- 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 of the foliage with honeydew.
- At first, the upper surface of the leaves assumes a glistening, sticky appearance but it later becomes unsightly with the growth of sooty mould fungi on the honeydew.