﻿6 BULLETIX 1137, V. S. DEPARTMENT OF AGRICULTURE. 



or the empty fiaxseeds 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 held 

 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 3'arcls 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, caifsing 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 larva? 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. 



Fielt symptoms. — The thin stand along the old stubble 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 eeneration. 



