NEMATODE GALLWORM ON POTATOES, ETC., IN NEVADA. 11 
of sugar cane. Many plants of the grass family are practically im- 
mune to this parasite, as has already been indicated. Figure 15 
shows the distortion and enlargement 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. Figure 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 
6 Fic. 13.—Z. Longitudinal section of root tip of 
red-clover plant, showing a young gallworm 
(Heterodera radicicola) embedded in the tissues. 
Fic. 12.—Root system ot a young red- (After B. Frank.) JJ. Longitudinal section of 
clover plant, with swellings caused root tip of red-clover plant, showing four young 
by the gallworm. These enlarge- gallworms (Heterodera radicicola) in the tissues. 
ments should not be confused with (After B. Frank.) JIJ. Longitudinal section of 
the beneficial root nodules caused by root of red-clover plant, near the tip, showing 
nitrogen bacteria nor with the dis- enlargement caused by the gallworm ( Heterodera 
ease known as crown-gall. (After radicicola) and a portion of the young worm. 
B. Frank.) (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 shows a 
distortion of the parsnip caused by the gallworm, while 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 found practi- 
cable to eradicate it from the soil of greenhouses, hotbeds, and cold 
[Cir. 91] 
