﻿SYMPTOMS OF WHEAT ROSKTTE. 



rapidly decays, leaving the flaxseeds more or. less free, in or on 

 the surface of the soil. This condition persists until llie emergen ■ 

 of the principal spring brood of the fly. 



SPRING PERIOD. 



Field symptoms. — In the case of extremely heavy infestation the 

 previous fall, practically all the plants may be killed. Varying de- 

 grees of infestation give the field a more or less ragged, bunchy ap- 

 pearance, and numerous blank spaces or areas may be evident. As 

 the principal spring generation begins to get in its work, the general 

 color of the field becomes a dark green, and growth is retarded in 

 accordance with the severity of the infestation. 



Plant symptoms. — The effect of infestation on small plants in the 

 spring is practically the same as in the fall, and larvae and flaxseeds 

 are located at relatively the same place on the culms. On larger 

 plants the larvae or the flaxseeds may be found higher up on the stem, 

 but they may easily be found by stripping down the leaf sheath. 

 The culm may be killed or not, depending on its size and the number 

 of larvae or flaxseeds present. 



SUMMER PERIOD. 



Field symptoms. — A thin stand with fallen straw, depending on 

 the severity of the infestation, usually marks an infested field in 

 summer. A light infestation may escape notice. 



Plant symptoms. — Culms that have become weakened at the loca- 

 tion of the flaxseeds usually fall over before harvest. Culms that 

 were heavily infested may have been killed or prevented from pro- 

 ducing a head, but in any case the flaxseeds may be found as the cause. 



COMPARISON BETWEEN THE SYMPTOMS OF WHEAT ROSETTE AND 

 THOSE CAUSED BY THE HESSIAN FLY. 



Since rosette is not apparent in the autumn and since it becomes 

 evident in the spring before the emergence of the adult Hessian fly, 

 there is very little chance to confuse the two maladies during these 

 periods. 



In the late spring there is a possibility of confusion, especially if 

 plants affected by rosette show, in addition, the spring infestation 

 of the Hessian fly. 



In the latter part of the spring, fields affected by rosette sometimes 

 show blank areas caused by the diseased plants being washed out of 

 the soil by unusually heavy rains. Such fields are practically indis- 

 tinguishable from those suffering from a severe attack of the fly, 

 when the infestation of either is general over the field. Owing to the 

 fact, however, that spring fly infestation has never been noted to 

 occur in localized areas or spots in the field, as is commonly the case 

 with wheat rosette, such field spotting observed at any time during 

 the growing season practically precludes fly injury as the sole cause, 

 even though all the affected plants may have been washed away. 



In the case of plant symptoms, fly infestation causes a reduction 

 rather than an increased number of tillers, as is the case in plants 

 affected by rosette. While plants affected by the latter malady often 

 show fly infestation, it will usually be found that many near-by plants 

 affected by rosette show no evidence of such infestation. In the case 

 of plants suffering from fly injury, the larva or flaxseed of the insect 



