December, '19] l.\erimer and ford; harmolita migration 425 



wheat fields adjacent to stubble or in volunteer wheat in or near stubble, 

 the source of infestation of these isolated fields must originate from these 

 places. These data prove that the winged second generation are strong 

 flyers and emerge from wheat in or very near standing stubble, scatter 

 themselves broadcast, and infest all wheat fairly uniformly over the whole 

 general neighborhood. 



Because of the general distribution of the second generation it is cer- 

 tainly not practical to attempt to apply control measures here. The 

 point of attack is certainly in the first generation, the infestation of 

 which is always very limited in area. 



It has already been stated that the plowing under of stubble is effective 

 in preventing further infestation from this species. This is one more 

 reason added to the list why wheat stubble should not be left standing 

 after harvest an}^ longer than possible. In some cases, however, farmers 

 find it impossible to plow under the stubble. In this event, wheat should 

 not be sown adjacent to this infested stubble as shown by the facts al- 

 ready set forth. In the data compiled in Table I, it is seen that prac- 

 tically none of the first generation will migrate more than 30 yards to ovi- 

 posit. This is the key to the whole situation. By planting wheat not 

 closer than 30 yards to standing stubble, one is fairly safe from infesta- 

 tion. Where the stubble can be thrown under without plowing up a hay 

 crop, it should be, but where the hay crop is to be left with the stubble, 

 the following year's wheat should not be sown within 30 yards of it. If it 

 should be, it will act merely as a breeding place for the first generation and 

 the resulting winged second generation will then infest the whole field 

 and nearby fields as well, as is clearly shown by the data embodied in 

 this paper. 



It is also essential to keep down all volunteer wheat in or near stubble. 

 This is most apt to spring up around old shock bottoms. This volunteer 

 wheat will act as a breeding place exactly as \\ill wheat sown next to 

 stubble. 



Summary 



In summarizing the data set forth in this paper, the writers wish to 

 emphasize the following points : Should H. (jrandis increase at its present 

 rate, a great deal of damage will result in the wheat growing region of the 

 United States. The pest hibernates in the stubljlc and the wingless first 

 generation will infest adjacent wheat or volunteer wheat in or near 

 standing stubble, as it affords a breeding place whereby the first genera- 

 tion can survive, thus exposing the entire neighborhood to infestation 

 from the strong thing seconil generation. Should the wingless first 

 generation be deprived of its natuial bleeding places, namely the edge 

 of wheat fields adjacent to standing stubble and volunteer wheat in or 

 near stubble, the result will undowblcdiy be a great decrease in the 

 amount of infestation during the succeetling seasons. 



