Outbreak of Orthotomicus erosus (Coleoptera, Curculionidae) on Aleppo Pine in the Mediterranean Region in Croatia

Milan Pernek; Nikola Lackovi?; Ivan Luki?; Nikola Zori?; Dinka Mato?evi?

摘要

Background and Purpose: Orthotomicus erosus, Mediterranean pine engraver, is widely distributed across the Mediterranean and southern Europe, Asia and North Africa. It is considered as secondary pest found on recently dead or felled trees, but can also attack weakened living trees. In high population levels this species can attack healthy trees and cause their dieback. Severe outbreaks occur after dry periods, or after fire in adjoining stands in warmer parts of the Mediterranean region, while this scenario has never happened in Croatia up to now. Bark beetles are important forest pests which have already been researched and discussed in relation to climate change, indicating that the predicted increase in temperature would lead to higher survival rates and faster development, thus directly influencing their population dynamics. Increase in temperature may stimulate changes in insects’ rate of development, voltinism, population density, size, genetic composition, extent of host plant exploitation, longitudinal and latitudinal distribution. Since climate conditions might have changed in the last few years as predicted in the Mediterranean region, the aim of our research is to document the first outbreak with high population levels of O. erosus in Croatia. Materials and Methods: The extent of dieback was evaluated by counting trees with dieback symptoms on diagonal transects plotted through each of 33 forest management sections of Marjan Forest Park (Split). Trunk sections from several trees with early stage symptoms were collected for further laboratory analysis, which consisted of incubation phase and subsequent morphological identification. During regular yearly surveys in forests of Croatia, the pest was observed on several sites and damages were recorded for both years 2017 and 2018. The records were entered into a map using QGIS version 3.2.1-Bonn. Spatial data was downloaded from DIVA-GIS server. Monitoring efforts were initiated in affected areas where 13 flight barrier pheromone traps (Theyson?) equipped with pheromone lure Erosowit? (Witasek, Austria) were set-up in late March in state-owned and privately owned forests across Dalmatia. Catches in the traps were collected and O. erosus adults were counted on a weekly basis in order to identify the abundance of the pest in monitored sites, as well as to obtain the first information about population dynamics and to assess voltinism. Results: On-site survey and the evaluation of dieback extent included sampling of 5% of all trees in Marjan Forest Park ,and the results showed that 23% of all trees in the forest park were affected by dieback symptoms. Visual examination of trunks, branches and bark showed symptoms of bark beetle infestation, while preliminary on-site examination of the observed adults pointed out to O. erosus. After two weeks in controlled conditions, bark beetle adults started to emerge from trunk sections which were placed in several mesh cages for incubation. Morphological identification by using stereomicroscope and the key for European bark beetles resulted in identification of O. erosus species. Over the course of the year 2017 one more site was reported to be infested with O. erosus, and eight additional sites were reported over the course of year 2018. In total, 446 ha were reported as infested, varying in intensity, in several different management units of state-owned and privately owned forests. The total number of trapped beetles in pheromone traps varied largely among sites. Our data indicate that several generations (at least 5 generations per year) were present in the year 2018. Conclusions: Sudden surge in observed damages, as well as the number of beetles trapped during monitoring, in years 2017 and 2018 throughout Aleppo pine forests in Dalmatia are the first record of O. erosus outbreak in Croatia. O. erosus is native to Croatia and so far it has been considered only as a minor pest whose outbreaks have never been recorded. Drought intensity and frequency and aridification trends in the research area (Dalmatia, Croatia) cause cumulative stress to trees and have increased O. erosus occurrence. O. erosus is expected to exhibit increased voltinism, better overwintering performance and earlier spring flights. Our first results confirm this epidemic stage of O. erosus with high abundances in Dalmatia in 2018 and at least 5 generations per year, which alter the population level of this pest. Finally, with high dispersal abilities of O. erosus through active flight and easy transportation with infested material (logs and branches with bark), O. erosus has the potential to become an important forest pest in Croatia. Thus, extensive studies on its biology, ecology, natural enemies and interaction with ophiostomatoid fungal species are needed in order to predict further spread and suggest viable and effective management measures.

