Gray mold Botrytis cinerea on strawberries – fruitweb forecast model

Gray mold (Botrytis cinerea) is the fungal disease of greatest importance on strawberries grown in the field. Prolonged wet weather during flowering can lead to very large crop losses. The fruitweb forecast model can be used to identify the infection periods for Botrytis cinerea during flowering and to estimate how high the risk of infection is for later fruit infestations (red area). The strength of infection is calculated based on the air temperature and the duration of leaf wetness. Studies by Bulger have shown that the level of potential fruit infestation can be estimated very well in this way.

Required weather parameters

  • Rain
  • Air temperature
  • relative humidity
  • Leaf wetness (optional)

Leaf wetness is a very important parameter for calculating the risk of Botrytis cinerea infection. If your weather station does not have leaf wetness sensors, this parameter is calculated from the known parameters of rain, air temperature and relative humidity. However, this is associated with a certain loss of quality in the forecast.

The forecast model graph


Botrytis cinerea Erdbeere Modell


  1. Infection strength (proportion of potentially infected fruits)
  2. Temperature
  3. Relative humidity
  4. Rain
  5. Leaf wetness
  6. Infectious conditions

The infections with Botrytis cinerea that are relevant for the damage occur during flowering. If the leaves are wet for a long time in conjunction with temperatures between 15 and 25°C (the optimum temperature is 20°C), the flower organs, especially the sepals, will be attacked. Starting from these, the ripening fruits are then colonized.

The actual severity of the fungal disease depends primarily on the weather conditions during flowering. Therefore, only this period is taken into account in the fruitweb forecast model.

In the field, the weather during fruit ripening also has a certain influence on the severity of the disease. Since this can no longer be influenced by plant protection measures, this aspect is not taken into account in the model.


Bulger, M. A., Ellis, M. A., and Madden, L. V. 1987. Influence of temperature and wetness duration on infection of strawberry flowers by Botrytis cinerea and disease incidence of fruit originating from infected flowers. Phytopathology 77:1225-1230.