The plants will thrive in the cooler tropics and even in the colder temperate regions; in moist and dry climates; and on many kinds of soil. But the mild-temperate regions, fairly dry climates and light loamy soils generally suit them best. Such produce earlier, mealier, more highly flavored potatoes than the other conditions. While Americans demand potatoes of this order, Europeans seem generally to pre fer the harder, less mealy tubers, produced in cloudy climates and upon rather rich, moist loamy soils. The soil should be well supplied with organic matter, but this should not be added fresh in the form of stable manure. Such applications should be made to a Previous crop, such as corn, since practice has shown that the quality of the crop is thus improved. Generous applications of commercial fertilizers should be given. Dried blood, sulphate of potash, super phosphate, ammonium sulphate and wood ashes are favorite fertilizers for this cron. The amounts to apply will depend largely upon the character and quality of the soil. The plowing should be as deep as the surface soil will permit, six inches or more. It should be done as soon as the weather becomes settled. The ((seed" is dropped at intervals of 12 to 18 inches in rows about 30 inches apart. Generally this is done by hand in a furrow about four inches deep, but upon a large scale potato planting machines are used. These machines make their own furrows, sow the fertilizer, drop the ((seed* at regular intervals, cover the row and mark the position of the next row.
Before •the young plants appear a weeder is run over the field once or perhaps twice to keep the surface loose and to destroy spouting weeds; after the plants are up the cultivator is used between the rows until the vines cover and shade the ground. Flat cultivation is in general vogue, but ridging or billing has its advocates, who claim that the practice dries and warms the soil, thus hastening maturity, and that the young potatoes are less likely to be exposed to the sun and thus become green. When the tops begin to turn yellow the tubers may be dug; but late kinds, which are generally planted three or four weeks later than the earliest crops and about two inches deeper, are allowed to remain in the ground until the vines have died or until the weather becomes cold in the autumn. The num ber of cultivations varies from a minimum of three for the earliest crops, to a maximum of eight or sometimes more for the late. Hand digging is usually practised upon small farms; a specially made plow is also often employed; but upon large plantations machines which sift the tubers from the soil and leave them at the surface are in common use. In the South a second crop of potatoes often follows the first in the same season; in the North the land occu pied by early potatoes is often planted to winter wheat ; that occupied by a late crop is left bare until spring when cereals frequently are sown. Potatoes are favorite crops for preparing the land for such crops as strawberries, raspberries and other small fruits, truck crops, etc.
Insects.— Among the insects which feed upon the potato are tortoise blister and flea beetles. The three-lined potato beetle (Lema trilineata) and the tomato worm (Sphinx are also frequently seriously troublesome. The most widely destructive enemy, 'however, is probably the potato-bug or properly the Colorado potato beetle (Doryphora decemlsneata). Unlike most insect pests this beetle became troublesome first in the West and migrated eastward. When the potato was first cultivated in the West this insect left its original food plant the sand-bur (Solanum sostratunt), and traveled from field to field, living upon potato vines. In 1860 it had become troublesome in Nebraska; in 1870 it was busy in Ohio and Ontario; and in 1875 it was well known in the Atlantic States as far south as Virginia. Its spread in the South has been less rapid probably because the potato is there less extensively grown than in the North. The hibernating adults appear in the spring and lay yellow eggs in clusters upon the foliage, sometimes even before it appears above the surface. In about a week the red larva appear, eat ravenously for about three weeks, pupate for about 10 days and emerge for feeding and egg-laying. From two to five broods appear in a season. This insect has a number of enemies, but farmers prefer to depend upon Paris green or other arsenates which are sometimes applied as a dust while the dew is on the plants, but usually as a spray. This is also more or less effective for the other species mentioned above.
Two stalk-borers are often troublesome; one, the larva of an owlet moth (Gortyna nitela), the other of a beetle (Trichobaris trinotatus). Wilting of the vines is generally the first indication of their presence and the only remedy recommended is the burning of the vines as soon as observed to be wilting.
Two so-called plant diseases are reported troublesome in the North; early blight naria solani) and late blight or rot (Phy tophthora infestans). In the South Bacillus sol anacearum is believed to be the cause of the brown rot. These three maladies are character ized by the destruction of the plants and are thought to be spread by insects which feed upon thP foliage. Hence the remedies most in vogue arc the control of the insects and the use of Bordeaux mixture, Paris green, and Pyrox. Care in selecting ((seed* potatoes from non infected districts and rotation of crops, the potatoes being moved to fresh soil each year, are also recommended. The scabbiness of tubers is thought to be prevented by soaking the in a solution of formalin or of corrosive sublimate, and by rotation of crops.
Consult Gilbert, A. W., 'The Potato) (New York 1915); Grubb, E. H., and Guilford, W. S., 'The Potato) (ib. 1912) ; Riley, C. V., 'Potato Pests' (ib. 1876) ; Smith, J. B., 'Economic entomology' (Philadelphia 1896) ; also bulletins of the United States Department of Agriculture and of the State Agricultural Colleges.