Наукові праці Лісівничої академії наук України (Dec 2021)
Symptoms, prevalence and harmfulness of Fraxinus excelsior L. tuberculosis (pathogen - Pseudomonas syringae pv. savastanoi (Smith 1908) Young et al.)
Abstract
It should be noted that in recent years there has been observed a epiphytic dieback of many species of forest woody plants in Ukraine as well as in other countries, which is of dynamic nature and tends to grow. In the deep pathology of this phenomenon, phytopathogenic bacteria, which have a high reproductive energy and are able to penetrate into the plant from the outside and to cause a pathological process, are left out of consideration. It is found that the most common and harmful disease of common (European) ash is tuberculosis. The infection of common ash begins at an age of 2-3 years at the corresponding height of the trunk. Infection can be both exogenous and endogenous. The primary symptoms of tuberculosis (the so-called “scab”) appear on young trunks with a smooth (primary) grayish-green bark and are characterized by slight local swelling of the upper layer of cells, the appearance of microcracks, and small elliptical soft tumors filled with an odorless gray sticky bacterial mass. Tuberculosis causes more economic than environmental damage. Affected trees of older age groups die off relatively rarely, but as a result of a characteristic pathological process, wood is gets devalued. Affected trunks are usually cut down for firewood. Anatomical, morphological, cultural and physiological-biochemical studies were carried out at the Department of Phytopathogenic Bacteria, the D.K. Zabolotny Institute of Microbiology and Virology of the National Academy of Sciences of Ukraine. The bacteria Pseudomonas sp., P. fluorescens, P. syringae, Erwinia herbicola, E. horticola, Xanthomonas sp. and micromycetes Cladosporium cladosporiodes, Ulocladium botrytis, Mycelia sterilia (dark), Mycelia sterilia (orange), Fusarium sp., Acremonium strictum, Cylindrocarpon didymum etc. were isolated from tuberculosis pathology as an accompanying myco- and microbiota. It is shown that Xanthomonas sp. is found in the experiment variable pathogenic properties, which indicates the expansion of its specialization and indicates the need for further study of bacterial pathology of forest woody plants, In the pathogenesis of the disease, five stages (phases) of its development are distinguished and the main symptomatic characteristics of the lesions are given, which makes it possible to timely identify the affected tree for each age group of stands. The methods for diagnosing bacterial diseases of common ash have been improved. The species composition of the harmful entomofauna as a vector of infectious pathology has been determined. It has been shown that hydrothermal stress is a catalyzing factor for the epiphytotic dieback of common ash. It was revealed that there is a direct relationship between the spread of tuberculosis and the proportion of ash in the composition of stands of different age groups. In the research region, tuberculosis reaches epiphytotics on the coppice-originating trees of Fraxinus excelsior growing in dense stand, especially when they are young. It is shown that the pathology of common ash is a multifaceted phenomenon with interrelated processes of an infectious and non-infectious nature. The need to distinguish between the etiology and pathogenesis of this negative phenomenon is indicated, that is, one should not mix the factors that lead to the weakening of common ash (catalyzing factors) and the factors that cause epiphytotic dieback. For the purpose of preventing and reducing the general infectious background, systematic monitoring should be carried out in stands with the participation of Fraxinus excelsior to observe the cenotic optimum of ash in the composition of forest stands, to prevent thickening, to remove and dispose of young ground-ash tree affected by Pseudomonas syringae pv. savastanoi, and create favorable conditions for the growth and development of common ash.
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