Pear scab disease is the major fungal disease of pears caused by two distinct species of host-specific Venturia: V. nashicola is restricted to Asian pears (Pyrus bretschneideri, P. ussuriensis and P. pyrifolia), while V. pirina exclusively infects European pears (P. communis). The incompatible relationships between European pears and V. nashicola, and Asian pears and V. pirina, are considered to be governed by non-host resistance. However, while thought to be a more durable form of resistance, the multi-layered molecular mechanisms of non-host resistance are poorly understood. The Asian and European pear hosts have previously been crossed to produce Eurasian pears with varying degrees of resistance to both pear scab fungi, providing another layer to the study of non-host resistance in the Pyrus-Venturia pathosystem. This provides a unique opportunity to dissect the genetics of host-specificity and to understand host-pathogen co-evolution from the perspective of non-host resistance. Fluorescence phenotyping has been used to characterise responses to different isolates of V. pirina in European, Asian and Eurasian pears. The defence transcriptome of Eurasian pears in response to V. pirina is being investigated to understand the dynamics of the molecular mechanisms underlying non-host resistance. Furthermore, core effector candidates shared between V. nashicola and V. pirina have been investigated in the whole genome sequences to determine their role during infection and possible contribution to the host-specific nature of these pathogens. These core effector candidates may be useful in not only identifying durable resistance genes for molecular plant breeding, but also be useful targets for the specific and sensitive detection of the Asian pear scab pathogen, V. nashicola.