INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 495 



Food Plants. — According to Dr. E. A. Bessey, there are four hun- 

 dred and eighty species and subspecies of plants affected by root knot. 

 A large number of the garden plants are therefore attacked, as are 

 many of the field crops and fruit trees. For definite information 

 concerning the host plants the reader is referred to pp. 10-22, Bulletin 

 No. 217, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1911. 



Control. — The control of this pest is extremely difficult and eradi- 

 cation is almost impossible. In greenhouses the soil may be sterilized 

 with steam or formaldehyde (1 part formaldehyde to 100 parts of 

 water). Summer fallow and frequently turning up the soil and 

 allowing it to dry out will help to reduce the numbers. Irrigated 

 districts are more liable to become infested and are very favorable 

 to the spread of root knot, and in such areas it is especially difficult 

 of control. 



