Root~knot Eelworm. 
239 
and burn them. No doubt the plant is weakened, but at all 
events the grubs so destroyed will not become flies and do 
injury in the future. 
For treatment on the large scale various dressings have 
been tried in order to prevent the fly from laying its eggs. 
The grub within the leaf is unharmed, but further attack may 
be more or less forestalled. Soot is fairly effective, but better 
results have been obtained by a mixture of soot, lime, and 
earth. The plants should be liberally watered in dry weather. 
Root-knot Eelwoem {Heterodera radicicola). 
Complaints were again received of damage done to cucum- 
bers by this troublesome pest, which causes little galls or 
swellings on the roots, giving them an appearance recalling 
the disease known as “ finger and toe.” Tomato plants also 
suffer from the disease. 
Fig. 3. — Development of Heterodera radicicola, after Ritzema Bos. a. Young eelworm, 
or larva. B, The same after having buried itself in the root. c. Developing male. D. 
Adult female. 
This eelworm is essentially a soil pest, that is, it is present 
in large numbers in infested soil, where it can remain alive 
for a long time, ready to penetrate into any tomato or cucum- 
ber root which it finds at hand. It is therefore fortunate that 
cucumbers are generally grown in definitely circumscribed 
areas of soil, for they can be treated much more satisfactorily 
than would be possible with crops grown in the open. If 
cucumbers fail for no apparent reason some of the roots should 
be examineti for this pest, and the swellings, if present, will at 
once he recognised. Badly knotted roots should be removed 
