Survival of Erwinia amylovora on pears and on fruit containers in cold storage and outdoors

The survival of Erwinia amylovora during cold storage or in the open air might be a relevant factor in the spread of fire blight. Pear fruits, the wooden or plastic container surfaces and the packaging paper may be vehicles for the spread over short, medium and long distances associated with the marketing of fruit, the movement of bins and trays, and the disposal of packaging paper after storage. Survival in cold storage (-0.5°C) and/or in the open air of a rifampicin-resistant strain was studied on pears, bins, trays and packaging paper. The surfaces of highly standardised samples were contaminated with a bacterial suspension. The washing liquid was centrifuged and the final concentrate was quantitatively streaked on selective medium. Although it was no longer possible to isolate the bacteria from the pear skin after 24 hours, survival in the calycine cavity reached at least 101 days. Survival was (considerable) on oak (20–30 days) and poplar wood (40–60 days); maximum survival was estimated at 60–70 days and 70–80 days respectively. After 24 hours the bacteria could no longer be isolated from polyvinyl chloride. Survival on packaging paper was 14-24 days. The grey paper used to line the sides was less conducive to survival than that used for the bottom. The survival curves were calculated for each type of material. An estimation of phytosanitary risk periods for the transmission of Ea based on the critical time of survival is hypothesised.