Investigating Survival of Erwinia amylovora from Fire Blight-Diseased Apple and Pear Trees Buried in Soil as Control Measure

Abstract

BACKGROUND: Since 2015, fire blight disease caused by Erwinia amylovora has been devastating apple and pear orchards every year. To quickly block the disease spreading, infected apple and pear trees have been buried in soil. However, concern on the possibility of the pathogen survival urgently requires informative data on the buried host plants. Therefore, this study was conducted to investigate the survival of the pathogen from the buried host plants. METHODS AND RESULTS: Apple trees buried in 42 months ago in a Jecheon site and pear trees buried in 30 months ago in an Anseong site were excavated using an excavator. Plant samples were taken from stems and twigs of the excavated trees. The collected 120 samples were checked for rotting and used for bacterial isolation, using TSA, R2A, and E. amylovora selection media. The purely isolated bacteria were identified based on colony morphology and 16S rDNA sequences. Wood rotting and decay with off smells and discoloring were observed from the samples. A total of 17 genera and 48 species of bacteria were identified but E. amylovora was not detected. CONCLUSION: Our investigation suggests that the survival of E. amylovora doesn't seem possible in the infected hosts which have been buried in soil for at least 30 months. Therefore, the burial control can be considered as a safe method for fire blight disease.

Novel Detection Protocol for Erwinia amylovora in Orchard Soil after Removal of Infected Trees

“…To replant after the ban period, the soil must be confirmed to be free of E. amylovora. However, studies that confirm safety from re-infection through soil insects or soil containing surviving E. amylovora from removed infected host plants are lacking, and farmers continue to express anxiety and concerns about re-infection in their fields ( Kim et al, 2019 ).…”

Application of the Maryblyt Model for the Infection of Fire Blight on Apple Trees at Chungju, Jecheon, and Eumsung during 2015-2020

“…The first outbreak of fire blight in Korea was recorded in 2015 in apple and pear trees in Anseong, Gyeonggi-do; Cheonan, Chungcheongnam-do; and Jecheon, Chungcheongbuk-do ( Park et al, 2016 ). The areas affected by fire blight have expanded from 2015 to 2020 to include Chungcheongbuk-do (Chungju, Jecheon, Eumseong, and Jincheon), Gangwon-do (Pyeongchang), Gyeonggi-do (Anseong, Pyeongtaek, Yangju, Gwangju, Icheon, Paju, and Yeoncheon), Chungcheongnam-do (Asan, Cheonan), and Jeollabuk-do (Iksan), and they continue to expand rapidly ( Ham et al, 2020 ; Kim et al, 2019 ). In particular, 413.4 ha, which is 63.1% of the apple orchards in Chungju, Jecheon, and Eumseong in Chungcheongbuk-do were buried over the last 6 years, and 384.4 ha of those areas were buried in 2019–2020 due to a sharp increase in the incidence of fire blight.…”