POISONING COTTON-BOLL WEEVILS. 3 



ones. When the cotton was picked from these plats rather surprising 

 results were secured. Every poisoned plat yielded more than the 

 untreated checks, but the most pronounced feature was the much 

 greater increase in yield with the larger number of poisonings. With 

 four applications a gain of about 15 per cent was secured; with five 

 applications this gain was increased to about 35 per cent, while with 

 six applications it was increased about 70 per cent. In other words, 

 a single extra application over four more than doubled the gain, 

 while two extra applications over four increased the gain between 

 four and five fold. As all applications were started at the same time 

 and the extra treatments consisted simply of a continuation that 

 much later in the season, this seemed to point out very significantly 

 the importance of late-season applications. 



POISONING EXPERIMENTS IN 1916. 



The results of these experiments were certainly definite and sig- 

 nificant, but it was considered possible that they might have been 

 due to some peculiar conditions prevailing during that season and that 

 they could not be duplicated during another year. Consequently 

 the experiments during the season of 1916 were planned largely to 

 check the results secured during 1915, with the important change 

 that provision was made for a wider range in the periods of applica- 

 tion. In 1916 the applications in the different experiments extended 

 from the first appearance of the weevils in June until about the 1st 

 of September. On the whole the results in 1916 were just as definite 

 as were those of 1915, and the greater importance of the late-season 

 applications was very plainly demonstrated. In this connection a 

 detailed description of a few of the tests is of interest. 



Probably the most spectacular test of the season and the one 

 which aroused the most interest was conducted in a cut of abandoned 

 cotton. Poor drainage and excessive rains during May and June 

 had prevented cultivation of this cut, and on the 25th of July there 

 were no prospects whatever of a crop. The plants were only about 

 10 inches high and had been so heavily infested by the weevils that 

 there had been no blooms since June. Thus an opportunity was 

 afforded to determine what could be accomplished by poisoning under 

 the most extreme conditions imaginable. An attempt was made to 

 work the cotton out about the 1st of August and a small plat in the 

 center of the cut, only six-tenths of an acre in size, was poisoned. 

 This poisoning was continued during the month of August and 

 surprising results were secured. The weevil infestation decreased 

 rapidly in the poisoned plat and the plants soon started blooming and 

 continued to bloom practically until frost in spite of the fact that all 

 surrounding cotton was very heavily infested with weevils and 

 undoubtedly hundreds, if not thousands, were moving into the 



