Yes, one of infested orchards in Samara region is died together with FB after frost lower than -40oC. But it was observed ones only.

Nataliya, Thank you ! I have heard about disappearence of FB after natural colonization of trees by Pantoea agglomerans, but it was just an observation, not experiment. I know that P.agglomerans is a strong antagonist of Eamylovora, and can carry phages of Ea.

Last year we visited known outbreaks of Ea in Voronezh and Lipetsk regions for monitoring of FB situation. We observed more or less typical symptoms (not very strong) and collected the samples. But most of these samples demonstrated PCR-positive results and negative IF and isolation. However, I isolated several strains of Pa and Ps.s. (according sequensing with 8UA) from these samples. In the other hands, we observed situation in Khvalynsk (Saratov reg) when Ea could be detected on the same trees not every year. We also isolated Ps/s from these samples (but didn't see on Pa). I think, antogonists are important for FB epidemiology in our continental areas. If somebody interested I can collect Pa during my asseys.

Nataliya, thank you, I think that Pa can be very important part of infection cycle of several pathogenic bacteria. There is a report about Quorum Sensing molecules of Pa that rule by P. syringae bacteria, and that is explaining many facts of co-existance of Pa and Xanthomonas, Erwinia, Pseudomonas syringae and dominance of Pa at late stage of disease. If you can collect Pa from different sources we can start a project on this bacteria. We also have some strains, including one with sequenced genome.

In Slovenia we have some experience with eradication measures against Erwinia amylovora (Burr.) Winsl. et al. Slovenia was free from Erwinia amylovora (Ea) until 2001. The first single find happened in July 2001 on old pear tree. Eradication measures were applied by competent authority (Decision published in Official Journal). Two further positive samples were found within 1000 m focus based on official survey; infected trees were destroyed. All three finds were in private gardens within not an important fruit production area. Survey of 5 and 10 km buffer zone did not result in other finds.

But a low incidence of the disease was reported in 2002 in the north-west uplands of the Gorenjska region: new finds after surveys in area of first infestation in 2002, at Skofya Loka. Strict measures were applied again, but the disease nevertheless spread to 73 new foci in May-June 2003 due to very preferable conditions during the blossoming of host trees (manily quince and apple).

If we show these actions in numbers: In 2001 only 3 trees in extensive orchards were found positive at 1 location out of 791 monitoring locations all over the country. In 2002, the same location in Naklo and a second one in a 1 km radius were found positive, whilst 875 other monitoring locations were fireblight free. Despite strict quarantine measures implemented after discovery in the first focus, the bacteria spread in 2003 to the entire Gorenjska region and a further spread towards eastern and southern Slovenia was recorded. The plant protection service registered 184 new foci by the end of the season 2003 in Gorenjska. Twenty-three foci were scattered in other regions. Quarantine measures were imposed in every focus with destruction of infected plants. It was assumed that the spread of the bacteria was principally enabled by favourable weather conditions, the presence of the inoculum and intensive bee hive movement from Gorenjska region, which resulted in ascertained blossom infection. For more details you can see a reference: Knapic V, Potocnik A, Skerlavaj V, Brecl A (2004) Bulletin OEPP/EPPO Bulletin 34 (3), 351-356.

In 2004 Slovenia became the EU Memeber State and had received an European Union Protected Zone status for Erwinia amylovora. Based on data obtained from annual monitoring results since 1998 with permanent monitoring points Slovenia maintained the protected zone status (PZ) also after first outbreaks. Since 2001 delimited areas have been maintained in detailed maps. Many spatial analyses were made using GIS and registers available at the Ministry of agriculture, forestry and food (land units spatial data, central registers of farms and registers of fruit growers). Growers and general public were informed via web sites and media about curative and preventive measures. Some restrictions on ornamental host plants were imposed in fruit growing areas.

But since eradication in Slovenia in one part was not successful, it was concluded that Erwinia amylovora is present at low prevalence in some areas. These areas were excluded from protected zone, which remained free from Erwinia amylovora. In 2006 the disease did not spread: foci considered to be active since they were delimited less than 2 years ago. There was no positive findings - no infected host plants in Slovenia in 2006. Delimitation of foci and infested areas can be seen at archive web sites:

Situation 2006/2007: http://www.furs.si/en/zvr/hr_ozig.asp (areas, where Erwinia a. had established in yellow, foci in red.)

