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

Producción CientíficaThe 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,European Cooperation in Science and Technology (COST Action FP1406 PINESTRENGTH)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-69370-R)Centro de Estudios do Ambiente e do Mar (CESAM) (project UID/AMB/50017/2019)Portuguese Foundation for Science and Technology (projects PTDC/AGR-FOR/2768/2014 , POCI-01-0145-FEDER-016785 , SFRH/BPD/122928/2016)Russian Foundation for Basic Research (grant 17-04-01486)Saint Petersburg State Polytechnical University (project 2019-0420

Pine Pitch Canker and Insects: Regional Risks, Environmental Regulation, and Practical Management Options

Producción CientíficaPine pitch canker (PPC), caused by the pathogenic fungus Fusarium circinatum (Nirenberg and O’ Donnell), is a serious threat to pine forests globally. The recent introduction of the pathogen to Southern Europe and its spread in Mediterranean region is alarming considering the immense ecological and economic importance of pines in the region. Pines in forests and nurseries can be infected, resulting in severe growth losses and mortality. The pathogen is known to spread in plants for planting and in seeds, and results from recent studies have indicated that F. circinatum may also spread through phoretic associations with certain insects. With this review, we aim to expand the current understanding of the risk of insect-mediated spread of PPC in different parts of Europe. Through the joint action of a multinational researcher team, we collate the existing information about the insect species spectrum in different biogeographic conditions and scrutinize the potential of these insects to transmit F. circinatum spores in forests and nurseries. We also discuss the impact of environmental factors and forest management in this context. We present evidence for the existence of a high diversity of insects with potential to weaken pines and disseminate PPC in Europe, including several common beetle species. In many parts of Europe, temperatures are projected to rise, which may promote the activity of several insect species, supporting multivoltinism and thus, further amplifying the risk of insect-mediated dissemination of PPC. Integrated pest management (IPM) solutions that comply with forest management practices need to be developed to reduce this risk. We recommend careful monitoring of insect populations as the basis for successful IPM. Improved understanding of environmental control of the interaction between insects, the pathogen, and host trees is needed in order to support development of bio-rational strategies to safeguard European pine trees and forests against F. circinatum in future.European Cooperation in Science and Technology (COST Action FP1406 PINESTRENGTH)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-69370-R)Portuguese Foundation for Science and Technology (contract IF/00471/2013/CP1203/CT0001)Russian Foundation for Basic Research (grant 17-04-01486)Saint Petersburg State Polytechnical University (project 2019-0420