NEMATODE DISEASE OF WHEAT. 37 



tions of these chemicals, which in a short time are injurious to seed 

 wheat. 



The nematode appears to be primarily a parasite of wheat. To a 

 less extent it parasitizes rye, oats, spelt, and emmer, and it has been 

 reported on barley. 



The malady is most commonly spread by means of seed wheat 

 containing nematode galls. It may be distributed in various other 

 ways, such as by the feet of men and animals and by agricultural 

 implements to which dirt containing viable larvae may cling. Sur- 

 face water resulting from rains often transports the parasite from 

 an infested to an uninfested field. 



The disease may be controlled by the use of nematode-free seed 

 in combination with the employment of a 2 to 3 year crop rotation 

 and the application of proper sanitary precautions. Uninfected 

 wheat for planting should be secured, if possible, from localities 

 where the disease does not occur. Nematode-free seed, however, may 

 be obtained from diseased grain by floating off the galls in a 20 per 

 cent salt solution and then treating the remaining wheat with water 

 at a temperature of 50° to 52° C. for 10 minutes. Diseased seed can 

 also be freed from nematodes without removing the galls by im- 

 mersing them in water at a temperature of 54° to 56° C. for 10 to 12 

 minutes. By keeping wheat off infested land for two or, better, for 

 three years, all or most of the nematodes will have starved, so that 

 the subsequent wheat crop will not be appreciably damaged. Every 

 precaution should be taken to prevent the reintroduction of nema- 

 todes to land which is being rotated to control the disease. 



