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The fungus Neonectria ditissima causes European canker of apple To determine the pathogenicity of different isolates conidial inoculum of each isolate needs to be prepared Freezing inoculum ensures that conidia do not germinate before inoculation and facilitates screening of large numbers of isolates In this study conidial suspensions of three different isolates and field conidia collected from apple cankers were used to inoculate dormant potted 1yearold Royal Gala trees in a glasshouse Each conidial suspension were removed and inoculated with four replicates of two shoots per treatment Significant differences in disease incidence and lesion size were observed between the different isolates at each assessment date 5 to 15 weeks after inoculation (P

The European canker pathogen Neonectria ditissima can be transmitted by apple scion wood into newly developing trees following grafting or budding resulting in disease development and progression An in vitro hot water treatment showed that both conidia and mycelium of N ditissima can be killed when placed into water at 50C for 8805; 5 min However diseased scion wood required 8805; 15 min disinfection at the same temperature to eliminate all internal pathogens including N ditissima At this temperature and time duration no mycelium growth was observed after 2 weeks incubation of cut pieces of the disinfected tissues on apple sap amended water agar Although the treatment was 100 effective at eliminating some identified and nonspecific pathogens visual assessment of both the scion and rootstock viability and vigour six months after the hot water treatment showed that 98 of the rootstocks and scions failed to grow and develop

The fungus Neonectria ditissima causes European canker on apple and pear trees in temperate regions The thermal death point of ascospores and conidia of this pathogen is unknown In this study ascospores and conidia were exposed to six temperatures between 20C and 50C for seven time intervals between 5 min and 24 h The viability of the spore suspensions was determined by germination on slides and growth on potato dextrose agar Temperatures up to 30C did not reduce spore viability Exposure to 35C for 24 h reduced conidial and ascospore germination by 92 and 85 respectively At 40C and 45C spore viability was reduced after 5 min declining rapidly with increasing exposure times No spores germinated after 5 min at 50C This study suggests that 15 min dips in 45C water may kill surface spore contamination of budwood prior to grafting Budwoodbased validation studies are now recommended