Botrytis is a very common fungal disease found among a wide variety of plants. It tends to target wounded plants, but can also affect healthy plants in humid conditions. The species Botrytis paeoniae specifically targets plants in the genus Paeonia, commonly known as Peonies. It is present all year round and most active during spring and early summer, it can quickly destroy a healthy garden due to it's quick spread.
Fuzzy grey mould, brown leaf patches, flowers fail to open.
Environmental conditions like low temperatures, high humidity and hard-handling of plants are all condusive to this problem. The wetter your Peonies, the more susceptible they are to becoming infected. Furthermore, standing water on plant leaf surfaces provides the ideal place for spores to germinate.
Fuzzy grey mould on affected areas
Irregular brown patches on leaves and stems
Flower buds may fail to open
Remove infected plants and destroy them to reduce contamination and spread of spores. Prune or stake plants to improve air circulation. Treat with a biological fungicide.
The Botrytis fungus overwinters on plants, in or on the soil, and as sclerotia. Spores develop when conditions are optimal, and are moved by wind or splashing water onto blossoms or young leaves, where they germinate and enter the plant. Cool temperatures and high humidity are required for spores to germinate and spores will rarely penetrate healthy tissue directly. They prefer to enter through damaged areas, wounds or even cuttings.
Prevention is the best approach, this starts with controlling your environment. Handle plants with care and make sure not to damage them. Ensure good air circulation by allowing enough space between plants and thinning out vegetation for adequate air flow. Avoid overhead-watering, overwatering and watering late in the afternoon. Good hygiene and sanitation in the garden is very important and enforce this by removing any dead leaves and debris and by sterilising your equipment often.