Pathogenicity of Lophodermium species on Scots pine
Literature on three Lophodermium species (i.e. L. pinastri (Schrad.) Chev., L. conigenum Hilitzer and L. seditiosum Minter, Staley and Millar) is reviewed. Possible sources of inoculum for the infection by L. seditiosum are investigated. Needles which fall in spring and early summer are found to be the most important source of inoculum. Cones in the litter are found to have more L. seditiosum ascocarps than the other Lophodermium species but the number of ascocarps is far less than that found on needles. Ascospores of the three species have an optimal germination temperature of 25°C. L. seditiosum ascospores show the highest percentage germination and L. pinastri ascospores the lowest. With all the three species, penetration into the host tissue is by direct cuticular penetration by germ-tubes from melanized appressoria. Out of the three species, only L. seditiosum is found to be pathogenic. Infection and colonization of tissue by L. seditiosum is favoured in needles under high rather than low water potentials.