Citation: Stanc˘ a-Moise, C.; Moise, G.; Rotaru, M.; Vonica, G.; Sanislau, D. Study on the Ecology, Biology and Ethology of the Invasive Species Corythucha arcuata Say, 1832 (Heteroptera: Tingidae), a Danger to Quercus spp. in the Climatic Conditions of the City of Sibiu, Romania. Forests 2023, 14, 1278. https://doi.org/10.3390/f14061278 Academic Editors: Timothy A. Martin and Cate Macinnis-Ng Received: 18 April 2023 Revised: 12 June 2023 Accepted: 16 June 2023 Published: 20 June 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Study on the Ecology, Biology and Ethology of the Invasive Species Corythucha arcuata Say, 1832 (Heteroptera: Tingidae), a Danger to Quercus spp. in the Climatic Conditions of the City of Sibiu, Romania Cristina Stancă-Moise 1, * , George Moise 1 , Mihaela Rotaru 2 , Ghizela Vonica 3 and Dorina Sanislau 1 1 Department of Agricultural Sciences and Food Engineering, Faculty of Agricultural Sciences, Food Industry and Environmental Protection, “Lucian Blaga” University of Sibiu, 5–7 Ion Ratiu Street, 550003 Sibiu, Romania 2 Department of Industrial Engineering and Management, Faculty of Engineering, “Lucian Blaga” University of Sibiu, 4 Emil Cioran Street, 550025 Sibiu, Romania 3 National Brukenthal Museum, Natural History Museum, No. 1 Cetatii Street, 550160 Sibiu, Romania * Correspondence: cristinamoise1@yahoo.com or cristina.moise@ulbsibiu.ro Abstract: This scientific paper examines the impact of climate change on the spread and survival of the invasive species Corythucha arcuata Say, 1832 (oak lace bug, or OLB) in Romania. The OLB is native to the Eastern USA and Canada, and in its native habitat, it coexists with minimal impact to the preferred host plant species Quercus. However, in Europe, the OLB in high density causes early defoliation, slowing tree growth. As Quercus spp. is a keystone species, the impact of the OLB on European forests is significant. This paper aims to address several gaps in knowledge about the OLB by presenting findings from a study conducted by the Lucian Blaga University of Sibiu (ULBS) in Romania. The study identified the species’ chronology of spread, ecology, ethology and biology of the species, in addition to foliage classification to determine the extent of attack. The study found a direct link between the temperature and the speed of the generational lifecycle. The findings support the thesis that climate change is enabling the healthy, rapid density growth of OLB, which is a danger to the Quercus spp. Further research is needed in the area of the thermal tolerance of the OLB, and the research conducted by the ULBS represents the first documented research into the thermal constant of the insect. The paper concludes that further research must be in the direction to understand how and where these insects survive during winter to find future management measures and identify chemical or biological methods as solutions to eradicate and stop the expansion of the invasion of the OLB, and the potential consequences for the Quercus sp. Keywords: oak lace bug; invasive alien species; Corythucha arcuata (Say, 1832); Sibiu County; Romania 1. Introduction Corythucha (Stål) belongs to the Hemiptera Order, Tingidae Family. The genus was first described in 1873 by Say. In total, 70 species have been described belonging to this genus [1]. California is home to more than a dozen species of lace bugs. According to Gibson (1918), the host plants preferred by species of the Corythuca genus belong to the genera Alnus Mill., Malus Mill., Betula L., Stpthylea L., Aesculus L., Juglans L., Cephalanthus L., Prunus L., Pyrus L., Ulmus L., Ribes L., Quercus L., Rosa L., Populus L., Celtis L., Crataegus L., Corylus L., Aesculus L., Tilia L., Amelanchier Medik., Carya Nutt., Rhus L., Carduus L., Cirsium Mill., Lathyrus L., Salix L. [2]. The Corythucha arcuata Say, 1832, (the oak lace bug (OLB)) species is native to North America, where it is classified as very common. Each feed on a single or a small number of closely related plant species. Alder, ash, avocado, coyote brush, birch, ceanothus, photinia, poplar, sycamore, toyon and willow are among potential hosts [3]. Forests 2023, 14, 1278. https://doi.org/10.3390/f14061278 https://www.mdpi.com/journal/forests