Crown rot
For crown rot, most damage is already done by the time foliar symptoms are evident. Therefore, corrective treatments are not usually worthwhile.
- For crown rot, trees showing foliar symptoms are usually too badly damaged to save. These should be grubbed and burnt.
- The replanted tree and the trees in the rest of the orchard can be treated with a copper product or the chemical fungicide Fubol Gold WG (mancozeb + metalaxyl). At the time of up-dating this information in January 2024, copper was not approved for use on apple, but various products have been authorised for use as 'emergency authorisations' in the past, so growers and agronomists should continually check the latest status of copper products.
- Fubol Gold should be applied post harvest but before green cluster stage.
Collar rot
- Where collar rot lesions are not too advanced, control can be achieved by cutting out all bark in the affected area, including at least 5 cm of healthy tissue to expose the sapwood.
- The cut area must also extend through the graft union.
- Alternatively, to save labour, a groove is cut down to the sapwood in the healthy tissue around the lesion, so it surrounds the lesion and extends through the graft union.
- Physical acting products such as BlocCade when applied to pruning wounds or cut surfaces can help to protect against further infection by fungi such as Phytophthoras. To be effective, the wounds must be treated immediately after pruning.
- Applying fungicides as a trunk spray or to the orchard floor is ineffective.