Young trees from the nursery used to plant new orchards are often infested with apple rust mite and/or fruit tree red spider mite and do not have established populations of the orchard predatory mite Typhlodromus pyri.
- Damage by fruit tree red spider mite and often apple rust mite can occur rapidly in the first season after planting whereas the pest may be unimportant in other established orchards on the farm.
- Steps should be taken to ensure the nursery trees are not heavily infested with pest mites before they are purchased and delivered to the farm.
- In orchards, hot, dry situations favour rapid population increase of apple rust mite.
- Overall bare soil orchards should be avoided.
Natural enemies
The orchard predatory mite Typhlodromus pyri
- Several species of predatory mite in the family Phytoseidae prey on fruit tree red spider mite, but Typhlodromus pyri is the species which occurs in selectively sprayed apple orchards and is the key natural enemy of fruit tree red spider mite because it has developed resistance to organophosphorus insecticides.
- The predatory mite is also the key natural enemy of apple rust mite.
- If populations of the mite are conserved by avoiding the use of harmful insecticides, notably synthetic pyrethroids, fruit tree red spider mite and apple rust mite are seldom a problem.
Other predators
- Fruit tree red spider mite is preyed on by several other generalist insect and mite predators such as anthocorids, mirids and spiders and the stigmaeid mite Zetzellia mali.
Biological control
Establishment of the orchard predatory mite, Typhlodromus pyri, is crucial. Unless the predator is established, regular outbreaks of fruit tree red spider mite and apple rust mite are inevitable and these can be very damaging and difficult and costly to control.
- Once the predator is established and the biological equilibrium between the predatory mite and the pest mite has stabilised, fruit tree red spider mite and apple rust mite seldom cause problems, providing the equilibrium is not disturbed by the use of pesticides harmful to the predatory mite.
- The predatory mite will establish naturally in apple orchards but this can be a slow process.
- Pest mite infestations are present and can develop rapidly on newly planted trees which do not have established populations of the predatory mite (often because they have been sprayed with predator-harmful pesticides in the nursery).
- Where the orchard predatory mite is absent, e.g. in newly planted orchards, it should be introduced in summer by transferring extension shoots from established orchards where the predatory mite is abundant.
- Summer prunings may be used. Ideally, at least one shoot should be placed amongst the foliage in each tree of the orchard where the predator is to be introduced.
Biotechnological control
Biotechnological control methods have not been developed for fruit tree red spider mite.