p n. y ; 
 
 or 
 
 . 
 
 Issued Junuarj 27, 1910, 
 
 U. S. DEPARTMENT OF AGRICULTURE 
 
 BUR] Ai 0] PLAN I INDUSTRY Circular No. S 
 B. I . GALLOW W, • 
 
 r P 
 
 TILE S.MITS OF SORQHUM. 
 
 EDWARD M. FREEMAN, Pathologist, 
 
 HARRY J. C. UMBERGER, Scientif* Assistant, 
 Office of Grain [Investigations. 
 
 21336 in 
 
 WASHINGTON : GOVERNMENT PRINTING Orrif 
 
 
[Cir. 8.] 
 2 
 
 BlREAl OF PLANT INDUSTRY. 
 
 Bureau, Beverly T. Galloway. 
 : ( Mefof Bureau, Albert F. Woods. 
 Editor, J. E. Rockwell. 
 ' Urk, James E. .!• 
 
CONTENTS. 
 
 [ntroduetion 
 
 Kin hum smuts 
 
 Grain I - 1 1 1 1 1 1 il 
 
 Treatn rain smut. . <; 
 
 Formalin treatmenl <; 
 
 Hot-water treatmenl 7 
 
 Copper sulphate treatmenl 7 
 
 Head smul > 
 
 ns g 
 
 Cir.8.] 3 
 
Digitized by the Internet Archive 
 in 2013 
 
 http://archive.org/details/smutsoOOunit 
 
B. II : i 
 
 THE SMUTS OF SORGHUM: 
 
 INTRODUCTION. 
 
 The smuts are among the most destructive enemies of sorghums. 
 It 1 1 1 ; i \ be thai the actual loss from smut in these highl} importanl 
 crops is not at presenl as serious as that sustained by oats and wlieat, 
 but it is nevertheless quite considerable and is certainly serious in 
 some localities. The chief danger from these smuts is the probabil- 
 ity of their rapid spread if proper precautions are not taken to hold 
 them in check. The area where sorghum crops are grown is being 
 rapidly extended, and with this extension the smuts may easily be 
 distributed over nevs areas. I>\ using simple precautions al the pres- 
 enl time, farmers may avoid much disappointment and loss in the 
 future. The losses caused by smuts of oats, barley, and wheat 
 throughout the United States oughl to prove a sufficient warning 
 to all farmers and communities which are now either growing or in- 
 troducing sorghum crops, because the smuts of sorghums may yet 
 i -a u-e as much damage as t hose of the other cereals mentioned. 
 
 The objects of this circular are (1) to call attention to these danger- 
 ous pests, (2) to w a rn farmers of the danger of introducing t hem into 
 new localities, and (3) to suggest simple methods of getting rid of 
 them if they ,ne already present. 
 
 KINDS OF SORGHUM SMUTS. 
 
 There are in this country two well-known smuts of sorghums: The 
 grain, or kernel, smut (SpTiacelotheca sorghi (Link) Clinton) and the 
 head smut (Sphacelotheca reiliana (Kuhn) Clinton). 
 
 The grain, or kernel, smut is easily distinguished by the fact that 
 "id\ the individual kernel-, or grains, are affected, while the head 
 retains its usual form and nearly its usual appearance. Most, if not 
 all, of the kernels in a smutted head are usually destroyed. Each 
 kernel is changed into a more or less conical, grayish to reddish mass 
 containing the dark-colored smut dust, or spore-. 
 
 The head smut is very different in appearance. The whole head. 
 just as it emerges from the upper leaf, is converted into a single huge 
 smut mass, covered by a whitish or grayish membrane, which soon 
 
 " rn recenl years there has been a \ cry rapid settlement of the semiarid lands. The 
 Borghums are among the most suitable crops for cultivation on such lands, and many 
 inquiries are received by iliis Bureau for information in regard to the sorghum smuts. 
 The first edition of Circular No. 8, on these smuts, is exhausted. This revised edition 
 ictical knowledge of these disi isi and alt > such improvements in the li"t- 
 water treatment for the grain Bmul as are a<l\ isable in the lighl of further investiga- 
 tions. B. T. ( I \l I OW \ i , 
 
6 THE SMUTS OF SORGHUM. 
 
 bursts .-Hid sots the spores free. In this smut, therefore, all trace of 
 the individual grains, or kernels, is lost. The smut mass resembles 
 somewhat in appearance a smut mass on corn. 
 
