Life history and geographical distribution of the walnut twig beetle, Pityophthorus juglandis (Coleoptera: Scolytinae), in southern Europe. (1st February 2016)

• Record Type: Journal Article
• Authors: Faccoli, M.; Simonato, M.; Rassati, D.
• Is Part Of: Journal of applied entomology. Volume 140:Number 9(2016)
• Page Start: 697
• Page End: 705
• Publication Date: 2016-02-01
• Subjects: alien species -- bark beetles -- biological invasions -- forest pest -- monitoring -- thousand cankers disease; Entomology -- Periodicals; Insect pests -- Periodicals; 595.7
• DOI: 10.1111/jen.12299
• Languages: English
• ISSNs: 0931-2048

Abstract

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. The collected adults were found to be vector of the fungus Geosmithia morbida Kolařik, Freeland, Utley & Tisserat, an aggressive pathogen causing thousand cankers disease in walnut ( Juglans spp.). To determine the geographical distribution of the WTB and the main aspects of biology, phenology and voltinism, an intensive survey of the main walnut plantations near the site of the first finding was conducted in 2014. The beetles began to fly with a mean air temperature of about 18°C (mid‐May) and continued until late October. Two partially overlapping generations occurred, with the second taking place in late September. The WTB was found in 14 of the 27 monitored walnut plantations. The infested sites were spread over four different non‐contiguous administrative provinces belonging to two regions (Veneto and Lombardy) of northern 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 the WTB in northern Italy may be prudently estimated at about 4200 km 2 . Molecular analysis of the collected individuals showed no genetic differences among the six sampled P. juglandis populations, suggesting that a few individuals might have arrived in Italy through a single introduction event and then spread over the territory. Given the quick mortality of infested walnuts and the wide distribution area, eradication strategies appear unrealistic. Possible strategies of biological control or local chemical treatments must be investigated.