Potential approaches to ensure adiverse and abundant source of inoculum for a screening plot wouldbe to have permanent rows of moderately susceptible varieties tosupply a diverse source of inoculum, the use of infected pottedplants, infected leaves or inoculum sprays, by allowing the accumu lation of debris on which the fungus overwinters and/or keepingtrials for at least 3 years. The dispersal of the black spot conidiacould also be encouraged by the use of overhead irrigation. Thegeneral approach for active commercial rose breeders is to planttheir trials with no or a minimal spray program. Beyond this, littledirected effort is made to increase the inoculum levels althoughtheir trials generally contain susceptible cultivars and are fre-quently planted along side established trials with disease. To ensurethey get reliable ratings for resistance they do not rogue susceptiblecultivars and run the trial for 2–3 years. The best performing rosesare subsequently replanted in multiple sites to expose them to agreater range of pathogen diversity. Nevertheless, field screeningwill not distinguish the race(s) the plants are resistant to. This typeof screening can be done efficiently using a detached leaf screeningtechnique with specific races in the laboratory [36].