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a plant disease caused by various fungi, both saprophytes and hemiparasites. It affects fruit and berry crops (including citrus, grape, mulberry), cereal grains, hops, house-plants, hothouse plants, and certain forest trees. It occurs mainly in subtropical and tropical climates. Black and dark brown spots and films (mycelia and spore sacs of fungi) appear on affected plants, decreasing photosynthetic activity and obstructing access of air to the tissues. Black rust is especially damaging to spikes and caryopses of cereal grains, lowering the yield and quality of wheat, rye, and millet grains. Control measures consist mainly in destroying aphids and scale insects, upon whose discharges the causative agents feed.