Survival of <i>Pseudomonas syringae</i> pv <i>actinidiae</i> on the orchard floor over winter

Abstract

Pseudomonas syringae pv actinidiae (Psa) was first identified on kiwifruit (Actinidia spp) in New Zealand in November 2010 and has since caused serious losses particularly in Te Puke The role of fallen leaves and pruning debris in the lifecycle of Psa in New Zealand is unknown Survival of Psa was investigated in fallen leaves and cane prunings over winter 2011 Heavily infected leaves and cane prunings with Psa dieback symptoms were kept on the orchard floor and in the laboratory and assayed weekly for the presence of viable Psa At leaffall all leaves yielded live Psa Although detection frequency declined over time especially after 56 weeks Psa was still isolated from leaf litter 15 weeks after leaffall and cane prunings 11 weeks after winter pruning These results indicate that the pathogen overwinters readily in leaf litter and pruning debris representing a potential inoculum source for infection of new spring growth