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 bark of apple trees should be examined in the dormant period (early on if a tar oil winter wash treatment is to be applied) for signs of infestation.
Monitoring crawler emergence
- Correct timing of insecticide sprays for control is important and should be determined by regular monitoring.
- Weekly examination of mother scales and the surface of the bark on dry days though the critical period is required.
- Alternatively, the branches of infested trees may be furnished with sticky bands made from double sided clear sticky tape (see image) and the numbers of crawlers captured counted.
- The bands should be refreshed each week.
- By this method it is possible to ascertain when approximately 80-90% of scales have emerged, the critical time for application of first sprays.