Pine Pitch Canker and Insects: Relationships and Implications for Disease Spread in Europe

The fungal pathogen Fusarium circinatum (Nirenberg and O’ Donnell) is the causal agent of pine pitch canker (PPC) disease, which seriously affects conifer species in forests and nurseries worldwide. In Europe, PPC is only established in the Iberian Peninsula; however, it is presumed that its range could expand through the continent in the near future. Infection caused by this fungus requires open wounds on the tree, including physical damage caused by insects. Therefore, a relationship probably occurs between PPC and a wide variety of insects. The aim of this review is to outline the taxonomic and ecological diversity of insect species with high potential association with F. circinatum in Europe and elsewhere. The insects were classified as vectors, carriers and wounding agents according to the association level with the PPC disease. In addition, we discuss the insect-mediated spreading of PPC disease in relation to the different phases of forest stand development, from seeds and seedlings in nurseries to mature stands. Lastly, to improve our predictive capacities and to design appropriate intervention measures and strategies for controlling disease dissemination by insects, variables such as geographic location, time of the year and host species should be considered. Our review provides a framework of the multiple factors that regulate the insect–host interactions and determine the success of the infection.

This study was made possible through the project “Etiology, Epidemiology and Control of Fusarium circinatum” sponsored by the Ministry of Rural, Marine, and Natural Environment, and with the support of the Government of Cantabria. This article is based upon work from COST Action FP1406 PINESTRENGTH (Pine pitch canker strategies for management of Gibberella circinata in greenhouses and forests) supported by COST (European Cooperation in Science and Technology) and project AGL2015-69370-R funded by MINECO and FEDER. This work is a contribution of URGENTpine (PTDC/AGR-FOR/2768/2014) funded by Fundação para a Ciência e a Tecnologia, I.P., through national funds, and the co-funding by the FEDER (POCI-01-0145-FEDER-016785), within the PT2020 Partnership Agreement and Compete 2020. Thanks for financial support are due to CESAM (UID/AMB/50017/2019), to FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. FCT also supported J.M.-G. (SFRH/BPD/122928/2016). P.N. would like to thank funding by the Fundação para a Ciência e Tecnologia—FCT (contract IF/00471/2013/CP1203/CT0001), Portugal. D.L.M.’s contribution was also supported by The Russian Foundation for Basic Research (Grant No. 17-04-01486). A.V.S.’s contribution was also supported by the Center for collective use of scientific equipment "Renewable resources, energy sources, new materials and biotechnology (SPbFTU)" (Project 2019-0420).