A NEW PARASITIC NEMA FOUND INFESTING COTTON 
AND POTATOES 
By N. A. Cobb, 
Technologist in Charge , Office of Agricultural Technology , Bureau of Plant Industry , 
United States Department of Agriculture 
INTRODUCTION 
The new species of Tylenchus described below first came to the attention 
of the writer in 1911, when it was found infesting rootstocks of violets 
{Viola spp.) in New York. Practically all the morphological data given 
herein were obtained at that time; later examinations have, for the most 
part, been merely confirmatory. Since its discovery this nema has again 
and again come to notice, first on one plant, then on another, until it is 
now known to infest violets, cotton roots {Gossypium spp.), potatoes (So¬ 
larium tuberosum) , and the roots of camphor (Cinnamomum camphora) 
over an area in the United States extending from Florida to New York 
and as far west as Michigan. 
It injures all the plants upon which it has been found, and, though the 
extent of the possible damage is not yet fully ascertained, it has been 
sufficient to cause growers to make inquiry concerning the origin of the 
injuries they were suffering. The occurrence of this parasite on potatoes 
is of unusual interest, for the reason that any pest found upon potatoes— 
at any rate one whose lesions are similar to those of Tylenchus penetrans — 
is likely to become widely disseminated unless special preventive meas¬ 
ures are adopted. Experience emphasizes the very grave danger of 
spreading serious pests in seed potatoes. If noninfested land be seeded 
with infested potatoes, the result is, in effect, the planting out of the pest 
under conditions very favorable to its increase. 
Unfortunately our knowledge of nemas, especially those attacking the 
roots of plants, is relatively very meager, and in the possession of but few. 
First or last, the existence of root diseases caused by these organisms 
comes to the attention of numerous observers, who, not having the 
necessary literature at their command and not knowing to whom to send 
specimens, often let the matter drop without adequate investigation. 
As it is very desirable to know more about the frequency of this pest, 
its host plants, the extent of the damage done by it, on what plants 
and at what seasons the damage is greatest, and in what kind of soil it 
is most active, this preliminary note aims to enlist the services of such 
observers. 
Journal of Agricultural Research, 
Washington, D. C. 
jy 
(*7) 
Vol. XI, No. I 
Oct. 1, 1917 
Key No. G—121 
