Scale insects are serious pests of tree fruits in Ontario. Numerous species exist in Ontario including the Oystershell scale Lepidosaphes ulmi (Linn.), Lecanium scale Lecanium sp., San Jose scale (SJS) Quadraspidiotus perniciosus (Comstock) and the European Fruit scale (EFS) Q. ostreaeformis (Curtis) along with many other minor scale species. In Ontario, SJS and EFS are the most serious scale pests with both species found in all regions of the province in recent years. Each species is capable of causing direct injury to the fruit and/or injuring the host tree by sap feeding thus reducing tree vigour and possibly causing death of limbs. Records from the early part of the century revealed that high numbers of scale insects were a cause of tree mortality on tender fruit crops (peaches, nectarines, plums and cherries).
Although the type of injury caused by 515 and SJS is similar, the biology and the ability to reproduce differs between the species making effective control decisions important.