- Where a new orchard is planned, consideration should be given to choice of variety and if possible selecting a scab resistant or tolerant variety, or if this is not possible, then avoiding very susceptible varieties such as Gala.
- Select an orchard site with good air circulation and consider planting trees at wider spacing to encourage good air circulation so that trees dry more rapidly after rain.
- Similarly, consider tree pruning and training and possibly selecting tree shapes which promote good air circulation.
- Where existing orchards are converted to organic production, then careful consideration should be given to pruning and tree training to promote good air circulation to promote rapid drying of leaf and fruit surfaces and reduce the apple scab risk.
- Emphasis must also be placed on cultural approaches to control. This is mainly concerned with elimination of overwintering inoculum such as elimination of leaf litter and wood scab etc. as outlined previously.
- The use of urea is not permitted in organic production.
- Therefore, the emphasis must be on physical removal of leaves or on maceration of leaf litter to encourage rotting.
Fungicides acceptable in organic production may also be used in conjunction with the above.
- Such fungicides should be a last resort rather than the only method of control used.
- Currently in the UK, the use of sulphur fungicides is permitted for scab control. Sulphur is a protectant fungicide, only partially effective against scab, and therefore requires frequent applications to achieve control.
- Efficacy can be improved if applications are carefully timed with scab warnings.
- However, repeated applications of sulphur may initially interfere with management of phytophagous mites with T. pyri.
- The use of copper fungicides (check status of current authorisation) is at present permitted with restrictions in organic production, but may eventually be banned.
- Copper fungicide may be used prior to bud burst to control scab overwintering on the tree.
- Copper fungicides may be phytotoxic to young foliage and so should be used with caution.
In other countries, various ‘natural products’, either plant extracts or natural chemicals such as calcium hydroxide or kaolin (china clay) are reported to be effective alternatives for scab control.
- These products either act directly on the scab fungus in a similar way to conventional fungicides, or act on the plant to increase resistance to scab.
- Usually repeated applications are required to control scab.
- The scab control achieved has not always been successful.