32 BULLETIN 842, U. S. DEPARTMENT OF AGRICULTURE. 



tode galls. As pointed out later, it is possible to free the seed by a 

 simple method, yet it is the part of wisdom to sow clean seed which 

 has been grown in uninfected areas. 



METHODS OF CONTROL. 



Fortunately, the nematode disease appears to lend itself fairly 

 readily to control measures. At least this has been the experience 

 of European agriculturists, and there seems to be no reason why the 

 malady should not respond to proper combative methods in this 

 country. Indeed, the measures employed are so obvious and appar- 

 ently so effective that very little attention has been given to this 

 feature of the disease by research men, no doubt for the reasons 

 given. Successful methods of control are given below, based on the 

 etiology of the disease as presented and on limited field observations 

 by the writer and investigators in England and continental Europe. 



CLEAN SEED. 



To prevent the occurrence of the malady it is absolutely essential 

 that clean wheat unmixed with nematode galls be secured for seed 

 purposes. The disease may be detected most readily at harvest time 

 or after thrashing. If dark, hard galls, containing a white mass of 

 nematodes, are found in the wheat, such grain should not be used 

 for seed unless no other is available. Instead, a supply grown in 

 localities in which the disease does not occur should be obtained. 



However, if clean seed is not obtainable, the nematode galls may 

 be separated from the sound wheat by the so-called salt-brine method, 

 devised by Johnson and Vaughn (18) for removing ergot from rye. 

 Essentially it consists in pouring the infected seed slowly into a 

 water solution containing 20 per cent of common salt (NaCl) and at 

 the same time stirring vigorously. Because of their lower specific 

 gravity, the nematode galls, light kernels, smutted grains, the seeds 

 of some weeds and grasses, and other foreign material will float, 

 while the sound grain will sink. After removing the galls and other 

 floating matter from the surface of the solution, pour off the latter 

 and rinse the grain in water immediately. After being freed from 

 nematode galls the grain should be spread out to dry, after which 

 it is ready for planting. With Dr. A. G. Johnson, the writer has 

 successfully employed this salt-brine method, separating and re- 

 moving every gall from several bushels of wheat which contained 

 more than 50 per cent of the injurious galls. The method is not only 

 entirely effective and inexpensive, but also readily adaptable for 

 operations involving small or large quantities of grain. The germi- 

 nating quality of the grain is not impaired by the treatment. 



