An indirect dot immunobinding assay (DIBA) with a PAb raised against an isolate of P. cinnumomi was evaluated to detect Phytophthora spp. in naturally dark-rooted woody plants. Screening of different modifications of the procedure were done with root samples of Chamaecyparis lawsoniana non-infected and infected with P. cinnamomi. With the optimised DIBA procedure, root infection could be diagnosed by a clearly defined halo around the spot and by a colour change in the spot using Fast Red or Fast Blue substrate. Detection of different Phytophthora species in Chamaecyparis plants from commercial nurseries was successful with the optimised procedure.