TIMING OBSERVATION AND CONTROL OF MUSSEL SCALE LEPIDOSAPHES ULMI.

The mussel scale Lepidosaphes ulmi (L.) is locally an important pest in apple and pear orchards. Even light infestations can cause severe economic loss due to a zero tolerance on fruits for export. The optimal moment for chemical control is when all crawlers have emerged from under the scales. A temperature sum model was developed to indicate the best moment for observation and subsequent control.