6 BULLETIN 1137, TJ. S. DEPARTMENT OE AGRICULTURE. 
or the empty flaxseeds will be found at the base of the plant, usually 
under the first leaf sheath. 
SYMPTOMS PRODUCED BY THE WHEAT STRAWWORM. 
FALL PERIOD. 
The wheat strawworm passes the fall and winter in the old stubble 
or straw, so of course it has no effect upon the fall growth of winter 
wheat. 
SPRING PERIOD. 
Field symptoms. — Almost invariably the infestation by the wheat 
strawworm occurs in a field bordering on old stubble or in a field 
which the previous year was in wheat the stubble of which was 
poorly plowed. In the first case the stand is thinner and plants 
shorter next to the old stubble field, and this difference gradually 
shades off to normal as the distance from the edge of the field in- 
creases. This is due to the inability of the wingless form of the 
insect to travel far, and for this reason most of the infestation 
occurs within a strip 30 yards wide bordering on the old stubble. 
Plant symptoms. — Plants infested by the strawworm resemble 
those infested by the Hessian fly except that in the former case 
tillering up to this time has been normal. The larvae develop at 
the base of the plant, causing a bulblike swelling to appear at 
that point. The infested culms are always killed, and frequently all 
the culms are infested. The swelling usually serves to identify the 
injury caused by this insect, and of course the larvae or pupae of the 
insect itself (PI. IV, A) are inside the stem, while in the case of 
the Hessian fly the larva or flaxseed is merely under the leaf sheath. 
SUMMER PERIOD. 
Field symptoms. — The thin stand along the old stubbie field is 
all that serves to mark an infested field in summer. The second 
generation of the insect has enabled it to spread throughout the 
whole field. 
Plant symptoms. — The decaying remains of tillers infested earlier 
in the season are about all that marks the plants which have been 
infested. The larval form of the second generation in the straw 
at this time is difficult to locate except by splitting the infested 
straw. 
COMPARISON BETWEEN THE SYMPTOMS OF WHEAT ROSETTE AND 
THOSE CAUSED BY THE WHEAT STRAWWORM. 
Wheat rosette is not confined to the vicinity of old wheat stubble 
fields, as is the case with the strawworm infestation. If the former 
malady occurs near such a stubble field its presence can be dis- 
tinguished by means of the bulblike swelling on plants infested 
with the insect; also the latter plants develop the normal number 
of tillers in contrast with the excessive tillering caused by rosette. 
The dead and decayed culms in late spring or autumn killed by 
the first generation of the strawworm will still be recognizable by 
their bulbous growth containing the refuse left by the larvae of 
this generation. 
