20 Farmers Bulletin 1126.

DISEASES OF SUDAN GRASS.

RED-SPOT.

The worst disease of Sudan grass is the so-called sorghum blight,7 more appropriately designated as red-spot. This is a bacterial disease, characterized by the appearance of distinct reddish spots on the leaves, which gradually spread until the leaves turn brown and die. Its effect on the plant is much the same as rust, and like rust it is most destructive in warm, humid regions. It is prevalent in the Great Plains, but does little damage there except in wet seasons. Along the South Atlantic and Gulf coasts it almost entirely prevents the profitable production of Sudan grass. (See map, fig. 3.)

No remedy or preventive of red-spot has been found other than the use of resistant varieties. Eotation with other crops not subject to the disease probably holds it in check. In localities where sorghums are regularly grown, however, they furnish a continuous source of infection.

KERNEL SMUT.

Sudan grass is subject to the kernel smut of sorghum. This disease changes the individual kernels into a mass of dark spores covered by a grayish membrane. These spore masses look like an elongated seed, fully twice as large as the healthy kernels.

As in the case of red-spot, the sorghums furnish a source of infection for the kernel smut. This disease of the seed is not of any great importance in the production of Sudan grass for hay and pasture.

Kernel smut can be controlled very effectively by treating the seed with formaldehyde.8 One pound of full-strength formaldehyde is mixed with 30 gallons of water. The sacks of seed are immersed for one hour in this solution, which should be stirred occasionally. Then the sacks are taken out and drained, after which the seed is spread upon a clean floor or canvas to dry. When dry the seed can be sown, but care must be used to see that, after the treatment, it does not come in contact with an smut-infected sacks. Such seed treatment is profitable only for sowing fields intended for seed production.

INSECT ENEMIES OF SUDAN GRASS.9 GRASSHOPPERS.

In parts of the United States where grasshoppers are abundant they do considerable damage to Sudan grass. These grasshoppers are chiefly native species which hatch out in the vicinity. The cultivation of fields and fence rows late in the fall or in early winter destroys large quantities of the eggs and helps to keep these pests in 7KeIIerman, W. A., and W. T. Swingle. Sorghum blight. In 1st Ann. Rpt., Kans. Agr. Bxp. Sta., 1888, p. 281-302. 1889.

Burrill, T. J. A disease of broom corn and sorghum. In Proc. 8th Ann., Soc. Prom. Agr. Sei., 1887, p. 30-36. 1887.

Radais, Maxima On the blight of sorghum. In Bot. Gaz., vol. 28, no. 1, p. 65-68. 1899. 8 Humphrey, Harry B., and Alden A. Potter. Cereal smuts and the disinfection of seed grain. U. S. De'pt. Agr., Farmers' Bui. 939, 28 p., 16 fig. 1918. 8 This discussion of insects was prepared with the advice and cooperation of W. R. Walton, Office of Cereal and Forage Insect Investigations, Bureau of Entomology, United States Department of Agriculture.