Pest and disease incidence of Ulmus sp. in forest shelter belts along the Kyiv–Kharkiv highway

Abstract

Introduction

Starting from the 1960s, Ulmus sp. trees in many regions were significantly affected by Dutch elm disease (DED). Publications indicate that the species composition of Ulmus sp. varies with longitude as well as their requirements for ecological conditions. We hypothesized that the susceptibility of elm species to biotic damage also depends on the geographical location of the stands. Therefore, our research was started in the forest protection belt along the highway from Kyiv to Kharkiv, where three Ulmus species with various types of damage are widely represented.

The research aimed to assess the infestation of different Ulmus species by bacteriosis, Dutch elm disease, butt rots, and bark beetles in the fragments of the Kyiv – Kharkiv highway within individual administrative regions.

Materials and Methods

In June – September 2023, 2,250 trees of the genus Ulmus were examined in 96 test plots in forest belts along the M 03 highway, passing from the West to the East through the territory of Kyiv, Poltava, and Kharkiv regions. The sample plots were located at the parts of the shelter belt with the dominance of one or several Ulmus species, particularly U. glabra Huds., U. laevis Pall. and/or U. pumila L.

The infestation type for each inspected tree was identified by visual signs. The pathogens of DED were identified from symptomatic shoots using mycological methods (incubation on Malt Extract Agar, Biolife Italiana) as well as using primers ITS PCR ITS1-F та ITS4. Species-specific primers mtsr1 (5?-AGTGGTGTACAGGTGAG-?3) and mtsr2 (5?-CGAGTGGTTAGTACAATCC-?3) were used for differentiation O. ulmi and O. novo-ulmi. For identification Ophiostoma novo-ulmi and its hybrids or subspecies, specific primers for gens col1 (SSPP) and cu (CU1 і CU2) were used.

The incidence of each cause of elm damage was estimated as the proportion of trees with certain symptoms or signs from the total amount of inspected trees (for each Ulmus sp. or stand fragment).

Results and Conclusions

The part of U. glabra decreased from Kyiv to Kharkiv regions. U. laevis was more represented in Poltava region while U. pumila was in Kharkiv region. The main factors for the weakening of elms were bacteriosis (on average 10.6–13.4 % of trees) and DED (4–10.2% of trees), to a lesser extent – butt rot (2.5–4.5 % of trees). Within the observable height of the trunks, bark beetle exit holes and galleries were found on 4.5–9.9 % of trees. The proportion of damaged trees depended on elm species and the location of shelter belt fragments. U. pumila was the most affected with 47.2, 32 and 33 % of trees with the presence of different types of damage in the fragments of shelter belt within Kyiv, Poltava, and Kharkiv regions, respectively, including 11.3; 10.7 and 9.3%, respectively, particularly affected by DED. For the first time in the study region, the presence of Ophiostoma novo-ulmi subsp. americana and its aggressive hybrid Ophiostoma novo-ulmi subsp. americana ? novo-ulmi (pathogens of DED) was confirmed by molecular methods. Bacteriosis of all elm species was most widespread in a fragment of shelter belt within Kyiv region, and least widespread within Kharkiv region.

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