机译：背景和目的：地中海松雕刻机Orthotomicus erosus广泛分布于地中海和南欧，亚洲和北非。它被认为是在最近死亡或砍伐的树木上发现的次生害虫，但也可能袭击弱化的活树。在高种群水平下，该物种会攻击健康的树木并导致其死亡。在干旱时期之后，或在地中海地区较温暖的地区，相邻林分发生火灾后，爆发严重疫情，而这种情况迄今为止在克罗地亚从未发生过。树皮甲虫是重要的森林害虫，已经针对气候变化进行了研究和讨论，表明预测的温度升高将导致更高的成活率和更快的发育，从而直接影响其种群动态。温度的升高可能会刺激昆虫的发育速度，Voltinism，种群密度，大小，遗传组成，寄主植物开发的程度，纵向和横向分布的变化。正如地中海地区所预测的那样，由于最近几年的气候条件可能已经发生变化，因此我们的研究目的是记录克罗地亚首次发生的高人群O. erosus暴发。材料和方法：通过对在Marjan森林公园（Split）的33个森林经营区中的每一个绘制的对角样带上有死皮症状的树木进行计数，评估了死皮的程度。收集具有早期症状的几棵树的树干部分，以进行进一步的实验室分析，包括潜伏期和随后的形态鉴定。在克罗地亚森林的年度例行调查中，在多个站点上均观察到了有害生物，并记录了2017年和2018年的破坏情况。使用QGIS版本3.2.1-Bonn将记录输入到地图中。空间数据是从DIVA-GIS服务器下载的。在受影响地区启动了监测工作，在这些地区，有13个装有信息素诱饵Erosowit？的飞行障碍信息素陷阱（他们是爱森？）。（奥地利Witasek）于3月下旬在整个达尔马提亚的国有和私有森林中成立。收集诱捕器中的渔获物，并每周对O. erosus成年动物进行计数，以便确定所监测地点的有害生物数量，并获得有关种群动态的第一信息并评估伏牛病。结果：现场调查和对枯萎程度的评估包括对马里安森林公园所有树木的5％的采样，结果表明，森林公园中所有树木的23％受枯萎症状的影响。肉眼检查树干，树枝和树皮显示出树皮甲虫侵扰的症状，而对所观察到的成虫进行的初步现场检查则指出了O. erosus。在受控条件下两周后，树皮甲虫成虫开始从树干部分出来，这些树干被放置在几个网箱中进行孵化。使用体视显微镜的形态学鉴定和欧洲树皮甲虫的钥匙导致鉴定了O. erosus物种。据报告，在2017年期间，又有一个地方感染了O. erosus，在2018年期间又报告了另外8个地方。据报道，总共有446公顷被侵染，强度有所不同。国有和私有森林的管理单位。信息素诱捕器中被捕获的甲虫总数在不同地点之间差异很大。我们的数据表明，2018年有数代（每年至少5代）。结论：2017年和2018年，阿勒颇松林中的观察到的损害以及在监测过程中捕获的甲虫数量突然增加。达尔马提亚是克罗地亚O. erosus爆发的第一记录。 O. erosus原产于克罗地亚，到目前为止，它仅被视为一种从未记录过爆发的轻微害虫。研究区域（克罗地亚达尔马提亚）的干旱强度和频率以及干旱化趋势导致树木累积压力，并增加了O. erosus的发生。预计O. erosus会显示出更多的伏牛病，更好的越冬性能和更早的春季飞行。我们的第一个结果证实了2018年在达尔马提亚存在高丰度的O.erosus流行阶段，每年至少发生5代，这改变了该害虫的种群水平。最后，凭借活跃的飞行和广泛利用被侵染的物质（带有树皮的原木和树枝）进行运输的O. erosus具有高分散能力，O。erosus有可能成为克罗地亚重要的森林害虫。因此，需要对其生物学，生态学，天敌以及与类蛇类真菌种类的相互作用进行广泛研究，以便预测其进一步传播并提出可行和有效的管理措施。

Outbreak of Orthotomicus erosus (Coleoptera, Curculionidae) on Aleppo Pine in the Mediterranean Region in Croatia

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