 It is not yet known how many of the various groups and varieties 
 of sorghum each smut infects. The grain smut occurs on all of the 
 principal groups, while the head smut has been observed on sorgos 
 (sweet sorghums), kalirs. and shallu. Neither smut has been ob- 
 served on milo up to the present time, and attempts to inoculate milo 
 with the kernel smut of kafirs ami sorgos have proved unsuccessful. 
 
 GRAIN. OR KERNEL, SMUT. 
 
 Of the two smuts of sorghum, the kernel smut is at present the more 
 widely distributed. It is found almost universally where sorghum 
 crops are grown. The losses sustained are in many districts very 
 severe. They are increasing and will continue to increase unless pre- 
 ventive measures are adopted. 
 
 The life history of this grain smut is now well known. It is similar 
 to that of stinking smut, or bunt, of wheat, viz, the spores, or smut 
 dust, get on the kernels in thrashing or in handling, and when the seed 
 is planted they grow at the same time that the seed sprouts. The 
 smut plant penetrates the stalk of the young seedling plant and grows 
 inside of the latter until the heads are formed, when the fungus 
 forms its spores inside of the grains, replacing the latter. 
 
 As in the bunt of wheat, careful seed treatment will kill the smut 
 spores, because the latter cling to the outside of the seeds, and after 
 such treatment the crop will be free from smut. 
 
 It is therefore very important that any farmer who is not sure that 
 his seed is free from smut should treat his seed in one of the ways 
 suggested in this circular. When his seed is once clean he can keep 
 his farm free from smut by raising his own seed, provided he does not 
 allow it to become smutted again in a smutty thrashing machine or 
 in the subsequent handling of the grain. 
 
 TREATMENT OF GRAIN SMUT. 
 
 Seed that is smutty may lie t reated in the following ways: 
 
 FORMALIN TREATMENT. 
 
 Mix 1 pound of full-strength formalin with 30 gallons of water. 
 Put the seed in sacks and immerse the sacks in this solution for one 
 hour, stirring ii occasionally. Then take the sacks out and set them 
 to drain. Spread the seed out on a clean floor or canvas. He sure 
 that all of the sacks, the bain floor, and the canvas used in handling 
 the grain after t real ment are cleaned either with boiling water or with 
 a strong formalin solution. The seed will be infected again if any 
 untreated smut spores touch it. When the seed is sufficiently dry 
 
 after t real ment it may be sown. • 
 [Cir. 8.] 
 
THE SM I' is i GHUM. 
 
 The same solution ma} also be used us a spnn . in which case the 
 seed to be i reated should be spread oul on a clean floor or i-mw as and 
 sprinkled with the solution. It must be shoveled over frequently 
 until all of the seeds arc wet. U ma\ then be shoveled into a pile 
 and left over night, covered with a clean canvas or sacking to keep 
 in the fumes, and then spread oul to drj in the morning. Seed 
 treated in this way will be free from smut. The immersion method 
 is more thorough, but is not as convenient as the sprinkling method. 
 
 IIOT-W A 111: rREATM INI. 
 
 Hot water is a most cheap and efficient means of treating sorghum 
 seed. The I real n km 1 1 is more easily applied to sorghum than to wheat 
 and barlej . because sorghum seeds (at least those of kafirs and sorgos, 
 or sweet sorghums) will stand much higher temperatures than wheal 
 and barley seeds. The smaller quantity of seed used to the acre in the 
 sorghum crops is an additional advantage, making it possible to treat 
 easily all the seed required for a large area. In the hot-water treat- 
 ments of sorgo and kalir a I'airU wide range of temperature is per- 
 missible, and the operation is therefore easily performed on the farm. 
 
