On the death of the rye plants the eelworms mostly travel back to the soil, but sundry eggs and larvæ stop in the dried-up remains. Rye straw may further infect a diseased field by getting into farmyard manure and being brought back again with it; for the eelworms (at any rate as eggs and larvæ) are killed neither by drying nor by the action of dung and other decaying substances. Strongly infected spots (bare patches) on an infested field are usually the places where dung containing diseased rye-straw has lain for some time. From such centres the spreading of the eelworms takes place: (1) _actively_ by the migration of the worms, (2) _passively_ by rain, the feet of labourers, the hoofs of horses, field implements, etc.; also (on loose soils) by the wind, which not only blows about particles of earth, but also the dried-up larvæ which are always found on the surface of the ground. As the eelworms multiply very rapidly whenever they are in the plants, and as the means of distribution are very numerous, the disease spreads with great rapidity. _Remedies._—Proper rotation; limitation of the culture of rye, growing in place of it carrots, turnips, or lupines. Now and then (but not too frequently), potatoes, buckwheat, clover, and oats may be cultivated in the fields affected, at any rate before sowing rye again. Abundant manuring, especially with sulphates of potash, ammonia, and iron. Deep cultivation of the soil, since the eelworms find no food in the deeper, damper layers of the soil, nor can they pass into the dried condition, and so must die. =Oats= suffer from eelworms just in the same way as rye. =Clover Sickness= is marked by short stunted shoots, and whitish rounded buds, often remaining closed; also by the whitish colour and abnormal thickening of the shoots and buds. =Eelworm Disease of Potatoes.=—Crumpling and small growth of the parts above ground. In many cases there may even be no potatoes at all, or only small ones, poor in starch, though sometimes they may be tolerably large. On the surface of the tubers there are discoloured rotten spots, not penetrating deeply, and usually (but not always) at the attached end. These dark patches contain the eelworms. =Eelworm Disease of Buckwheat.=—Joints of the stem for the most part much thickened, but abnormally short. In many cases a large amount of branching in the lower part of the stem, usually at a place where it bears a nodular swelling. Branches generally short. There may be twists and bends in the stem and branches. Often, but not always, the formation of flowers and fruit is stopped. The thickened parts of the stem are brittle; they contain the eelworms in their interior. The =Wheat Eelworm= (_Tylenchus scandens_ = _T. tritici_). [Illustration: FIG. 133.—Ear Cockles of Wheat; the third shows the eelworm larvæ on its cut surface. ]