Potatoes sometimes sport or "mix" in the hill, and these bud-sports may be treated as new varie ties. Practically all the new varieties of potatoes, however, are produced from seed, for every seedling is likely to be different from the parent. Seed-balls are not produced abundantly on most varieties. If it is desired to produce new kinds, the seed should be saved and treated as tomato seed is treated, being planted the following spring. The first year the plants are small and slender, and the tubers will also be very small. These tubers are saved and planted the next year, when a crop of good-sized tubers may be expected, showing their characteristics. If it is desired to combine features of two varieties, the flowers may be crossed ; and the resulting seed will produce hybrids.
Harvesting and storing.--Early potatoes are dug as soon as large enough for sale. Late varieties are left until the vines are dead ; should the vines be killed by blight and it is intended to store the tubers, the digging should be delayed, if possible, until ten days after the date the vines died. The grower should harvest when the land is dry, pick up the tubers at once and keep them cool. In stor age the tubers should he held between 32° and 40° Pahr., be well ventilated and kept dark.
Potatoes may be stored in the open, in piles covered with straw and earth, in cellars or root. houses according to the climatic conditions. In the northern states the cellar is the most advan tageous, since the conditions can be more easily controlled, and the crop may be inspected or sold at any time. The cellar should be kept dark. With sound tubers, the loss in weight in storage may vary between 5 and 20 per cent in the five winter months. Both temperature and the moisture con tent have an influence, a high temperature increas ing and a high moisture content diminishing the loss. Nobbe found that about 75 per cent of the depreciation is loss of the water content.
Enemies.
Diseases.—In the northern and north-central states the two most serious diseases are the early and late blights. The early blight (Alternaria solani) is a fungus which attacks the leaves, enter ing frequently through holes made by flea-beetles.
It comes on earlier in the season than the late blight and does not cause rot of the tubers. The late blight (Phytonhthora infestans, Figs. 750, 751, 752), another fungous disease, injures and often destroys the leaves, stems and tubers, and is prob ably familiar to most growers. These diseases
spread by means of spores which germinate on the potato leaves and stems and produce the fungus that causes the diseased appearance. If the leaves and stems be kept coated with some fungicide, as Bordeaux mixture, it prevents the germination of the spores and helps to check the spread of the disease.
Potato rosette attacks the stem, causirg the leaves to grow in clusters. It re duces the yield in many parts of the country. The disease is caused, in part at least, by Cortieium, vagum solani (Rhizoetonia solani).
One form of this fungus develops scale-like bodies on the tubers, causing the " black scale" of potatoes.
Scab (O5spora scabies) is a fun gous disease which appears on the tubers. For treatment, the seed tubers should be immersed for two hours in a solution of formalin of the strength of one pound of formalin to thirty gal lons of water. If the seed is not planted at once, it should be spread thinly to dry, and should be planted on scab-free soil.
Dry-rot (Fasarium oxnjspDruvi). —This disease attacks all parts of the plant below ground and produces a gradual premature death of the plants. Infected tubers rot and shrivel. This fun gus causes more or less loss to the potato crop in all sections of the United States.
A good and rather long rotation of crops is of value in combating all of these diseases.
In:yds.—The flea-beetle (Crepidodera [Epitrix] c.cumeris) attacks the leaves, puncturing them and thus furnishing an easy entrance for spores of dis Spraying w;th Bordeaux mixture as soon as the insects appear is of value. It acts as a deterrent. On the Pacific coast other flea-beetles occur, and for such the use of arsenites alone or in Bordeaux mixture is advised.
The potato-hug or Colorado potato-beetle (Do ryphora dccemlineata, Fig. 753), the larva of which attacks the foliage, is destroyed by spraying with Paris green or some other arsenite in a solution, preferably Bordeaux mixture, using one-fourth to one-half pound of Paris green to fifty gallons of solution, and applying 150 to 200 gallons per acre when the foliage is well grown.
The old-fashioned potato-bug or blister-beetle (Epicaula rittata) is combated in the same way as the Colorado potato-beetle. It is now rarely seen. The potato-worm (Gelcchia operculella) is injurious on the Pacific coast. The potato-stalk weevil (Tricho kris trinotata) attacks the stems. It is found from Canada to Florida.