Coleopterous predators of pine bark beetles in the last years of the outbreak recorded in Ukraine

Abstract

The purpose of this study was to identify the species composition of coleopterous predators and their occurrence in different parts of the stem depending on the health condition of Scots pine (Pinus sylvestris L.) in the collapsing foci of bark beetles (Coleoptera: Curculionidae: Scolytinae). The research was carried out in 2019–2021 at 38 sample plots located in five State Forestry Enterprises of Sumy region (Ukraine). All sample plots are located in pure Scots pine stands in relatively poor forest site conditions. The relative density of stocking is 0.6–0.7, and the age of stands is between 60 and 110 years. The health condition for each tree was evaluated on visual characteristics by the classes: first – healthy; second – weakened; third – severely weakened; fourth – drying up; fifth – recently died and sixth – died over a year ago. Bark beetles’ nuptial chambers and predators were counted on 25 × 25 cm pallets, which were located at the lower, middle and upper parts of the stem with thin, thick and transitional bark, respectively. The significance of differences in the performance of predator species depending on the tree part, health condition and year was analysed using the nonparametric Kruskal–Wallis (K–W) test. The species composition of predators in different years, stem parts and tree health condition was compared using the Sorensen–Chekanovsky index. In the collapsing foci of bark beetles, the health condition of Scots pine in 2019–2021 tended to worsen. The infestation density of Ips acuminatus (Gyllenhal, 1827) and Ips sexdentatus (Boerner, 1767) was 0.62 ± 0.032 and 0.64 ± 0.017 nuptial chambers per 1 dm2, respectively, and also decreased in 2019–2021. In the galleries of bark beetles, seven species of coleopterous predators were collected: Aulonium ruficorne (Olivier, 1790) (Zopheridae), Platysoma elongatum (Leach, 1817) (Histeridae), Rhizophagus depressus (Fabricius, 1792) (Monotomidae), Corticeus pini (Panzer, 1799) (Tenebrionidae), Thanasimus formicarius (Linnaeus, 1758), Thanasimus femoralis (Zetterstedt, 1828) (Cleridae) and Salpingus ruficollis (Linnaeus, 1761) (Salpingidae). Two more species – Glischrochilus quadripunctatus (Linnaeus, 1758) (Nitidulidae) and Pytho depressus (Linnaeus, 1767) (Pythidae) – were singly collected in the foci. T. formicarius and P. elongatum were the most abundant. The ratio of predator–prey significantly increased from the upper to the lower part of the stem with thick bark. It, however, decreased in this stem part from the fourth to the sixth class of the health condition of the host tree.

Evaluation of pheromone traps for bark beetles and their predators in pine forests in the Kharkiv region

“…Introduction. The pine stands of many regions have been affected by outbreaks of bark beetles with the dominance of Ips acuminatus (Gyllenhal, 1827) and Ips sexdentatus (Börner, 1776) (Colombari et al 2013, Liška et al 2021, Meshkova 2021, Lantschner & Corley 2023. As the foci of these insect species collapsed, the abundance of Tomicus piniperda (Linnaeus, 1758) and T. minor (Hartig, 1834) increased (Andreeva et al 2019).…”

“…Captures of predatory beetles in pheromone traps also varied throughout the season. The predator-to-prey ratio is typically very variable in different regions and foci (Warzee et al 2006, Wermelingeret al 2021, Meshkova et al 2022). According to our data, the average ratio in pheromone traps was 2.5 for the season.…”

Динаміка видового складу короїдів і їхніх хижаків із ряду Coleoptera у соснових насадженнях ДП «Жовтневе ЛГ» (Харківська обл.) у 2019–2022 рр.

“…Останнім часом у соснових лісах багатьох регіонів зареєстровано спалахи короїдів Ips acuminatus (Gyllenhal, 1827) та Ips sexdentatus (Börner, 1776) (Colombari et al 2013, Andreieva et al 2019, Meshkova & Bobrov 2020, Meshkova 2021, Wermelinger et al 2021. У згасанні цих спалахів в Україні значну роль відігравали ентомофаги, зокрема хижі комахи (Andreieva 2019, Zhukovsky et al 2020, Meshkova et al 2021a, 2022. У 2018 р. На ДСЛП «Харківлісозахист» розпочато розведення хижої комахи мурахожука Thanasimus formicarius (Linnaeus 1758) (Coleoptera: Cleridae).…”

“…У середньому випускали по 4-6 личинок хижака на одне дерево (Meshkova et al 2021b). Ефективність заходу оцінювали за зміною санітарного стану насаджень і популяційних показників короїдів, які визначали за даними обліку під корою модельних дерев на ділянках, де вносили хижака, і на контролі, де хижака не вносили (Meshkova et al 2022). Обліки короїдів та їхніх хижаків здійснювали також у пастках із метою виявлення видового складу комах, сезонної динаміки льоту й динаміки чисельності окремих видів хижаків упродовж спалаху короїдів.…”