The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy.
Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2, and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. In field experiments, after 1–2 apple tree injections of either streptomycin, potassium phosphites (PH), or acibenzolar- S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. 2Applied Insecticide Toxicology Laboratory, Department of Entomology, Michigan State University, East Lansing, MI, USA.1Tree Fruit Pathology Laboratory, Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA.For efficient monitoring and early detection of the pathogen, fast and on-site detection methods such as loop-mediated isothermal amplification (LAMP) PCR and AgriStrip® kit have been introduced and are currently being used in the field.Srđan G. Probably due to these aggressive management actions, the disease incidence rate could be reduced. Moreover, intensive chemical treatment and monitoring of fire blight have been performed. The South Korean government set up a management strategy for this disease in 2015, and recommended removing all trees within a 100 m radius range from an infected plant. In 2015, 43 orchards were confirmed to be infected by this pathogen, and 18 orchards were confirmed in 2016.
Based on several microbiological characteristics including genetic and biological assays, the disease was finally confirmed as fire blight disease caused by E. amylovora and was reported in Korea already in 1999, more careful analyses were required for confirmation of the fire blight pathogen. Because bacterial black shoot blight caused by Erwinia pyrifoliae has symptoms that are very similar to those of E. In 2015, fire blight-like symptoms were found in apple and pear orchards in three cities of Korea. Fire blight in apple and pear, caused by Erwinia amylovora, is very problematic worldwide and has recently been spreading toward East Asia from Europe.
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