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Recognition (Mussel scale)

Adults 2.0-3.5 mm long, flat and mussel–shaped, grey to yellowish brown. Found on the bark and fruits of apple trees. Nymphs (crawlers) Oval, pale yellowish brown.             Eggs Minute, oval and white. Deposited beneath the scale. Other pests with …

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Damage (Mussel scale)

The main damage is caused by the presence of mussel scales on the surface of fruits at harvest. The contamination is superficial but may downgrade the fruit. Very heavy infestations on the bark may debilitate the tree and there may be some contamination …

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Monitoring (Mussel scale)

Visual inspection Record the percentage of fruits at harvest contaminated by mussel scale. If the level is economically significant (e.g. >1%), then insecticidal treatment may be justified in the dormant period or after blossom the following year. The …

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Forecasting (Mussel scale)

A mass hatch of the eggs of mussel scale often occurs in a short time period of a few days in late May or June. Insecticide sprays need to be targeted against the young crawlers that emerge. Mature larvae are protected by their outer scale and are much …

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Chemical control (Mussel scale)

Correct timing of insecticide sprays for control is important and should be determined by regular monitoring (see ‘ Monitoring ’). It is a common error that sprays are applied too early. Eggs in shaded places hatch well after those exposed to the sun. …

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Cultural control (Mussel scale)

There are few obvious cultural control measures for this pest. Isolation from hawthorn and other trees that are wild hosts will reduce the probability of infestation developing. Mussel scale populations tend to be greatest in old orchards where the pest …

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Natural enemies (Mussel scale)

Scale insect populations are host to a complex of natural enemies. Parasitic wasps The minute chalcid wasp Aphytis mytilaspidis is a common external parasite of mussel, oyster and pear scales. The egg of the parasite, usually one per scale, is laid under …

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Biological control (Mussel scale)

Biological control of mussel scale has not been developed. However, the parasitic wasp Encarsia perniciosi has been introduced to control the San José scale with some success in other European …

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Further reading (Mussel scale)

Ben-Dov, Y. & Hodgson, C. J. 1997. World Crop Pests, Volume 7B. Soft Scale Insects – Their Biology, Natural Enemies and Control. Amsterdam, Elsevier. Helsen, H. H. M., Blommers, L. H. M. & Trapman, M. C. 1996. Timing observation and control of mussel …

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