The influence of the spray program on the natural control of oystershell scale, Lepidosaphes ulmi (L.).

The control of apple pests In Nova Scotia has developed into an arduous and expensive process [...] The study of the effects of the spray program on the natural control of oystershell scale which forms the basis of this thesis is in turn a part of the whole general ecological approach to the study of orchard pests in Nova Scotia. During the course of these experiments it became very evident that time and space are two very important factors to be considered in the investigation of orchard insect problems. The spray program which has been followed in an orchard in the years before an experiment is started has an important conditioning effect on the experiment. This can only be overcome by using the experimental materials on the same trees for several years in succession. Single row plots are limited in long term studies by the differential ability of the various species to migrate from one plot to another. The importance of the failure to consider the over-all effect of a spray program is illustrated by the advocation of elemental sulphur sprays for commercial orchards on the sole basis of their fungicidal value without relation to their effects on all other organisms As a result of these investigations it is now known that sulphur sprays inhibit natural control of oystershell scale while bordeaux mixture, Fermate or no spray at all will allow natural control agents to eliminate oystershell scale