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Apple sucker – additional information

Life cycle

There is one generation per year. Apple sucker overwinters in the egg stage. The eggs are straw coloured and are found on the bark mainly on the fruit spurs generally along leaf scars.

  • Egg hatch begins in late March or April at bud-burst of Cox and Bramley and is complete by green cluster.
  • The newly hatched nymphs are orange brown with red eyes. They invade the bursting buds and blossom trusses feeding on the green tissue.
  • Drops of honeydew and conspicuous white or irridescent waxy threads are secreted by the nymphs and these are visible in infested trusses. No sooty mould is associated with the honeydew.
  • After a second moult, the nymphs become bright green and develop wing buds.
  • Feeding continues and after 4-6 weeks the first adults appear.
  • The adults live and feed on apple throughout the summer and early autumn.
  • Egg laying begins towards the end of August and continues for about one month. The adults then die.

Pest status

Apple sucker was once a serious pest of apple but nowadays it is well controlled by insecticides, except in organic orchards and in some cider orchards.

Other hosts

Apple sucker lives only on apple.

Varietal susceptibility

There are considerable differences in the susceptibility of varieties. Lord Lambourne and some cider varieties are highly susceptible.

Distribution

Widely distributed and common.

Recognition

Eggs
0.4 mm long, elongate oval and creamish yellow. Found on the bark of young branches and shoots, mainly around spurs and leaf buds (very similar to pear sucker eggs).

Nymphs
Apple green with red eyes, body flattened, broad and ovate, with conspicuous wing buds in later instars. Found mainly in flower trusses at the base where flower stalks meet in spring. Honey dew blobs and waxen threads betray their presence.

Adults
2.5-3.0 mm long, apple green to yellow. Wings transparent with green veins.

Monitoring

The presence of large numbers of overwintering eggs round the spurs will warn that an attack by apple sucker is likely.

  • Levels of apple sucker should be assessed as part of the normal pre-blossom pest assessment at the green cluster growth stage (see section ‘Pest and disease assessment’).
  • Ideally carefully inspect 4 trusses on each of 25 trees per orchard.
  • Look out for the characteristic blobs of honey dew and wax at the base of the flower stalks. The suckers themselves can be rather difficult to see because they are a similar colour to the leaf.
  • Treatment is justified if more than 30% of trusses are infested.

Forecasting

Forecasting methods for apple sucker have not been developed.

Chemical control

A spray of an approved insecticide should be applied if damaging infestations occur in spring.

  • The synthetic pyrethroid insecticide deltamethrin (Decis) is recommended for control of suckers on apple, but the use of this class of insecticide should be avoided if at all possible as they are harmful to the orchard predatory mite, Typhlodromus pyri, as well as a wide range of other natural enemies.

Insecticide resistance

Apple sucker has not developed resistance to insecticides. However, pear sucker has developed resistance to a wide range of insecticides including carbamate, pyrethroid and insect growth regulator compounds.

Cultural control

Apple sucker is most troublesome in older orchards and on certain varieties. Avoiding these circumstances will reduce the problem.

  • It is possible that reducing the nitrogen status of apple trees will lead to a reduction in apple sucker problems.
  • This approach has been shown to be effective for pear sucker control. However, pear sucker feeds in the growing shoots and has several generations per year.

Natural enemies

Natural enemies, especially predatory flower bugs (anthocorids), should be fostered by avoiding the use of broad-spectrum insecticides

  • Predatory bugs are the most important natural enemies of apple and pear sucker.
  • Predatory flower bugs (anthocorids) are the commonest species but mirids such as Atractotomus mali are can also be important especially on young trees.
  • The predatory bugs feed mainly on eggs and nymphs and can be important natural regulating factors if populations are not harmed by the use of broad-spectrum insecticides.

Biological control

Biological control approaches have not been developed for apple sucker.

 

Further reading

Jonnsson, N. 1983. The life history of Psylla mali Schmidberger (Hom., Psyllidae); and its relationship to the development of the apple blossom. Fauna Norvegica B, 30: 1, 3-8.