Soil rot (Acrocystis Batatas) is injurious to young roots in dry seasons. The diseased part ceases to grow. Crop rotation and the application of kainit or sulfur at the rate of 300 pounds per acre are suggested remedies. Soft rot (Rhizopus nigricans) occurs in the storage house during the curing pro cess. If the potatoes are dry before storing it is not likely to be troublesome. Affected potatoes should be destroyed. Other diseases of little im portance are white rust, white rot, stem rot, dry rot, scab and leaf spot.
Among insects, sweet-potatoes are attacked by the weevil, plume moth, tortoise beetles, sawflies, cutworms, flea-beetles, crickets and tobacco worms [See Index]. The weevil (Cylas formdcarius) is a small bluish black insect that deposits its eggs in recesses at the base of the vine or at the upper end of the root. The white grubs burrow in the vine and down into the roots, which they destroy. The remedy is to feed or completely destroy all infested vines and roots. The plume moth (Piero phorus monodactylus) is a silver-brown insect bear ing black lines on the forewings. It is the larva of this that is destructive to sweet-potatoes by feeding on the leaves. The use of arsenical sprays
(one pound to twenty-five gallons of water) will control this pest. The larva is of a green color and bears a dark stripe along the middle of the back. Several kinds of tortoise beetles feed on the leaves soon after the plants are set. As a protection the plants may be dipped before setting in a solution of arsenate of lead, one pound to twenty-five gallons of water. Paris green of a strength of one-fourth pound to forty gallons of water, to which is added one-fourth pound of lime, is also effective. Flea beetles may be controlled by the arsenical treat ment, and sawflies by either the Paris green or the arsenical treatment.
Literature. • Wilcox & Smith, Farmer's Cyclopedia of Agri culture ; Bailey, Cyclopedia of American Horticul ture ; Fitz, Sweet Potato Culture ; Price, Sweet Potato Culture for Profit ; Farmers' Bulletins, United States Department of Agriculture, Nos. 26, 129 ; Arkansas Experiment Station, Bulletin No. 72 ; South Carolina Experiment Station, Bulletin No. 63. Numerous other publications can be traced through the Experiment Station Record.