Presence of Contarinia pseudotsugae suspected in Belgium
Since the beginning of 2015, the presence of unusual symptoms has been observed on Pseudotsuga menziesii (Douglas fir) trees growing in Walloon forests, Belgium. Samples were collected and sent to the laboratory of CRA-W (Centre Wallon de Recherches agronomiques). Symptoms were characterized by brownish to reddish or purplish discolorations on the current years’ needles. Affected needles were swollen or bent. Results showed that in addition to fungal pathogens (Phaeocryptopus gaeumanii and Sirococcus conigerus), larvae of an insect, tentatively identified as Contarinia pseudotsugae (Diptera: Cecidomyiidae – Douglas fir needle midge), were also present. As only larval stages could be found in Belgium, a final identification was not possible. Three North American species: C. pseudotsugae, C. cuniculator and C. constricta are known to cause this type of symptoms on P. menziesii. Deformations observed on needles correspond to the presence of galls induced by larvae, and those observed in Belgium resembled those that are caused by C. pseudotsugae. In addition, it is noted that in North America, among the three Contarinia species, C. pseudotsugae is the most abundant one. Recent observations made in the Walloon region suggest that the insect is established and widespread, as signs of its presence were noted in all visited sites (more than 30 in Ardennes, Famenne and Lorraine). On these sites, low infestation levels were found (10%). However, infestation levels reaching 50% have been observed in some young plantations. Interestingly, similar findings have been made in the Netherlands (see EPPO RS 2016/008). If the identity of the pest is confirmed, these new records in Belgium and the Netherlands would be the first ones of this North American needle midge in the EPPO region.
OWSF. La santé des forêts en Wallonie. Contarinia pseudotsugae: un nouvel insecte détecté sur Douglas. http://owsf.environnement.wallonie.be/fr/26-11-2015-contarinia-pseudotsugae-un-nouvel-insecte-detecte-sur-douglas.html?IDD=4971&IDC=5798