116 VEGETABLE FORCING 
convenient forms for greenhouse sprayers. Hand 
atomizers are very useful for treating small lots of plants. 
An extensive Ohio grower uses a pressure tank mounted 
on a cart. A very long half-inch hose enables him to 
spray the houses with only an occasional moving of the 
cart. The plan is entirely satisfactory. 
Nematodes (Heterodera_ radicicola).—These little 
pests, which are nearly microscopic in size, are variously 
known as gall worms, eelworms and thread worms. The 
trouble which they cause is often referred to as root knot 
and root gall, and sometimes as big root. The last term 
should not be confused with the malady “big root” and 
“club root” of cabbage and other brassica, caused by a 
slime mold. Nematodes are widely distributed through- 
out the temperate and tropical parts of the world. High 
temperatures and long summer seasons are most favor- 
able for their existence, and for these reasons they are 
most troublesome in southern sections. 
Greenhouse conditions are naturally ideal for nema- 
todes. They are es- 
pecially destructive to 
the cucumber and to- 
mato, and they some- 
times infest asparagus, 
muskmelon, pea, bean, 
beet, celery, carrot, 
eggplant, pepper, on- 
ion, spinach and radish. 
More than 500 kinds of 
plants are said to be 
subject to the attack of 
nematodes. Roots with 
soft, tender tissues, 
such as the cucumber, 
Fig. 38.—Roots of tomato plant completely provide favorable con- 
invaded by gall worms, After Geo. Fy Sd si 
Atensond af ee ditions for this enemy. 
