COTTON IN WEEVIL-CONTROL EXPERIMENTS 31 



of about 6 inches. Guard plats numbered 1 and 10 were thinned to 

 one plant per hill 12 inches apart. 



DAMAGE BY OVERWINTERED WEEVILS 



While cotton had been grown on an adjoining field in 1922, early- 

 destruction of stalks and unfavorable conditions for hibernation 

 in the vicinity of the field undoubtedly afforded some protection to 

 the 1923 planting. Although careful search was made no evidence 

 of weevil infestation was found until June 14, when punctured 

 squares were seen at three places in the field. Records made on 

 June 20 showed that about 1 per cent of the squares had been damaged 

 by weevils. 



STRIPPING OF FLORAL BUDS 



The entire field was stripped of squares and poison applied on 

 June 20. The mode of procedure in the removal of squares was 

 essentially the same as that used at San Antonio, described on pages 

 6 and 7. The laborers were instructed to remove all squares whose 

 bracts were one-half inch or more long, a size that is attained in 

 about 10 days after the young buds are large enough to be distin- 

 guished readily. There were many squares of this size or larger in 

 the April 5 and April 16 plantings, but only a few in the April 25 and 

 May 4 plantings that were large enough to be removed. Counts 

 were made of the total number of squares removed from representa- 

 tive rows of each plat, and the average number of squares removed 

 per plant was found to be as follows: First planting, 4.5; second 3.8; 

 third, 1.6; fourth, 1.1. During the removal of the squares 78 weevils 

 were captured. 



Field observations indicated that reinfestation from later emerging 

 weevils would have occurred if the squares had been removed earlier 

 than June 20 during 1923. The planting made on April 25 was at 

 the proper stage for stripping on June 20. Plantings made after 

 May 1 could normally be poisoned successfully without stripping, 

 as the weevil emergence was practically complete before the squares 

 were large enough to harbor larvse. 



Calcium arsenate in dust form was applied to the plants on June 

 21 with a hand gun. Heavy rains washed the poison from the plants 

 during the afternoon of that day. As poison should remain on the 

 plants a minimum of 48 hours to be effective, a second application 

 was made on June 22, which remained on the plants until June 27. 

 No further measures were taken to control the weevil during the 

 remainder of the season. 



LATE-SEASON WEEVIL DAMAGE 



Examinations were made frequently in this test for indications of 

 weevil infestation following the removal of squares and poisoning. 

 On July 12 two small infested spots were found, but infestation re- 

 mained very slight and on July 27 was only about 3 per cent. There 

 was no appreciable difference in the infestation of the different 

 plantings. Migration of weevils from other fields began early in 

 August, and by August 13 the experimental field was heavily infested. 

 No attempt was made to control migratory weevils, as adverse 

 weather conditions and defoliation of the plants by leafworms pre- 

 vented the .setting of bolls on any of the plantings after July 31. 



