Botrytis: life cycle & resistance management advice

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Botrytis primarily attacks tender, weak, wounded or dead tissue. Symptoms appear on infected flower petals as restricted lesions. Subsequently, these lesions become necrotic and spread to the whole petals and receptacle, finally resulting in collapse of the flower head and petal drop, causing reduced market value. On leaves, symptoms start as small, water-soaked spots that enlarge and coalesce, so infected leaves appear blighted. When stems are infected, black, sunken and elongated lesions can develop.

On bulbs, outer bulb scales may also be infected and show yellow to brown sunken lesions. Small, shiny, black fungal resting structures (sclerotia) may be visable on the surface of infected bulb tissue. Grey, fluffy mycelium evident on infected plant tissues is a characteristic of identifying Botrytis blight.


Proper sanitation inside and outside greenhouses, adequate ventilation and preventative applications of fungicides.

Botrytis Life Cycle

Understanding a disease's life cycle is vital to maintaining control in your crops. Below is the Botrytis life cycle:


Managing resistance 

Botrytis develops in a wide range of weather conditions and on almost all crops, as long as moisture and a raid gate are available for germination. These conditions allow the fungus to develop and it’s quick life cycle and demands for regular fungicide use can increase the risk of resistance. Fortunately, in a glasshouse environment we can influence the climate itself, which also means we can have an impact on the development of Botrytis. Climate management alone can only reduce pressure and careful attention is required as it can have disastrous consequences for the crop.

Botrytis is defined as a high-risk fungal pathogen for resistance. To avoid resistance development, it is important to alternate between the right products. It’s also important to consider which mode of action the product has. The overview below indicates the FRAC codes for products. It’s important to alternate between products with the different codes to avoid resistance development. Alternating FRAC codes can help avoid resistance; more information can be found on

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