Relative significance of nursery infections and orchard inoculum in the development and spread of apple canker (Nectria galligena) in young orchardsA. R. McCracken; A. Berrie; D. J. Barbara; T. Locke; L. R. Cooke; K. Phelps; T. R. Swinburne; A. E. Brown; B. Ellerker; S. R. H. Langrell · 2003