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• Identifying Botrytis
• Grey mold symptoms
• Conditions for development of Botrytis

When a plant is infected with botrytis, circular, greyish-brown spots appear on the leaves. Under humid conditions the spots can quickly expand. Hence, the plant rots away and can die in whole or in part. If the stem is affected, cuttings can wilt completely. The diseased parts usually have a brownish-grey trace mass, which spreads when the plants are touched.

Besides infecting stems, botrytis is known to be the main cause of fruit rot. Rotting Fruit is recognized by the fungal fluff that develops on decaying fruits such as strawberries. Other fungi also cause fruit rot such as Gnomia comari and Phytophthora. The botrytis affects the fruits, which triggers the fruits to become soft. It is often seen that botrytis appears after the fruits have been harvested.

Below are examples of symptoms from grey mold.  

​​​​Grey mold on roses​​​​

​​​​Grey mold on tomatoes​​​​

​​​​Grey mold on tomato stem​​​​

​​​​Grey mold on stem​​​​

​​​​Grey mold on cucumber stem​​​​

​​​​Grey mold on fruit​​​​

Botrytis cinerea spores are always present. Botrytis spores are easily spread by wind, humans and water. The spores germinate at a temperature between 2°C and 32°C. The optimum temperature is between 20°C and 25°C at an RH >80%. Spores need moisture to germinate. The minimum RH for germination is 90%. Wounds and condensation can provide enough moisture for germination. Infection can occur in many circumstances. Also in cold stores and in the post-harvest phase.

Stem damage in gerberas​​​​

​​​​Rotting head in gerberas​​​​

​​​​Stem damage in tomatoes​​​​

To prevent botrytis, it is important to keep the crop as dry as possible and the humidity as low as possible. Infections mainly occur under humid conditions. Also ensure good greenhouse hygiene. 

You can take a number of measures

• Provide an active climate in the greenhouse
• Ensure regular growth
• Do not let the crop get wet
• Make sure that the RH does not get too high in the greenhouse by using dehumidifiers, such as the DryGair
• Prevent damage/wounds to the crop
• Avoid leaf wet periods longer than four hours
• Remove affected plant material
• Cutting leaves instead of breaking leaves in tomatoes
• Preventively, apply a covering fungicide such as Serenade
• Avoid a crop that is too dense

The danger of Botrytis Cinerea is that the fungus spreads easily. It is important to be proceed with caution when removing affected plant parts. Store it directly in a plastic bag so that the spores cannot spread.

To control botrytis cinerea, you can use natural enemies and chemical crop protection agents. Our specialists will be happy to advise you on the various options for controlling this disease.

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