NEMATODE DISEASE OF WHEAT. 33 



The writer has also separated nematode galls from small quanti- 

 ties of diseased wheat by another method, which requires considerable 

 care and effort for its successful execution. It is carried out by re- 

 leasing water under pressure at the bottom of a receptacle which 

 contains the infected wheat and stirring and roiling vigorously at 

 the same time. If the water is released through a hollow rod at- 

 tached to a hose the rod may also be used in stirring the grain. 

 With such treatment the nematode galls and other light material 

 will rise to the surface and may be easily removed. Whether this 

 water method would be effective for use where large quantities of 

 grain are to be separated has not been determined. 



In removing the galls by either of these means there is little likeli- 

 hood that seed so cleansed will bear any living larvse on the surfaces 

 of the kernels. Only rarely do the larva? escape from galls which 

 are held under the usual storage conditions, and any that might es- 

 cape would most likely be killed by the usual rubbing together of 

 the kernels as the grain is handled. On drying out, the larvse become 

 stiff and brittle and are very easily broken. However, in order to 

 eliminate the possibility of transmitting any source of infection 

 along with the sound kernels the cleaned seed can be treated with hot 

 water at a temperature of 51° to 52° C. for 10 minutes, a treatment 

 which the writer has found to kill unprotected larvse. According 

 to Humphrey and Potter (17) this treatment is also sufficient for 

 controlling loose smut {Ustilago tritici). If the hot-water bath is 

 to be given, it should be applied directly after the wheat has been 

 separated from the galls. 



Although the methods just described would seem to obviate the 

 necessity of any other means of disinfecting the grain, another 

 means of accomplishing equally good results is available. It con- 

 sists of soaking the gall-mixed seed for about an hour in unheated 

 water and immediately immersing it for 20 or more minutes in 

 water held at a temperature of 52° C. Equally effective has been 

 found either an immersion of the soaked seed for 15 minutes in 

 water maintained at 54°, or for 10 minutes at 56° C. The writer 

 has never been able to find living nematodes within galls given any 

 of these treatments, although these observations are apparently at 

 variance with those of Marcinowski (22), and Davaine (11), who 

 report that they were unable to kill the organism by immersing the 

 galls in water at a temperature of 54° to 56° C. for 10 to 12 minutes. 

 Doubtless they did not previously soak the infected seed. This sup- 

 position would account for the. difference in results, as it takes a 

 much longer time to raise the internal temperature of dry galls or 

 seeds than that of those which are wet. 



