In September 2013, the Walnut Twig Beetle (WTB) Pityophthorus juglandis Blackman, a species native to Mexico and South-Western USA, was recorded for the first time in Europe in Northern Italy (Province of Vicenza). The collected adults were found to be vector of the fungus Geosmithia morbida Kolařik (Ascomycota: Hypocreales), an extremely aggressive pathogen inducing the Thousand Cankers Disease (TCD) on walnut species (Juglans spp.). In order to determine the geographical distribution of the species and the main aspects of its biology, phenology and voltinism, an intensive survey of the main walnut plantations occurring near to the first finding site was carried out in 2014. The beetles began to fly with a mean air temperature of about 18° C (middle May) and continued until late October. Two partially overlapping generations occurred, with the second one tooking place in late September. WTB was found in the half (14) of the 28 monitored walnut plantations. The infested sites were spread over 4 different non-contiguous administrative provinces (Vicenza, Padova, Treviso and Mantova) belonging to two regions (Veneto and Lombardy) of North Italy. The most distant infested plantations were about 130 km apart along a west-east gradient, and about 70 km along a north-south gradient. In this respect, the distribution area of WTB in North Italy may be estimated prudentially in about 4,200 km2 . All the monitored sites occurring within a radius of about 30 km around the first infestation were found positive to WTB and TCD. Molecular analysis of the trapped specimens showed no genetic variability in P. juglandis populations, suggesting that few individuals of WTB might be arrived in Italy through a single introduction event. Given the quick mortality of infested walnuts and the wide distribution area, eradication strategies appear unrealistic. Further strategies of biological control or local chemical treatments must be investigated.
Bioecologia e distribuzione di Pityophthorus juglandis (Coleoptera: Curculionidae, Scolytinae) in Italia
Faccoli M.;Montecchio L.
2015
Abstract
In September 2013, the Walnut Twig Beetle (WTB) Pityophthorus juglandis Blackman, a species native to Mexico and South-Western USA, was recorded for the first time in Europe in Northern Italy (Province of Vicenza). The collected adults were found to be vector of the fungus Geosmithia morbida Kolařik (Ascomycota: Hypocreales), an extremely aggressive pathogen inducing the Thousand Cankers Disease (TCD) on walnut species (Juglans spp.). In order to determine the geographical distribution of the species and the main aspects of its biology, phenology and voltinism, an intensive survey of the main walnut plantations occurring near to the first finding site was carried out in 2014. The beetles began to fly with a mean air temperature of about 18° C (middle May) and continued until late October. Two partially overlapping generations occurred, with the second one tooking place in late September. WTB was found in the half (14) of the 28 monitored walnut plantations. The infested sites were spread over 4 different non-contiguous administrative provinces (Vicenza, Padova, Treviso and Mantova) belonging to two regions (Veneto and Lombardy) of North Italy. The most distant infested plantations were about 130 km apart along a west-east gradient, and about 70 km along a north-south gradient. In this respect, the distribution area of WTB in North Italy may be estimated prudentially in about 4,200 km2 . All the monitored sites occurring within a radius of about 30 km around the first infestation were found positive to WTB and TCD. Molecular analysis of the trapped specimens showed no genetic variability in P. juglandis populations, suggesting that few individuals of WTB might be arrived in Italy through a single introduction event. Given the quick mortality of infested walnuts and the wide distribution area, eradication strategies appear unrealistic. Further strategies of biological control or local chemical treatments must be investigated.Pubblicazioni consigliate
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