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. It lays its eggs in the standing stem of 



wheat in May or June in the uppermost joint 



available. Several larvae 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 larvae in the field. Infested 



straw not used up by April 1 may be burned, 

 f I j but usually not many adults issue from dry, 



^ ! well-made straw stacks. The best measure is to 



K ■ burn the stubble in the field. Where clover is 



K growing in the stubble, it is possible to choose 



1 a time in winter or spring when the clover 



I has been frozen down, and will not be injured. 



I ;i Rotation should be 



I •^' 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 



larvae will cause less 



loss in yield than in 



backward or weak 



plants. 



Fig. 109. — The 

 Joint-worm. Larva 

 and work. En- 

 larged. Original. 



Fig. 110. — The Joint-worm. 

 Adult. Enlarged and natu- 

 ral size. Original. 



A closely related 

 species, Isosoma hordei Harr., attacks the stems of barley, causing 

 a distortion of the stem at the point of injury, and more or less 

 reduction in yield, as in the case of the species infesting wheat. 

 The recommendations for control are the same. 



