NEMATODE GALLWORM ON POTATOES, ETC., IN NEVADA. 



11 



of sugar eano. Many plants of the grass family are practically im- 

 mune to tliis parasite, as has already been indicated. Figure 15 

 shows the distortion and erdargement of the roots of the tomato 

 caused by -the gallworm. One of the dangerous sources of infestation 

 of new land is through the transplanting of tomato plants grown in 

 hotbeds, where conditions favor the development of the gallworm, 

 and a careful inspection should be made of all tomato plants set in 

 uninfested soil. Hgure 16 shows the enlargement of the roots of the 

 radish caused by the gallworm. This quick-growing vegetable may 

 be used to advantage as an indicator to determine whether or not the 



Fig. 12.— Root system ol a young red- 

 clover plant, with swellings caused 

 by the gallworm. These enlarge- 

 ments should not be confused with 

 the beneficial root nodules caused by 

 nitrogen bacteria nor with the dis- 

 ease known as crown-gall. (After 

 B. Frank.) 



Fig. 1-3. — I. Longitudinal section of root tip of 

 red-clover plant, showing a young gallworm 

 (Heferodera radkicola) embedded in the tissues. 

 (After B. Frank.) //. Longitudinal section of 

 root tip of red-clover plant, showing four j'oung 

 gallworms (Heterodera radicicola) in the tissues. 

 (After B. Frank.) III. Longitudinal section of 

 root of red-clover plant, near the tip, showing 

 enlargement caused by the gallworm (Helerodera 

 radicicola) and a portion of the young worm. 

 (After B. Frank.) 



nematode occurs in any particular soil, though it would be unsafe to 

 assume that a soil was free from nematodes if these enlargements 

 were not conspicuous on the roots of the radish. Figure 17 show^s a 

 distortion of the parsnip caused by the gallworm, wdiile figure 18 

 shows the same condition on salsify. Figures 19, 20, and 21 show 

 the effects of the gallworm on the roots of the okra, cucumber, and 

 lettuce. 



POSSIBILITY OF ERADICATION. 



So far as known there are no effective means of completely eradi- 

 cating the gallworm from infested fields. It has been fountl practi- 

 cable to eradicate it from the soil of greenhouses, hotbeds, and cold 



[Cir. 01] 



