Thousand cankers disease of walnut in Europe: impact, diagnosis and control

Thousand cankers disease (TCD) causes branch dieback and mortality of walnut, especially black walnut (Juglans nigra) in natural forests, plantations and ornamental greenery. The disease is the result of the aggressive feeding by the bark beetle Pityophthorus juglandis on walnut trees and the subsequent development of a multitude of coalescing cankers by the ascomycete fungus Geosmithia morbida around beetle galleries. These assays, based on duplex real-time PCR, SYBR Green qPCR and LAMP, could validly support phytosanitary services in surveillance campaigns. In fact, being both members of the TCD pest complex difficult to identify with traditional methods, the use of molecular tools could assist in the phytosanitary inspection of import/export plant material as well as of plantations, nurseries and urban greenery.