Use of Phosphite Preparations to Protect Ash Seedlings Fraxinus excelsior L. against Phytophthora spp. and Hymenoscyphus fraxineus Pathogens

Abstract

In this study, greenhouse tests were conducted on 240 Fraxinus excelsior seedlings to investigate the simultaneous damage caused by thea pathogenic fungus and oomycetes. The experiment was performed under controlled conditions in the greenhouse of the Institute of Forest Research in Sękocin Stary (Poland). Three species of oomycetes were used for the experiment: Phytophthora plurivora, Phytophthora taxon hungarica, Phytophthora megasperma, and the fungus Hymenoscyphus fraxineus. Inoculations using the fungus were carried out on shoots and in plant pots in which the soil was mixed with the three Phytophthora species mentioned above, both simultaneously and separately, which made it possible to recognize the cumulative effect of the related plant infection. The aim of the study was to investigate the effect of phosphite-containing preparations on the health of common ash under conditions of threat to the roots by Phytophthora spp. and damage to the aerial parts of the plant by the fungus, as well as the possible occurrence of synergistic effects. Two types of protective preparations (Actifos and Phos60 of the nitrogen and potassium forms, respectively) were used. It was found that the inoculation of ash seedlings with the fungus H. fraxineus resulted in plant mortality, while the mixture of Phytophthora did not cause significant damage. It was confirmed that when pathogens coexist, a phenomenon occurs that leads to an acceleration in the development of disease symptoms and, thus, to plant mortality. In vitro tests confirmed the usefulness of phosphite preparations for the protection of ash seedlings.