Fig 1.
A male of Xylotrechus chinensis.
(A) Posing alert on a mulberry bolt. (B) Close-up of male head. (Photos V. Sarto i Monteys).
Fig 2.
Xylotrechus chinensis in Europe up to July 2020.
Source map reprinted from https://commons.wikimedia.org/wiki/File:Europe_map.png under a CC BY license, with permission from Wiki-vr, Public domain, via Wikimedia Commons. 30 November 2013.
Fig 3.
Catalonian districts invaded by Xylotrechus chinensis up to July 2020.
The four townships invaded up to July 2018 are in orange; the eight new townships invaded up to July 2020 are in red. The black asterisk signals the city of Barcelona. Source map of Catalonia obtained from BDLJE CC-BY 4.0 Spanish ‘Instituto Geográfico Nacional’ http://www.ign.es/. The districts and towns were reproduced from the Cartographic and Geological Institute of Catalonia, https://www.icgc.cat/, under a CC BY 4.0 license. The data were assembled using ArcMap 10.3.1 (May 13, 2015) https://desktop.arcgis.com/es/arcmap/10.3/main/map/what-is-arcmap-.htm.
Fig 4.
X. chinensis infestation indicators on mulberry trees.
(A) Adult beetle emergence holes (most coloured orange) on the trunk of a tree. (Photo G. Torras). (B to D) Bark injury caused by beetle larvae: (B) as seen before removing the dead and dry periderm to discover the feeding gallery underneath, and one beetle larva (C) and (D). (Photos J. Serra). (E-F) Gallery slits caused by beetle larvae: (E) on the trunk, (F) on the crown base. Coloured spots signal emergence holes. (Photos G. Torras (E); V. Sarto i Monteys (F)).
Fig 5.
Satellite map of the town of Barberà del Vallès showing in green the location of its 506 public mulberry trees in 2016.
(Map source: Cartographic and Geological Institute of Catalonia, https://www.icgc.cat/, under a CC BY 4.0 license, accessed 27 April 2020).
Fig 6.
A mulberry tree showing the 50 cm-height bands established for positioning indicators of infestation.
In this tree, the top band on the trunk measures only 25 cm before reaching the crown base from the fourth 50 cm-trunk band. Coloured spots signal emergence holes. (Photo G. Torras).
Fig 7.
Graph sorting trees according their sum number of infestation indicators (EH+BI+GS) in June and in December 2018.
Table 1.
Trees sorted according their sum number of infestation indicators (EH+BI+GS) in June and in December 2018.
Fig 8.
Summary counts for the three established infestation indicators, comparing the June and December 2018 surveys.
For June 2018 figures include the 438 trees initially checked, as well as, again, for only the same 408 trees also present in December 2018, this for comparative reasons (see text).
Table 2.
Tree infestation by X. chinensis based on trunk height (from ground to crown base).
Fig 9.
Tree infestation by X. chinensis based on trunk perimeter.
In both graphs the 30 trees missing in December were incorporated into the counts as if they were present with the same values they had in June. The top graph shows the trees infested within each perimeter range. The bottom graph shows the sum of damages (EH+BI+GS) for all trees within their range (total damages being 2,103), and the expected damages if their distribution was neutral, i.e. with no preferences for laying on any trunk perimeter range. Percentage values in red or green tell the difference between the expected and the observed.
Fig 10.
Quadratic functions corresponding to the coefficients identified in the models for perimeter and squared perimeter—with other variables assumed to be zero.
BI+GS stands for bark injuries and gallery slits combined.
Fig 11.
Distribution of emergence holes (EH) on orientation and height.
Fig 12.
Distribution of bark injuries (BI) on orientation and height.
Fig 13.
Distribution of gallery slits (GS) on orientation and height.
Fig 14.
Distribution of emergence holes, bark injuries and gallery slits combined (EH+BI+GS) on orientation and height.
Table 3.
Wilcoxon test for the distribution of infestation damages on trunk and crown base (per 1000 cm2).
Table 4.
Regression results with NBRM for EH, BI and GS considered separately.
Table 5.
Regression results with NBRM for BI and GS combined.