738 



THE MONTHLY BULLETIN. 



southern part of the State seem to show that an eelworm/ a close rela- 

 tive of H. radicicola, is responsible, in part at least, for the iinpro- 

 ductivity and "decadence" of what were at one time first-class orange 

 groves. Mr. E. E. Thomas,- of the University of California, in his 

 preliminary report on the relation of nematodes to mottled leaf of the 

 orange, brings to light many interesting facts which give promise of 

 solving another one of the serious problems of the citrus industry. 



Fig. 390. — Parsnip badly infested by the 

 root-knot nematode, Heterodera radicicola. 

 (Original.) 



Methods of Distribution. 



Until comparatively recently the ordinary nurseryman and florist 

 knew little of the cause of knots and swellings upon the roots of their 

 stock, and during these years of ignorance the worm has been shipped 

 throughout the temperate world. Owing to the widespread distribu- 

 tion of infested nursery and ornamental stock, the worm became 

 universally established before any legislation was made against such 

 shipments. The general wide dissemination of the eelworm being once 

 established there are many channels present through which this nema- 

 tode may infest a community. The eelworm moves freely in the soil 



•Tylenchulus semipenetrans. 



'Circular No. 85, tJniversity of California. 



