The reason of the epiphytoty in the provenance trials of the Siberian (Pinus sibirica Du Tour) and Korean (Pinus koraiensis Siebold et Zucc.) stone pines in the foothills of the Western Sayan (south of Krasnoyarsk territory) was established. The cause of stone pine needles drying was disease – grey pine-leaf cast (grey Schutte). The causative agent was pathogenic fungus Lophodermella sulcigena. The Siberian stone pine trees of Tashtagolskii climate type were drying (fatally) to the greatest extent (21 %). The populations of the Korean stone pine showed higher resistance to fungal infections comparing to the Siberian stone pine climate type.