Beets are subject to a leaf-spot. This causes small, round, dead spots to appear on the leaves. Bordeaux mixture applied as soon as the spots appear and at intervals of one or two weeks will check this disease.
Cabbage.—Clubroot is a disease which causes the roots of cabbage, cauliflower, kohlrabi, and allied plants to become swollen and deformed, and prevents them from functioning properly. If it is not noticed at transplanting-time the first indication of its presence is the sudden wilting of the plants. All affected plants should be destroyed. The seedbed and that part of the garden where the cabbages are to be planted should be limed two or three months before planting. Use between fifty and sixty pounds of air-slaked lime on a plot twenty by twenty feet, and thoroughly mix it with the soil.
Corn.—Corn smut usually appears as swellings, covered with a silvery membrane, on the tassels or ears. These break open later and disclose the masses of dark-colored spores. The swellings should be cut off and destroyed before they burst.
Cucumber.—Anthracnose, angular leafspot, and downy mildew are diseases attacking the leaves of cucumbers which can be controlled to some extent by frequent spraying with Bordeaux mixture. This should be applied as soon as the diseases are noticed and repeated at intervals of one or two weeks.
Peas are affected by a mildew which shows itself on the leaves and pods as a whitish mold. The plants should be dusted with powdered sulphur, or sprayed with potassium-sulphide solution to which resin fish-oil soap has been added to make it stick to the leaves.
Potato.—Two important diseases affecting potatoes are scab and late blight. The former is a disease which lives in the soil and is also carried over on infected potatoes. It shows itself as scabby spots on the tubers. Seed potatoes can be disinfected by soaking them, before they are cut, for two hours in a solution of one part Formalin to two hundred and forty parts water. This treatment will not prevent scab if the soil is already infected. An alkaline soil favors the growth of this disease.
Late blight appears late in the season and causes the leaves to blacken, become watery, and decay, often accompanied with an offensive odor. The disease also penetrates the tubers and renders them unfit for storage purposes. Spraying with Bordeaux mixture is practised as a preventive measure. It should be applied when the plants are six inches high, and repeated at intervals of about ten days until the crop is mature. Crops can be obtained without spraying, but Bordeaux mixture may be considered as a form of insurance. Lead arsenate may be added to the Bordeaux mixture if potato-beetles are present.
Tomato.—Tomato leaf-spot is a disease which causes dark-brown spots to appear on the leaves. The areas attacked shrivel and die. Spray with Bordeaux mixture.
It is just as important to apply remedial or preventive measures early in the case of diseases as it is in controlling insect pests. Fine mist-like sprays should be used as recommended for applying stomach poisons, and for the same reason.