2 BULLETIN 564, U. S. DEPARTMENT OF AGRICULTURE. 



The investigations of 1916 were conducted under seasonal and 

 climatic conditions differing considerably from those of 1915 and 

 were more extensive, so that it seems that the combined results of 

 the two seasons' investigations may be considered as more or less 

 conclusive. The following report presents a rather brief summary 

 of these experiments, together with the conclusions which seem 

 warranted by the observations. 



The various field experiments were conducted by the junior writer 

 and Messrs. W. B. Williams and T. P. Cassidy, under the direction 

 of the senior writer. 



BRIEF REVIEW OF 1915 EXPERIMENTS. 



Before proceeding with a consideration of the investigations of 

 1916 it is probably well to review briefly the results of the 1915 stud- 

 ies, since the program of work for the second year was based upon 

 these results. In 1915, plat tests of the collection of fallen forms in 

 the cotton field gave an increased yield of 23 per cent over the un- 

 treated cotton. Similar tests of weevil collection were started and 

 the study of weevil infestation and other observations made during 

 the season indicated that a similar degree of control was being se- 

 cured. Unfortunately, the weevil-picking test plats of that year 

 were ruined by hail in the latter part of June, so most of the con- 

 clusions on weevil picking were based on observations made prior 

 to the hail storm and upon comparative efficiency studies of the 

 various means of collecting adult weevils made later in the season. 



The seasonal conditions of 1915 in the neighborhood where these 

 experiments were conducted were very peculiar. Owing to the 

 rather severe winter of 1914-15 the emergence from hibernation in 

 the spring of 1915 was very light and late, resulting in only a slight 

 initial infestation. Following this, the exceedingly dry weather of 

 July produced a very high climatic control of the weevil stages in 

 the fallen forms. This naturally resulted in a comparatively light 

 degree of weevil injury regardless of whether or not control meas- 

 ures were practiced. In view of this very unusually light degree of 

 injury it was considered probable that different seasonal conditions 

 would produce different results from these control measures. 



One interesting feature of the investigation of 1915 was the study 

 of different methods of collection of the weevils and infested forms. 

 Consideration of two factors — (1) the labor supply available and (2) 

 the labor required for the hand picking of either the weevils or the 

 infested forms — showed these measures of repression to be imprac- 

 ticable under the average Delta plantation conditions, hence an effort 

 was made to find some way of reducing the labor requirements of the 

 picking operation. The most promising method considered in this 



