Oct. i t 1917 
New Parasitic Nema 
29 
APPEARANCES CAUSED BY THE INFESTATION 
I. ON POTATOES 
On potatoes the lesions are as follows: The tuber is spotted here and 
there, or over its whole surface, by pimples—slightly elevated, some¬ 
what conical areas, 2 to 5 mm. across, having a roundish, broadly ellip¬ 
tical or quadrangular contour. Where one or more pimples run together, 
the contour may be considerably elongated. Near the center of each 
diseased area there arises a minute opening through which the young 
nemas escape to found new colonies. After the potatoes have been dug 
and have shrunken somewhat, the diseased areas may become surrounded 
by shallow channels, owing to the collapse of the immediately adjacent 
tissues, and this shrinkage may be sufficient to cause the whole of a 
diseased area to present somewhat the appearance of a depression 
(fig- 2). 
Fig. 2. —Potato pustules caused by the nema Tylenchus penetrans. At the left a 
double-headed pustule. These are from a potato that had been stored, and show 
the peripheral channel mentioned in the text. 
2. ON VIOLETS 
The rootstocks of violets infested with Tylenchus penetrans display 
brownish, somewhat collapsed areas. As in the potato, the tissues of 
these collapsed areas are inhabited by both sexes of the nema, and the 
infestation may be so intense that areas only a few millimeters in length 
harbor scores of specimens. The violets are very seriously injured, and 
as a result of careful examination, it has become quite evident that the 
nemas are the main cause, and in all probability the sole cause, of the 
injury. 
3. ON COTTON ROOTS 
Cotton plants infested by Tylenchus penetrans have been found in 
Georgia and North Carolina, the nemas being discovered in considerable 
numbers in small, diseased, colored areas on the roots. At the time the 
discoveries were made, the plants were not suspected of being infested; 
they were being examined in a general way in an effort to find out some¬ 
thing about the nemas associated with the roots of cotton plants. No 
definite evidence exists that T. penetrans is a serious pest of the cotton 
plant. 
