnea, and Botrytis anacardii.

Botrytis conidiophores
Botrytis conidiophores

Adaptability of Botrytis

Adaptability refers to how an organism changes or adjusts to fit and survive in its changing environment. Over time, Botrytis species have proved to change to enable them to live in generations. For example, Botrytis cinerea has been found to exist in both phenotypic and genotypic variations.

Various Botrytis species have also developed resistance to some fungicides, thus being able to live in multiple environments.

Botrytis cinerea on Riesling grapes
Botrytis cinerea on Riesling grapes

Where to find Botrytis mold at home?

Botrytis mold frequents damp places at home. You can find the gray mold on wounded plant tissue or those that are almost dying, flowers that are fading, seedlings under moist conditions, leaves that have been damaged by sprays or suffer from mechanical injuries and leaves that infected flowers have fallen upon.

They are common outdoors but can also be found on plants that are grown indoors; wherever plants happen to be.

How to identify Botrytis?

To know that your plants have been infected by gray mold, be on the lookout for spots that appear whitish and look water-filled on the leaves, stems, buds, and petals.

These spots will start to turn greyish and finally brownish, making people confuse them for brown mold. If the humidity is extremely high at your home, you will notice web-like structures covering your leaves and spreading, making it appear like grey flowers from far.

These structures have fuzzy spores that become very active and can spread at the slightest activity.

What causes Botrytis?

Botrytis, or gray type of mold, is mainly caused by moisture. It occurs on wet plant surfaces and can infect any plant. It tends to affect injured plants or plants that are damaged and are on the verge of dying.

Botrytis cinerea on strawberry
Botrytis cinerea on strawberry

Once it infects any section of a plant, it can spread to other healthy parts of the plant. Spores can spread whenever triggered by any action, more so in a greenhouse.

Favorable conditions for Botrytis growth

Spores germinate under these favorable conditions:

  • An optimum cool temperature of 220C to 250C
  • Relative humidity of 85% and above
  • Loose moisture on the surfaces of buds, leaves, and stems
  • Poor ventilation and air circulation

Benefits of Botrytis

Botrytis is generally harmful to plants. However, as they feed on plants as saprophytes, they lead to decay and decomposition, hence contributing to biomass. If it is ensured that it doesn’t multiply and cause harm to other plants, this becomes a positive impact and adds to the growth of the plants.

Botrytis cinerea dehydrates grapes, thus increasing sugar concentration. This leads to sweeter wine with unique flavor as compared to uninfected vines.

Effects Of Botrytis on plants

This mold causes serious plant infections such as Onion neck rot. It is also associated with gray mold on seedlings as well as apple rot. The symptoms of the disease are rot, blight, wilting, and dark spots on the infected plant parts.

Effects Of Botrytis to humans

“Winegrower’s lung” is a very rare allergic reaction of the respiratory system that is caused by Botrytis cinerea in predisposed persons.

Preventing Botrytis Infection

When it comes to preventing Botrytis infection, the first step is to observe the highest possible levels of hygiene and make sure your plants are dry. Proper sanitation helps best.

When pruning or doing any maintenance for your plants, ensure you take extreme care not to cause any injuries. Botrytis can take advantage of such damages to infect the plant.

Botrytis blight of hibiscus flower
Botrytis blight of hibiscus flower

Also, clean thoroughly between your plants as often as possible, removing dead leaves, decaying matter, and debris. You might also want to ensure you space your outdoor plants well to allow for air circulation and minimize the spread of Botrytis if it ever occurs.

If transplanting, ensure you do not use plants parts that are infected or are damaged. You can alternate your plants to control Botrytis infection. Last but not least, ensure that humidity is lowered in greenhouses by heating and ventilation.

How to treat Botrytis?

First, clean your plants thoroughly to avoid spreading the disease to healthy plants. It is also advisable to employ the use of fungicide to control the spread of infection. Such fungicides include Thiram, Tebuconazole, Trifloxystrobin, Iprodione, and Chlorothalonil. Some Botrytis species, however, exhibit resistance to certain fungicides.

Another viable measure is to remove infected plants and plant parts and destroy them utterly. For infected strawberry plants, apply biochar; which is a form of charcoal to reduce its severity.

Use biological control agents for Botrytis control in greenhouses such as Bacillus subtilis, Trichoderma harzianum, Streptomyces griscoviridis, & Streptomyces lydicus.
Lastly, apply professional mold removal services of experts like Mold Busters.

Facts about Botrytis

  • If incubated for seven days on potato sugar agar at 250C, Botrytis grows very fast up to a diameter of 3-9cm.
  • Botrytis produces more than 60000 spores on a plant tissue as small as the smallest fingernail.
  • About 50% of greenhouse operations have proved resistance to dicarboximide fungicides (FRAC Group 2).