Botrytis rot is one of the most common causes of rotting in stored apples and can cause significant losses. The fungus readily develops at storage temperatures and forms large nests of rots in long-term stored fruit.
Botrytis fruit rot
The symptoms are variable depending on the variety and the source of infection.
Botrytis rot associated with wounds is regular in shape, firmish, pale-mid brown in colour often with darker areas around the calyx and lenticels.
Botrytis rot associated with calyx infections varies in colour from pale-dark brown and is irregular in shape, often appearing as fingers of rot extending down from the calyx.
The disease cycle and epidemiology involves spores (conidia) being spread by wind and rain at any time of the year.
Inoculum sources of B. cinerea in the orchard are ubiquitous and virtually impossible to eliminate. Spores are produced from these during wet weather throughout the year and colonise dying flower parts during bloom.
These infections either develop into dry-eye rot visible in the orchard or remain as latent infection and subsequently develop in store.
Botrytis eye rot
The risk of botrytis eye rot in store can be assessed pre-harvest from previous orchard rot history and from the rainfall incidence between June and harvest. Where a high risk of eye rot has been determined, schedule the fruit for earlier marketing to minimise losses in store.
- Fungicide treatments applied during bloom have no effect on control of Botrytis eye rot.
- Control of Botrytis rot from wound infections requires an integrated approach based on cultural measures including packhouse, yard and bin hygiene, ensuring that pickers are well supervised at harvest to avoid fruit damage.
- A pre-harvest spray of the fungicides Bellis (pyraclostrobin + boscalid) or Switch (cyprodinil + fludioxonil) will give some control.
- In organic orchards, rot risk assessment can be used to assess the risk of eye rot and minimise losses in store where a high risk has been identified by marketing the fruit early.
- Control of Botrytis wound rot in stored apples is dependent on cultural measures of control.
rot in store may either arise as a wound infection or as an eye end rot arising from infection that occurred during blossom and later developed in store.