Dispersal and larval hosts of the zigzag sawfly Aproceros leucopoda (Hymenoptera) in Slovakia, Central Europe

Background and purposeThe zigzag elm sawfly, Aproceros leucopoda (Hymenoptera), originating from Asia is being considered as one of the major pests of elm trees (Ulmus spp.) within Europe where it was first recorded in 2003. Recent investigations document the fast spread of this invasive species in many European countries. In Slovakia, A. leucopoda was first recorded in 2009 but its occurrence here has not been reported since 2009. Herein, we summarize the data from the two consecutive years about the current distribution of A. leucopoda and its hosts in Slovakia, Central Europe, focusing on infestation of elm trees by this successful invader in different altitudes.Material and methodsIn 2014 and 2015 the investigations of A. leucopoda were conducted at 101 different plots across the country. At each plot, characteristic symptoms of leaf damage, occurrence of larvae, cocoons or adults were recorded along with the geographical coordinates and the altitude, and the host trees of A. leucopoda were identified at the species level. The distribution map of A. leucopoda was drawn using the field data. The infestation of elm trees along the altitudinal gradient was analyzed with Kruskal-Wallis non-parametric analysis of variance followed by post-hoc Dunn\u27s test for multiple comparisons.Results and conclusionsThe zigzag elm sawfly A. leucopoda was observed at 31 plots (30.7%, n = 101). In elm trees examined, generally, a low level of infestation by this pest was observed. A. leucopoda was found at plots between 107 and 701 m a.s.l. The result show that the infestation level of elm trees was decreasing with increasing altitude. Although we had only a small sample of data, we assume that the altitude has a significant effect on distribution of this pest. The field elm (Ulmus minor Mill.) was the most frequently utilized host. Data collected document the establishment of this successful invader in Slovakia.</p

Spread and potential host range of the invasive oak lace bug [Corythucha arcuata (Say, 1832) - Heteroptera: Tingidae] in Eurasia

International audienceThe North American oak lace bug feeds on leaves of 'white oaks" in its native range. In Europe, it was first discovered in northern Italy in 2000. In recent years, it has subsequently spread rapidly and population outbreaks have been observed in several European countries. In the present study, we summarize the steps of its expansion. To predict its potential host range, we checked 48 oak species in 20 sentinel gardens in seven countries between 2013 and 2018. In total, 27 oak species were recorded as suitable hosts; 13 of them are globally new ones, 23 out of the 29 in section Quercus (similar to white oaks, an intrageneric taxonomic unit within genus Quercus), including Asian oaks, native to Japan, Korea and China, and four out of five in section Cerris (another intrageneric unit of the same genus), were accepted as hosts. None of the species in section Lobatae (red oaks) or in the Ilex group was accepted. Host records were also collected in forest stands of 10 countries. We found 11 oak species that were infested. Outbreak populations were most commonly found on Quercus robur, Quercus frainetto, Quercus petraea and Quercus cerris, comprising widespread and outstandingly important oaks species in Europe. Based on our findings, we conclude that suitable hosts for oak lace bug are present in most of Europe and Asia. This means that a lack of hosts will likely not restrict further range expansion