Traditional methods of insecticide application are effective but inefficient. Often, fractions of the amount applied are required to achieve the desired biological response. Inefficient use of insecticides can give rise to unwanted side-effects including detrimental effects on populations of beneficial arthropods which have been shown to play an important role in the prevention of pest outbreaks in some years. The degree of short term residual exposure that a non-target arthropod receives from an insecticide application depends on the distribution of insecticide and non-target species within the canopy. Direct contact with insecticide spray is also an important route of exposure and this is dependent on the physical spray characteristics and the degree of protection that the organism receives from the canopy. Despite distributions and physical spray characterisations from a variety of agrochemical spray application nozzles flat fan nozzles and a spinning disc were quantified within a mature winter wheat crop canopy and an artificial crop. In addition, the effect of changing droplet size spectra on direct spray capture by a variety of beneficial anthropods was studied. This data was used in conjunction with existing susceptibility indices for beneficial arthropod species subjected to different insecticide applications at different timings. The derived indices for seven important beneficial arthropod species indicated that insecticides applied using traditional hydraulic nozzles posed more of a risk to the majority of important beneficial arthropods than an alternative representative, the spinning disc application system. This was tested in a field situation and results showed agreement with the indices derived from the model. The importance and possible uses of the susceptibility model within Integrated Pest Management systems is discussed with emphasis on areas where the model may help identify spraying systems which can be used to reduce insecticide output and optimise spray placement in crop canopies.