Dieback of small-leaved lime trees (Tilia cordata Mill.) caused by Gibsiella quercinecans in urban areas in Poland

In the summer of 2023, small-leaved lime trees (Tilia cordata) in the capital city of Warsaw were found to be dying along transport routes. The stem fragments collected for analysis showed the presence of necrosis near larval galleries caused by Agrilus viridis (L.). After a detailed microbiological analysis of both the tissues taken directly from the necroses and from the larval galleries, the presence of five different bacteria was confirmed, including Gibsiella quercinecans, which is responsible for the phenomenon of oak stand dieback known as Acute Oak Dieback. The pathogenicity tests carried out confirmed that this bacterium is also capable of causing necrosis on lime trees. The fact that this bacterium was found in the larval galleries of the polyphagous A. viridis could also indicate that it was vectored into the lime tree from other species, for example, oaks. The results obtained are the first report on the occurrence of G. quercinecans on lime trees in Poland.