This tree is on fire: a review on the ecology of Erwinia amylovora, the causal agent of fire blight disease

Fire blight represents a great threat to apple and pear production worldwide. The ability of its causal agent, Erwinia amylovora, to spread rapidly in the host plants makes this devastating disease difficult to manage. Copper and antibiotics are still the most effective solutions to control fire blight, although their application contribute to environmental pollution and to the development of E. amylovora resistant populations. Thus, there is an urgent need to find new alternatives to such plant protection products. In this review, we summarized what is known on E. amylovora biology, as the knowledge of the plant pathogen biology is essential to develop eco-friendly management strategies. Notably, the presence of E. amylovora alone does not necessarily result in the disease development as it is the final outcome of multiple interactions established between E. amylovora cells, flower microbiota, plant host, insect vectors and environment. For instance, specific humidity and temperature create the suitable conditions for E. amylovora to grow and reach the specific cell density needed for plant infection. Once fire blight develops, insects act as potential vectors of E. amylovora, playing a role in the dispersal of the disease. The host plant represents an important factor as its susceptibility varies among the species belonging to the Rosaceae family. Recent studies showed apple flower microbiota might promote or hinder the infection progress, thus representing a possible source of new biocontrol agents effective in controlling E. amylovora.