Control B:3 



Resistance, due to heredity, and its development, by means of selec- 

 tion and liybridization, is the task of the plant breeder; and althoiigh 

 tlid results may be lasting, their attainment is necessarily a slow 

 process, liesistance or tolerance to nematodes due to non-hereditary 

 factors is becoming of interest with the present-day development of so 

 many new chemicals and the extensive screening programs to test for 

 possible applications. Non- hereditary resistance or increased tolerance 

 to plant nematodes, perhaps, could result from nutritional therapy to 

 compensate for the losses due to the activities of these parasites, or 

 from the application of counteractants or inhibitors of the enzymatic 

 secretions, and to the excretory products of the nematodes. Instances 

 of immunity, tolerance, and inhibition of plant nematodes are known in 

 nature; therefore, development of non-hereditary resistance is con- 

 sidered possible. It is already almost axiomatic to recommend providing 

 ample water and nutrients to valuable nematized plants to compensate for 

 root damage sustained. 



The use of resistance as a practical control measure always calls for 

 careful consideration of the nematode situation in which the resistant 

 plants are to be used, because of the diversity of the nematodes and 

 their relatioAships as mentioned above. 



