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Flat scarlet mite – additional information

Life cycle

Flat scarlet mite is a relatively sedentary pest which tends to live in groups.

  • It overwinters as fertilised females on the bark of apple.
  • They become active in early spring, from April onwards, and invade the foliage and flower/fruit clusters in May.
  • The first eggs are laid on the wood late in April but subsequently eggs are laid along the midrib, beneath the leaf hairs. Eggs hatch from late June onwards.
  • Mating takes place in August and September.
  • The males die and fertilised females migrate to the bark where they overwinter.
  • There is one generation per year.

Pest status

Flat scarlet mite is a minor pest of apple and sometimes pear of increasing importance in the UK.

Other hosts

Scarlet flat mite has also been recorded as a pest of plum and walnut in the UK and Europe and is known as a pest of quince in Egypt and Turkey.

Varietal susceptibility

Apple varieties vary considerably in their susceptibility to flat scarlet mite. Cox is the most susceptible variety commonly grown.

Distribution

Common and widely distributed and present at least at low levels in most apple orchards.

Recognition

Adult female
Up to 0.32mm long; bright red and flattened; legs very short.

Adult male
Similar to female, but smaller and paler in colour.

Egg
0.11 x 0.07 mm; bright red and oval.

Monitoring

Overwintering populations
Overwintering populations of females can be counted in winter. High numbers indicate high populations were present the previous season and present a threat for the following season.

In summer
The foliage of trees should be inspected for infestation or signs of damage from May onwards, looking out for eggs or mites on the undersides of leaves along the midrib and for characteristic damage.

Forecasting

Forecasting methods for flat scarlet mite suitable for use by growers have not been developed.

Biological control

FAST has recently demonstrated that some control of flat scarlet mite can be made by introductions of predatory mites supplied by biocontrol companies, including Physoseiulus persimilis and Amblseius sp.  However, the level of control was limited and the cost very high.

Natural enemies

Predatory mites
Several species of predatory mite in the family Phytoseidae prey on flat tree scarlet mite, including Typhlodromus pyri, the species which occurs in selectively sprayed apple orchards and is the key natural enemy of fruit tree red spider mite and apple rust mite because it has developed resistance to organophosphorus insecticides.

  • 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.
  • Typhlodromus pyri also appears to have a regulatory influence on populations of flat scarlet mite, though it does not seem able to give sufficient natural regulatory control to prevent serious outbreaks of flat scarlet mite.

Other predators

Flat scarlet mite is preyed on by several other generalist insect and mite predators such as anthocorids, mirids and spiders.

Biotechnological control

Biotechnological control methods have not been developed for flat scarlet mite.

Further reading

Jeppson, L. Keifer, H. & Baker, E. (Eds)1975. Mites Injurious to Economic Plants. University of California Press, 273pp, 281pp.