Peach leaf-curl (_Exoascus deformans_ (Berk.) Fuckel) is the best-known and probably the most prevalent fungus disease of the peach in New York. The disease appears in early spring as the leaves unfold and continues until warm, dry, summer weather prevails. The name describes the disease so that all may know it--the leaves curl, then become puckered, distorted and much thickened, turn from normal green to yellow, tinged with red, and finally fall. In severe cases the trees may be defoliated, though a second covering of leaves almost always comes out. Leaf-curl is most prevalent and most virulent in cool, moist weather. The disease is easily controlled by spraying with lime-sulphur, bordeaux mixture or any other good fungicide applied while the trees are dormant. In common with other species of Prunus the foliage of peaches is attacked by several fungi which produce diseased spots on the leaves, the dead areas usually dropping out leaving holes as if punctured by shot, giving the names "shot-hole fungus," "leaf-spot" and "leaf-blight." Two fungi are in the main responsible for these leaf-troubles, _Cylindrosporium padi_ Karsten and _Cercospora circumscissa_ Saccardo. The ravages of these fungi are prevented by the use of the self-boiled lime-sulphur mixture. With these, as with other fungi, cultivation has a salutary effect as it destroys diseased leaves which harbor the fungi during their resting period and keeps the trees vigorous enough to resist the fungi. Peach-scab (_Cladosporium carpophilum_ Thüm.) is a common and destructive fungus in peach-growing districts on the Atlantic seaboard and is found rather frequently in New York but seldom does much injury in the State. It appears in sooty, black spots and blotches on the surface of the peach, causing atrophy and hardening of the parts affected which, in severe cases, crack badly. Twigs and leaves may be affected. White-fleshed sorts suffer most and are ruined for the market even in mild attacks. Self-boiled lime and sulphur, if it does not wholly prevent infections, at least alleviates the trouble. Peach-growers in New York are much plagued by a mildew yet suffer small loss from it, though the disease greatly injures peach-foliage in some regions. The delicate, white or grayish powder, giving the name "powdery mildew," consists of the spores and mycelium of a fungus (_Sphærotheca pannosa_ (Wallroth) Léveillé) which attacks the leaves of several species of Prunus causing them to curl and crinkle and sometimes to drop. It occurs most often when there are sudden changes in temperature. When treatment is necessary, the self-boiled lime-sulphur mixture is used.