In the orchard
Botrytis fruit rot is rarely seen in orchards as a rot. On apple it may be visible as dry-eye rot at the calyx end of the fruit.
- The symptoms range from a slight skin red blemish on one side of the calyx to a distinct one-sided rot which has dried and shrunk to form the typical dry-eye rot.
- The presence of such symptoms in the orchard usually bears no relationship to the subsequent incidence of Botrytis rot in store.
In store
On Cox the symptoms are very variable depending on the source of infection.
- Botrytis rot associated with wounds tends to be regular in shape, firmish, pale to mid-brown in colour, often with a darker area around the calyx and lenticels (some times reddish spots), giving the fruit a freckled appearance.
- Botrytis rot associated with calyx (eye) infection varies in colour from pale to dark brown and is irregular in shape, often appearing as fingers of rot extending down from the calyx.
- This irregular rotting serves to distinguish Botrytis from other causes of eye rots such as Nectria which are usually circular and sunken.
- Similar rotting may also originate from the stalk end or on the cheek, which may suggest a core rot origin.
On other apple varieties Botrytis rot is mainly mid-brown.
- Infected fruit initially remain moderately firm becoming softer with time.
- Mycelium with grey spore masses may be visible particularly on the calyx or around the wound.
- Once out of store, these spore masses become more abundant, and are a useful aid to identification.
- Very occasionally on apple, large black resting bodies (sclerotia) may be seen, particularly at the wound where the rot originated.
- Botrytis rot spreads in store by contact and nests of rot may therefore be visible in later stored fruit.