Oystershell scale - summer and harvest monitoring for IFP and organic growers

Scale control must address two sources of the scale problem - the scale insects living in the orchard and the scale insects which arrive as immigrants each summer from shelter trees and other host plants. Spray thresholds for both spring and summer control are based principally on the results of the previous harvest, supplemented by summer monitoring where required. This must be combined with a shelter management programme to minimise the scale immigration problem. Oystershell scale is a pest only in the regions of Canterbury and Otago.
Monitoring method – The primary monitoring method is the assessment of scale (all species combined) on harvested fruit (1000 fruit sample from bins in field, or packhouse records). Where summer monitoring is required (see thresholds), 500 fruits per cultivar block (e.g. 25 from each of 20 trees) should be checked for scale (all species combined) with a x10 hand lens, paying special attention to the calyx. Summer scale sampling should be done in areas of the orchard thought to be most at risk from scale invasion - i.e. close to shelter belts and other plants which might be harbouring scale - and not spread throughout the blocks. Late varieties, such as 'Braeburn', have greater risk of late summer scale immigration than early varieties. Shelter and other host plants should be checked for scale infestations as part of the shelter management programme.

TIMING: The normal optimum timing of first summer monitoring and/or applying the first summer insecticide for scale control is as follows for the orchard or the shelter:

These dates provide a guide to the timing of summer monitoring/insecticides for scale control. Further information may be available in-season from monitoring of crawler release by researchers/advisors.