Physical methods
Organic growers are sometimes forced to physically destroy colonies to prevent them spreading.
- This is sometimes done when hand-thinning fruitlets.
- This is very labour intensive and small colonies are often missed which flare up subsequently.
Fostering natural enemies
The main cultural control approach is to foster populations of natural enemies, especially predators (see below). This can be done in several ways.
- Tolerating less harmful aphid species such as the apple grass aphid attracts predators in early spring.
- Flowering plants (e.g. corn marigold, corn camomile and mayweed) can be established in or around the orchard to provide alternative food sources, mainly nectar and pollen, for adult hover flies.
- These may then lay their eggs in aphid colonies.
- Ground herbage under the tree may also become infested with other aphid species (e.g. grasses can become infested with bird-cherry oat aphid) which can provide an alternate food source for aphid predators (e.g. ladybird adults and larvae) and parasites.
- Artificial refuges should be used to foster earwigs and other natural enemies such as lacewings.
- Ideally, a refuge should be provided in each tree. This may simply be some extra lengths of hollow tree tie round the stake.
- In orchards with high tree densities, it is likely to be impractical to provide more elaborate refuges such as half of a plastic drinks bottle containing a roll of corrugated cardboard.