First report of Geosmithia morbida and its insect vector (Pityophthorus juglandis)
In the USA, the association of a recently described fungal species, Geosmithia morbida, and its vector, Pityophthorus juglandis (Coleoptera: Scolytidae - walnut twig beetle), is causing a severe and emerging disease of black walnut (Juglans nigra) and other Juglans species or hybrids. This disease is called thousand cankers disease and, until recently it had not been reported from any other parts of the world. At the end of November 2013, the NPPO of Italy informed the EPPO Secretariat of the first records of G. morbida and P. juglandis on its territory. Both pests were found in the municipality of Bressanvido (province of Vicenza, Veneto region) on a small number of J. nigra trees, and their identity was confirmed by laboratory analysis (morphology, molecular tests) on 2013-09-27. The infected trees (approximately 15 years old) were part of a plantation grown for wood production. Leaf yellowing and wilting, twig and branch dieback were observed, as well as numerous small bark cankers developing around galleries made by P. juglandis. This outbreak was discovered because the owner of the plantation had contacted Prof. Montecchio at the University of Padova where the identification was performed. In a paper to be published, Montecchio & Faccoli (2014) explain that the disease was also detected in Bressanvido on 80-year old J. nigra trees in a private garden. The origin of this outbreak is unknown. The most likely pathway is thought to be the introduction of the insect vector on wood (with bark) from the USA. The discovery of thousand cankers disease is considered by the NPPO as a serious threat to J. nigra, and possibly to J. regia which is susceptible to the disease, although apparently to a much lesser degree, in the USA. It is noted that during the last 90 years, numerous areas along the Po valley have been reforested with mixed tree species for wood production, in which J. nigra is often present in varying proportions. Systematic surveys will be conducted near the outbreak site to determine the extent of the infection. Random checks will also be carried out in J. nigra plantations across the Veneto region. Studies will be conducted on the potential pathways of entry of this new disease, in particular in sawmills where walnut wood is imported from the USA. Phytosanitary measures to eradicate the disease are being considered.
The pest status of both Geosmithia morbida and Pityophthorus juglandis in Italy is officially declared as1: Outbreak found in one locality in Veneto region, monitoring surveys and eradication measures are being adopted.
1 Translated from the Italian: ‘Focolaio rinvenuto in una località della Regione Veneto, attività di monitoraggio e misure di eradicazione in corso di adozione’.
Montecchio L, Faccoli M (2014) First record of thousand cankers disease Geosmithia morbida and walnut twig beetle Pityophthorus juglandis on Juglans nigra in Europe. Plant Disease 98(in press).
NPPO of Italy (2013-11).