21/03/2022 1 min

Understanding the increase in damage caused by a fungus in the Landes forest

For the past three years, Cronartium pini, a fungus responsible for pine blister rust, has been causing increasing damage to maritime pines in the Landes forest. Work by the Plant Health Laboratory's Mycology Unit has shown that the nearby establishment of peony fields was not responsible, although it had increased its transmission and aggravated the extent of the damage it had caused.

Over the last three years, Cronartium pini has affected nearly 800 hectares of forest in the south of the Landes départment. When maritime pines are contaminated by the fungus, it prevents their sap from circulating, killing the trees, especially in young plantations. The Mycology Unit of ANSES's Plant Health Laboratory conducted a research project to genetically characterise the strains of the fungus. This project, financed by the Phyto Forêt Fund, was developed jointly by ANSES and the Nouvelle-Aquitaine Region's Forest Health Department. The characterisation was based on the study of short DNA sequences called microsatellites. It was carried out in collaboration with ANSES's Nancy Laboratory for Rabies and Wildlife, which contributed its expertise and equipment.

The population of fungi affecting the pines was compared with that found on the peonies. This is because peonies, along with other herbaceous species, act as hosts for the fungus, allowing it to complete its life cycle. Peony fields were recently planted near the patches of pine trees where the disease had progressed, and the study showed that these constitute a reservoir of contamination. Identifying the source of the contamination will enable suitable control measures to be established, thereby slowing down or even stopping the spread of the disease, which has a major economic impact on foresters.