4 NEMATODE GALLWORM ON POTATOES, ETC., IN NEVADA. 
for the same nematode which has caused the potato disease in Nevada 
is widely distributed throughout the United States and is causing © 
every year much more damage than is generally understood. 
It is the purpose of the present publication to give some information 
concerning the parasite which is the cause of this potato disease, 
briefly describe its life history, indicate some of the sources of infec- 
tion and methods of transferring the parasite from one place to 
another, and suggest remedial measures for combating the disease in 
Nevada. 
It is of the utmost importance to those concerned to act intelli- 
gently in dealing with the present situation in Nevada. The potato 
crop is one of the most profitable crops at present produced on the 
irrigated lands of Nevada. When not injured by the gallworm the 
potatoes are of very high quality and usually command a higher 
price in California markets than potatoes from any other section. 
It is important, therefore, to prevent the further spread of this 
parasite in the potato-growing sections of the State and so ‘to reduce 
its numbers where it now occurs that it will cease to. be a serious 
pest. This can be accomplished through first locating all of the 
infested fields and then devoting these fields to the production of 
crops upon which the nematode can not live. This location of 
infested areas will require very thorough inspection of all the fields 
which have been used for potatoes within recent years. Such an 
inspection to be thorough must be made by examining the roots of 
plants that are susceptible to the attacks of this species of nematode. 
The inspection should go still farther and include a critical examina- 
tion of all fields on which. it is proposed to plant potatoes. The 
nematode gallworm is parasitic on so many plants that it may 
easily live in the soil for many years if plants which it can attack 
are present. 
A critical inspection of the irrigated lands of Nevada will probably 
show that the nematode gallworm occurs only in small and restricted 
areas. If these infested areas are definitely located and precautions 
are taken to avoid carrying the worm to other fields where it does 
not now occur, and if at the same time these infested fields are 
devoted exclusively to crops which can not harbor the parasite, it 
should be possible in a few years to reduce its numbers to a point 
where it will cease to be a factor of importance. 
CAUSES OF THE POTATO DISEASE. 
The so-called eelworm or gallworm disease (also called ‘‘root- 
knot’’) is caused by a minute nematode worm (/Heterodera radicicola 
(Greef.) Miull.). Figures 1 and 2 show the two sexes of this worm 
enlarged to illustrate various features which are so small as to be 
LCir. 91] . 
