The assessment of the risk of Ink disease and the evaluation of the efficacy of control measures need a quantitative and qualitative monitoring of Phytophthora cambivora inoculum in soil and host tissues. Diagnostic methods based on isolation on pure culture are time consuming and poorly sensible. However DNA based detection methods do not provide information on viability of the inoculum. Viability in biological samples can be evaluated using RNA transcripts rapidly degraded in dead cells. In this study the possibility to utilise mRNA transcripts of cytochrome oxidase II gene (Cox II) as marker of viability of Phytophthora cambivora was investigated in vitro following treatment with potential physical and chemical inductors. Cox II transcripts are detectable in Real-Time RT-PCR and their expression increased up to 6 times following treatment with glucose, KNO3 and K3PO 3.