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leaf cast[′lēf ‚kast]
a disease of coniferous needles caused by pathogenic fungi. There are three types of leaf cast. The most common is caused by ascomycetes of the genus. Lophodermium. A second type is caused by the ascomycete Phacidium infestons, and a third by the imperfect fungi of the genus Meria.
Symptoms of leaf cast are yellowing and then browning and falling of the needles. In leaf cast caused by Phacidium infestans, a white gossamer-like mycelium appears in the spring; the needles turn brown, and by autumn they are ash-gray. Leaf cast is especially dangerous in tree nurseries. Control measures include removal and burning of dead plants and fallen needles, pinching off diseased needles, arid spraying seedlings (before the formation of the snowy covering) with a suspension of zineb or other fungicides.