130 
PESTS OF GARDEN AND FIELD CROPS 
usually are stunted and give a reduced yield, and the straw tends to 
break down. 
The adult of the grub that does this mischief is a small, black, 
four-winged — fly. 
Fic. 109. — The 
Joint-worm. Larva 
work. En- 
ged. Original. 
species, Isosoma hordei Harr., attacks the 
a distortion of the stem at the point of 
reduction in yield, as in the case of the 
It lays its eggs in the standing stem of 
wheat in May or June in the uppermost joint 
available. Several larva may develop within 
a single stem. The larva remains in the straw 
until the following spring. 
In control cut the straw as low as possible, so 
as not to leave many larve in the field. Infested 
straw not used up by April 1 may be burned, 
but usually not many adults issue from dry, 
well-made straw stacks. The best measure is to 
burn the stubble in the field. Where clover is 
growing in the stubble, it is possible to choose 
a time in winter or spring when the clover 
has been frozen down, and will not be injured. 
Rotation should be 
practiced, and wheat 
kept growing vigor- 
ously so that it may 
be well along by the 
time the adults come 
out to lay their eggs. 
In such plants the 
larv will cause less 
loss in vield than in 
backward or weak Fis. 110.— The Joint-worm. 
=e Adult. Enlarged and natu- 
Pp an tal size. Original. 
A closely related 
stems of barley, causing 
injury, and more or less 
species infesting wheat. 
The recommendations for control are the same. 
