The fungus that causes early blight of potatoes (_Alternaria solani_ (E. & M.) J. & G.) occurs on tomatoes also, sometimes doing much injury. The spots formed are at first small and black, later enlarging and exhibiting fine concentric rings. A somewhat similar leaf-blight results from a species of _Cylindrosporium_, and other fungi may occur on diseased leaves. =Leaf mold= (_Cladosporium fulvum_ Cke.) is quite distinct from the foregoing in appearance. It does not cause such distinct spots but occurs in greenish brown, velvety patches of irregular outline on the under side of the leaves. The lower leaves are first attacked, and as the disease progresses they turn yellow and drop off. This is the principal fungous enemy of greenhouse tomatoes, but also does injury in gardens, particularly in Florida and the Gulf region. It is readily controlled by spraying. In the greenhouse care should be taken to ventilate well, without, however, allowing cold drafts to strike the plants. =Downy mildew= (_Phytopthora infestans_ DeBy.), the cause of the late blight of potatoes, will attack tomatoes during cool and very moist weather, which greatly favors its development. Such outbreaks sometimes occur to a limited extent in New England and serious losses are reported on the winter crop in southern California, but the disease has never been troublesome in other sections of the country, as it cannot develop in dry or hot weather. It affects the tomato as it does the potato, forming on the leaves dark, discolored spots, which spread rapidly under favorable conditions, killing the foliage in a few days. The fruit is also attacked and becomes covered with the mildew-like spore-bearing threads of the fungus. Bordeaux mixture properly applied is an efficient preventive. =Spraying tomatoes.=--It should be the invariable practice of the tomato grower to spray with Bordeaux mixture to prevent injury from any of these leaf-blights. This should be done while the plants are still healthy, as if put off until the disease appears the battle is half lost. Make the first application to the young plants in the seed-bed a few days before transplanting. Spray again within a week after the plants are set in the field, and repeat at intervals of ten days or two weeks until the fruit is full grown. Success in spraying depends mainly on the thoroughness of the work. The aim should be to cover every leaf with a fine mist. Do not drench the foliage but pass to the next plant before the drops run together and off the leaf. Use a nozzle that gives a fine spray and maintain a high pressure at the pump.