Hosts and distribution of Collybia fusipes in France and factors related to the disease's severity

Using data collected by two different observation networks, it was possible to clarify the distribution of Collybia fusipes in France. It is frequently found in the western and northern parts of France, mainly on Quercus rubra and Quercus robur , and to a somewhat lesser extent on Quercus petraea . When the relative areas covered by these species are compared, it is evident that Q. rubra is much the most susceptible of the three species. The fungus has been less frequently reported in the south‐eastern quarter of France, where Quercus ilex and Quercus pubescens are the dominant species. Complementary observations carried out at the National Arboretum of Les Barres indicate that a large number of oak species are susceptible to infection by this fungus, particularly those in the subgenus Erythrobalanus . These observations are discussed with reference to reports of this fungus throughout Europe. In a Q. rubra stand, fruit‐body clumps were monitored and root damage was assessed on 73 final‐crop trees and 40 codominant trees. The results suggest that C. fusipes does not preferentially infect weakened trees. Both the severity of root damage and the number of fruit‐body clumps increased with increasing depth to signs of waterlogging.