It may be caused by two Pseudomonas syringae pathogens. The stem canker phase is the most important, but the pathogens also cause leaf spots/shot-hole, bud death, shoot die-back and flower blights.
The aim of HDC project HNS 179 was to identify management options that will benefit bacterial canker control by targeting sources of inoculum on the nursery and examining practical approaches to disinfecting knives and secateurs.
Spray trials were done on two commercial nurseries and examined six treatments to rootstock stock hedges, bud wood mother plants and budded plant material. Spray applications were made in spring, summer and autumn.
The most consistent effects were obtained with Cuprokylt (copper fungicide) plus a wetter (Activator 90). The highest pathogen levels were noted in spring and summer so spraying needs to start in spring to keep disease levels in check.
Secateurs blades were contaminated with a standard amount of Pseudomonas before being disinfected with different products. They were then used to make cuts in an agar medium, disinfection efficiency being assessed on the number of cuts that subsequently had bacterial growth.
Long-dip treatments (30 seconds) using one per cent chlorine solution or Jet 5 gave very good control but were deemed too impractical for use in a field situation. The most practical control measure was iso-propanol impregnated wipes.
Horticultural Development Company
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