 In brief, the process is as follows: Heat two large vats or tubs of 
 water to aboul 135 and 140 F., respectively. Place the seed to be 
 treated in a clean sack or wire basket and plunge it into the tub of 
 water heated to 135 P. for a moment. Then transfer the sack to the 
 second tub or vat for ten to twelve minutes. Keep the temperature 
 of the water in the second tub between 134 and I III I''. It should 
 QOl be allowed to go above 1 12 or below 134 V. The seed .should 
 
 be frequently stirred in order to keep the temperature uniform 
 throughout. Small sacks should be used, since in large sacks it is 
 impossible to keep the temperature constant. After this treatment 
 eed is spread out to dry on a clean floor or canvas. When suffi- 
 cient l\ dry it may be sow n. 
 
 A.S in the formalin treatment, ever} precaution must be taken to 
 prevenl infection of the seed after treatment. Although this treat- 
 ment is not as convenient as the formalin method, it is just as effi- 
 cient, is cheaper, and. on account of the wide range of temperal ure, is 
 easily applied. It is superior to the formalin method in that the 
 farmer docs not have to rely on a druggist for the strength of a forma 
 lin solution. If the formalin is not of full standard strength (i. e., a 
 10 per cenl solution), the formalin treatment ma\ not be successful. 
 In the hot-water treatment all of the implements and materials are 
 directly under the control of the fanner. 
 
 COPPER st I. I'll VI I I i;i \ I \i I \ i 
 
 Solution- of copper sulphate (bluestone) also give satisfactory 
 results, but are certainly no better than, and probably not even as 
 good as, the two methods described above. 
 
 [Clr. 8.] 
 
8 
 
 THE SMUTS OF SORGHUM. ? == ht 
 
 HEAD SMUT. i^=<3) 
 
 = CM 
 
 At present the head smut does not occur in abundance beyond a o 
 very restricted area in the Panhandle of Texas. Its life history is £_. 
 not yet understood, but enough is known to show that the treatments *rao 
 recommended for the grain smut have absolutely no effect upon the 1=^ 
 head smut. This indicates that this disease may be more difficult ^|gj 
 to control than the grain smut when once it succeeds in getting a fair = 
 
 start. 
 
 The only recommendation that can be made at the present time is 
 to keep the smut away from the farm and the community. In order 
 to do this the farmer must be sure that his seed did not come from a 
 crop that contained head smut, If it is allowed to spread unchecked, 
 it bids fair to become troublesome in the future. In case it is already 
 present on the farm the infected plants should be cut out completely 
 and burned before the smut spores have a chance to scatter. 
 
 RECOMMENDATIONS. 
 
 The precautions necessary and the proper treatments for the smuts 
 of sorghum crops may be summarized as follows: 
 
 (l) & If possible, get seed free from smut— from fields that are 
 known to have had no smut during the preceding year. Also be sure 
 that such seed has not become smutted in harvesting and handling 
 
 (2) Keep your farm free from smut by using your own seed and 
 employing only machinery that will not contaminate your crop. 
 
 These first two precautions will insure you against both kinds ot 
 
 smut, .„ 
 
 (3) Treat your seed with either formalin or hot water it you are 
 not sure that it is free from smut. This will not necessarily insure 
 the farm against head smut. 
 
 (4) Maintain a quarantine against any locality or hum wtiere 
 smut is known to exist, as well as against any seed grower who allows 
 smut in his fields. This course will largely prevent the spread ot 
 
 both kinds of smut. 
 
 (5) Maintain a quarantine against any handlers of machinery who 
 allow their machinery to become or remain contaminated with smut 
 spores. This would be effective against the gram smut. It would 
 probably have no effect on the head smut, however. 
 
 (6) Milo has not yet been reported as subject to either smut, and 
 hence may probably be safely grown without treatment. 
 
 Approved : 
 
 James Wilson, 
 
 Secretary of Agriculture. 
 
 Washington, D. C, April 22, 1908. 
 
 [Cir.8.] \~