Situation in 2012: http://www.arhiv.fu.gov.si/en/services_and_measures/regulated_organisms/bacterial_fire_blight_erwinia_amylovora/index.html

Current situation): http://www.uvhvvr.gov.si/si/delovna_podrocja/zdravje_rastlin/posebno_nadzorovani_organizmi/hrusev_ozig/

In 2014 Slovenia has still kept its protected zone status for Erwinia amylovora in the part of territory, where eradication of first finds was succesful. From protected zone are excluded areas with low prevalence of infection: the regions Gorenjska, Koroška, Maribor and Notranjska and the municipalities Renče-Vogrsko (south from the highway H4) and Lendava.

I hope this is useful. Best regards,

Vlasta

The experience since more than 100 years of research on fireblight (described in several books and papers since the first report from Thomas Burril in the USA) is that once the disease is present in an area/orchard the only effective measures of control are based on eradication. All methods available (antibiotics (not in EU), copper compounds, biological control agents, etc.) do not eliminate the inoculum. In Europe the disease is of quarantine. During the first outbreaks of the disease it is extremely important that growers and Administration work together for an active program of detection and eradication of foci. In Spain thanks to this strategy we have delayed the spread of the disease to all apple&pear areas from 1995 to 2013 (almost 18 years), but unfortunately now it is present in all pomefruit growing areas. The same experience in Italy since 1993. Take into account that under favorable conditions (susceptible host and tissues, aggressive E. amylovora strain, and weather conditions) the minimal infective dose of E. amylovora is near to 10-100 CFU, that in many cases is undetectable for the most efficient methods of analysis (enrichment ELISa or rtPCR). Take also into account the possibility of having assimptomatic plant material, but still contaminates (may happens in nursery plant materials). You can find some information in my Researchgate page, in several papers.

@Vlasta, thank you. Your information looks similar to our findings.

@Emilio, thanks, we have near the starting point of Erwinia amylovora epidemics, so, we can try all ways to cure the disease

@Emilio, Hi!

I'm not sure I agree with your minimal infective dose. We regularly detect more bacteria and we don't always have disease. I agree that when all is right: bacteria present, weather conducive and susceptible cultivars, then things move fast!

As you know, in America we "live" with fire blight (FB). Eradication is not an option. The key is management: Copper in early Spring, antibiotics (or blossom protect) when conditions are favorable during bloom, removal of flowers in new blocks, Apogee before petal fall in some blocks and pruning out symptoms as soon as they appear. When efforts are concentrated in the most susceptible blocks =

Thank you everybody!

I have much hope on establishement of Pantoea agglomerans popuations that can be antagonist and carry Ea-specific phage as well. Anyway, in Russian climate fire blight speading slower than we could expect.

Hi Alex,

Just saw this thread.  Just wanted to check in with your approach...I agree that Pantoeas can be effective biological control agents and reduce the disease incidence, but they will not eradicate Erwinia amylovora.   Also, you will need to spray or apply high populations of the Pantoea spp during mid bloom every year to protect opening flowers from colonization and infection by the pathogen.  We have worked with Pantoeas for fire blight control in field trials at experimental orchards for ~20 years.  The bacterium colonizes flowers well and can be detected on the calyx end of mature fruit.  Yet, the next year, we do not detect the bacterium on newly opened flowers on non-treated trees using conventional methods (plating).  So, even if Pantoea is established as a resident bacterium in an orchard, it is unlikely to disperse and colonize (protect) the majority of newly opened flowers when vectored by natural methods (bees, insects, wind, and rain)....so annual applications during bloom are needed to establish the pantoeas on flowers at populations for significant suppression of Erwinia amylovora. 

Good luck with your research...I look forward to hearing about your progress!

@Virginia, sorry for late reply: we have found the same as you have described, but it was natural Pantoea population. Erwinia is a new pathogen for Russia, it is spreading across European part of the coutry for last 3-4 years. I hope, it will be not so competitive as in USA.