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. 
