I had a look at these trees today. My first thoughts were massaria however I have only seen massaria infecting and killing individual limbs. These tres look like they been nuked!!! To my eye it appears that one side of the avenue has been affected far more than the other side although there is apparent crown die back on that side too.
Symptoms-Description
C. fimbriata is primarily a xylem pathogen. On trees (Theobroma, Mangifera, Prunus, etc.), infection typically occurs through fresh wounds (Giraldo, 1957; Viégas, 1960; Moller et al., 1969), although root infections are also common (Ribeiro et al., 1986; Rossetto and Ribeiro, 1990; Laia et al., 2000). Mycelium and spores enter wounds and move through the xylem in water-conducting cells and into ray parenchyma cells. The fungus causes dark reddish-brown to purple to deep-brown or black staining in the xylem. This staining may extend several metres from the roots, up the trunk of the tree, and into branches. When affected branches or trunks are cut in cross-section, the staining along the rays gives a distinctive wedge-shaped or starburst-like pattern (Sinclair et al., 1987). On the surface of the trunk or branches, cankers may develop over areas of xylem discoloration, and the cankers may exude gum. Branch and trunk cankers are particularly common on Populus, Prunus, Platanus (Sinclair et al., 1987) and Eucalyptus (Laia et al., 2000), though wilting may also occur in the absence of canker development. Wilted leaves typically become dry and curled rather suddenly but remain attached to the tree for several weeks. On Platanus, individual leaves of affected branches often show interveinal chlorosis and necrosis, perhaps associated with fungal-produced phytotoxins (Ake et al., 1992; Alami et al., 1998; Pazzagli et al., 1999
Means of movement and dispersal
Natural dispersal
The fungus spreads readily between adjacent Platanus trees via root grafts (Accordi, 1986). It may also infect Platanus trees through wounds in the roots (Vigouroux and Stojadinovic, 1990). Mangifera trees may be infected through the roots from soilborne inoculum (Rossetto and Ribeiro, 1990), and root crops such as Ipomoea are commonly infected through wounds made by insects and rodents (Clark and Moyer, 1988). Ascopores are probably spread naturally by insects and are not likely airborne. Airborne disperal of conidia is also not likely, except in insect frass. Rainsplash dispersal of conidia has not been documented.