NEMATODE GALLWOEM ON POTATOES, ETC., IN NEVADA. 13 



SUMMARY. 



During the seasons of 1910 and 1911 there has been a serious 

 infestation of certain potato fields in Nevada caused by a nematode 

 fralhvorni known as Heterodera radicicola. This has resulted in hin- 

 dering the marketing of Nevada potatoes in California, where the 

 crop has been sold heretofore. 



Fig. 16.— Radish show- 

 ing root Piilarf;('inents 

 caused by the gall- 

 worm. Care sliould 

 be taken not to con- 

 fuse these enlarge- 

 ments with those of 

 clubroot, a disease oc- 

 curring on cabbage, 

 turnips, and related 

 plants. (After J. C. 

 Neal.) 



Fig. 17.— Parsnip at- 

 tacked and deformed 

 by the gallworm. This 

 disease attacks the 

 roots of hundreds of 

 other kinds of plants. 

 If such roots are used 

 for food the refuse 

 should be cooked or 

 destroyed. Such ma- 

 terial can not be intro- 

 duced into New South 

 Wales and other pro- 

 gressive States. (After 

 N.A.Cobb.) 



Fig. 18.— Roots of salsify, 

 showing enlargements 

 caused by the gallworm. A 

 number of foreign countries 

 have legislated against the 

 introduction of plants and 

 farm produce infested with 

 this disease. (After George 

 F. Atkinson.) 



The parasite causing the disease is a very small unsegmented worm 

 wiiich invades the roots of many different plants, causing malforma- 

 tions and often seriously hindering the grow^th of the plants. The 

 nematode multiplies very rapidly under favorable conditions. The life 

 cycle may be completed within a few^ weeks and each female may 

 lay as many as 500 eggs. 



The nematode may be carried from place to place in the roots of 

 Hving j)lants, in potatoes, on soil on the roots of nursery stock, or 

 with potted plants. It may also be carried from one field to another 

 in earth on farm implements or in irrigation water. Manure from 

 yards where diseased roots or tubers have been fed may carry the 



(Clr. 91] 



