6 BULLETIN 1116, U. S. DEPAETMENT OF AGRICULTURE. 



Alternaria producing the seedling leaf -spot and seed injury in 

 Louisiana. 



Eice infected with the various forms of fungi which produce fleck- 

 ing and decay germinates very poorly as compared with uninfected 

 seed. The germ often is killed by the invading parasite (Pis. II and 

 III, A) . Wet soils, which tend to check the normal germination and 

 development of seedlings, seem to favor the growth of the fungus, 

 and the seed may be destroyed and a poor stand result. Seed treat- 

 ment before sowing would not eliminate injury done by these fungi 

 previously, but might prevent further injury and prevent the spread 

 of these organisms. Seed of Honduras rice obtained from California, 

 where seed-infesting fungi are rare, and sown in Louisiana germinated 

 better than seed of the same variety grown in Louisiana (Tables 2 

 and 4) . The difference in the percentages of germination is an 

 indication, perhaps, of the extent of damage commonly caused to 

 seed rice in Louisiana. Of course, if the number of these fungi 

 which may be carried in the soil was considered, the damage might be 

 greater. Treated seed from the same lot germinated almost 2 per 

 cent better than untreated seed. The soil where this seed was 

 sown was in very good condition. The seed was sown late and had 

 almost ideal conditions for germination. This gave the untreated 

 seed an opportunity to germinate before much injury could be done 

 by the fungi carried internally. 



SEED TREATMENT. 



Upon undertaking a seed treatment it was soon found that sur- 

 face sterilization was of no value. Seeds were dehuUed and treated 

 for 3 minutes in 50 to 70 per cent alcohol and then soaked for 10 

 minutes in bichlorid of mercury solution (1 to 1,000) with no effect 

 (Pis. IV, A; V; and VI, A). Godfrey^ treated dehuUed seed by the 

 Jensen modified hot-water method and found that the sclerotial form 

 was killed. Dehulling the seed, of course, would not be at all prac- 

 ticable, so an attempt was made to find out to what extent, if at all, 

 hot water could be used for treating rice in the hull. It was found 

 that practically all the fungi in the seed could be killed without 

 injury to the seed germ if care was exercised in carrying out the 

 treatment. 



Rice, which has close-fitting, tough glumes, requires a much longer 

 presoaking in tepid water and a more extended soaking in hot water 

 than the other small grains. The best method found was to pre- 

 soak the seed overnight in water which was somewhat warm to 

 begin mth, and hence more effective than cold water, and then, 

 subsequently, to treat the seed with hot water. Before beginning 



6 Godfrey, G. H. Op. cit. 1920. 



