Among the common diseases and insect pests that attack the leaves and stems of potato vines are early blight, late blight, brown rot, the flea-beetle, and the potato beetle, or potato bug. Spraying with Bordeaux mixture to which a small portion of Paris green has been added will control both the diseases and the pests. The spraying should begin when the plants are five or six inches high and should not cease until the foliage begins to die. Scab is a disease of the tubers. It may be prevented (1) by using seed potatoes that are free from scab; (2) by planting land in which there is no scab; and (3) by soaking the seed in formalin (see page 135). SECTION XLII. OATS The oat plant belongs to the grass family. It is a hardy plant and, under good conditions, a vigorous grower. It stands cold and wet better than any other cereal except possibly rye. Oats like a cool, moist climate. In warm climates, oats do best when they are sowed in the fall. In cooler sections, spring seeding is more generally practiced. There are a great many varieties of oats. No one variety is best adapted to all sections, but many varieties make fine crops in many sections. Any variety is desirable which has these qualities: power to resist disease and insect enemies, heavy grains, thin hulls, good color, and suitability to local surroundings. As oats and rye make a better yield on poor land than any other cereals, some farmers usually plant these crops on their poorest lands. However, no land is too good to be used for so valuable a crop as oats. Oats require a great deal of moisture; hence light, sandy soils are not so well adapted to this crop as are the sandy loams and fine clay loams with their closer and heavier texture. If oats are to be planted in the spring, the ground should be broken in the fall, winter, or early spring so that no delay may occur at seeding-time. But to have a thoroughly settled, compact seed-bed the breaking of the land should be done at least a month before the seeding, and it will help greatly to run over the land with a disk harrow immediately after the breaking. [Illustration: FIG. 206. OATS Common oats at left; side oats at right] Oats may be planted by scattering them broadcast or by means of a drill. The drill is better, because the grains are more uniformly distributed and the depth of planting is better regulated. The seeds should be covered from one and a half to two inches deep. In a very dry season three inches may not be too deep. The amount of seed needed to the acre varies considerably, but generally the seeding is from two to three bushels an acre. On poor lands two bushels will be a fair average seeding; on good lands as much as three bushels should be used. [Illustration: FIG. 207. HARVESTING OATS]