It is very apparent that some varieties are more subject to the attacks of diseases than others. The Big-Stem Jersey and the Jersey group generally are especially subject to disease, while varieties of the Hayman group, such as Southern Queen, are seldom affected.

The sweet potato is reasonably free from the ravages of insects. Cutworms frequently destroy the young plants after they are set in the field, especially when the land has been in grass the previous seafson. The sweet-potato borer, which works in the roots, is widely distributed and causes considerable injury in the Gulf Coast States. A small insect known as thrips works on the under side of the leaves during the hot and dry weather of midsummer, but as a rule the real damage caused by this insect is slight.

The harvesting and marketing of sweet potatoes direct from the field begin about the middle of August and continue until the crop is all disposed of or placed in storage for winter marketing. During the early part of the harvesting season the yield is light, but as a rule the prices paid are good. The supply for home use and those potatoes that are to be kept in storage should not be dug until just before frost. In the localities where frosts do not occur until quite late in the season the sweet potatoes ripen and the vines show a slight tinge of yellow when ready for handling.

The foliage of the sweet potato is very tender and is easily injured by frost. A light frosting of the leaves will do no harm, but should the vines become frozen before digging they should be cut away to prevent the frozen sap passing down to the roots and injuring them.

In sorting sweet potatoes preparatory to packing, about four grades are recognized - i. e., fancy, primes, seconds, and culls. Those packed as fancy include only the most select, both in size and shape. The primes include all those adapted to general first-class trade, while the seconds include the smaller and more irregular stock which goes to a lower-priced trade. The culls are not marketed unless good stock is exceedingly scarce, and as a rule are used for feeding to hogs.

Sweet potatoes are usually shipped in barrels holding eleven pecks each. Some markets require that the barrels be faced and headed, while for others the tops are slightly rounded and covered with burlap. Small lots of extra-fancy sweet potatoes are sometimes shipped in one-bushel crates having raised tops; also in patent folding crates. Throughout the process of handling care must be exercised to see that the sweet potatoes do not become bruised, for upon this their shipping and keeping qualities greatly depend.

Unlike most perishable products, the sweet potato requires warmth and a dry atmosphere while in storage. The method of storing will depend both upon the locality and the quantity of potatoes to be cared for. The temperature and conditions of a rather cool living room are admirably adapted for keeping sweet potatoes intended for home use in the North, while in the South they may be placed in pits or stored in outdoor cellars. The home supply may be placed in crates and stored in a loft over the kitchen part of the dwelling. Sweet potatoes should not be stored in bags or in barrels without ventilation.

Where large quantities of sweet potatoes are stored for winter marketing, the method employed in the Southern States is to place them in outdoor pits and cellars, while at the North some form of heated storage house will be required. Whether the storage be in pit, cellar, or house, a dry, warm atmosphere with ventilation is essential to good keeping.

Of the large number of varieties of the sweet potato there are not more than ten that are now of great commercial importance in the United States. For the markets that require a dry, mealy-fleshed potato those varieties belonging to the Jersey group are suitable. For the Southern trade and where a moist-fleshed potato is desired those commonly designated as yams are in demand. Among the Jerseys that are extensively grown are the Big-Stem Jersey, the Yellow Jersey, and the Red Jersey. The principal varieties of the yam group are the Southern Queen, the Pumpkin Yam, the Georgia, the Florida, and the Red Bermuda. Of the varieties mentioned there are a large number of special strains known under many local names.

In the selection of varieties for home use one must be governed largely by locality. As a rule those of the Jersey group will thrive farther north than those of the so-called yam types. For market purposes the particular variety or strain grown in the vicinity should first be selected, and afterward other varieties may be experimented with in a small way.

The following brief descriptions of a few of the leading varieties may be of assistance in selecting those best adapted to various conditions of soil and climate:

Big-Stem Jersey

This variety is the most popular among growers who are supplying the Northern and Eastern markets. It is a form of the Yellow Jersey, having been selected for its productiveness and dry, yellow flesh. The vines are slender and long; the potatoes are of spindle shape and inclined to grow rather large; color of potatoes yellow; color of flesh light yellow or deep cream. While this variety yields heavily, it is unfortunately a rather poor keeper, and its flesh is inclined to become dry and 'punky' toward spring. It will thrive well toward the north, but is better adapted for use as a commercial variety than for home consumption.

Southern Queen, Or Hayman

The vines of this variety are strong and vigorous; the potatoes are large, thick, and blunt at ends or of short spindle shape; the color is white or light cream, while the flesh is of cream color, becoming darker in cooking, moist, and very sweet. This variety is most extensively grown for market purposes where a sweet, moist-fleshed potato is demanded. The Southern Queen yields well, is an excellent keeper, and is adapted for both marketing and stock feeding and for home use in the South Atlantic and Gulf Coast States, but it does not mature when grown in the extreme North.

Red Bermuda

The Red Bermuda vines are large and vigorous. The potatoes are usually large and overgrown with heavy ridges and veins. The color of the potatoes is rose red; flesh, creamy; quality fair but not so sweet as Southern Queen. This variety is a heavy cropper and suitable for feeding to stock. It is one of the few so-called yams which thrive in the northern portion of the sweet potato area.

Black Spanish, or Nigger Choker

Black Spanish, or 'Nigger Choker.' - The Black Spanish vines are very long, vigorous, and dark purple in color. The potatoes are long, cylindrical, crooked, or bent; dark purple in color, with snowy white flesh and poor quality. This variety is grown mostly for stock feeding.

Shanghai

The vines of the Shanghai variety are large and vigorous; the potatoes long, cylindrical; the outside color almost white. The flesh is creamy white, becoming darker in cooking. When baked the flesh is somewhat dry and mealy and the flavor rather poor. This variety yields fairly well and is adapted for use as stock food in the Gulf Coast States.

The cost of growing an acre of sweet potatoes will vary with the cropping plan and the extent to which the crop is grown. On an average the cost of growing an acre of sweet potatoes in the regular commercial district is about as follows: Rental of land, $8; plowing and fitting, $5; fertilizers, $20; 10,000 plants, $10; planting, $5; cultivating, $5; digging and marketing, $25; total, $78. An average yield of sweet potatoes is at the rate of one barrel to 100 hills, or 100 barrels to an acre. The price per barrel paid the grower is seldom less than $1.25, and $2.50 or $3 is not uncommon. During good seasons the net profit from one acre of sweet potatoes is about $75. While occasionally the net returns are from $100 to $150 an acre for a single season, there are seasons of crop failure or overproduction when very little, if any, profit is realized.

The sweet-potato growers on the eastern shore of Virginia as a rule plant about ten acres in sweet potatoes, and this constitutes their money crop. The remainder of the cleared portion of their small farms is devoted to corn, pasture, and hay, all for home use. Here the sweet-potato crop is grown almost entirely without the aid of hired help, and the cost of production does not exceed $40 an acre. Where the crop is stored the gross returns are greater, but the cost of production is increased proportionately."