Owing to the influence of meteorological conditions in controlling the weevil, 

 dusting was not advised if the weather continued sufficiently hot and dry for more 

 than a month, especially during the first part of the fruiting season. Dusting was 

 recommended, otherwise, at the usual 4- or 5 -day interval, even in spite of 

 threatening weather. 



Crops dusted with calcium arsenate more than offset the cost of dusting. 

 Estimated cost was $1.18 per acre. Returns were from $18 to $36 per acre. A 

 gas -driven dusting machine was developed. 



1919 - Howard, L. O. Report of the entomologist. U. S. D. A. Bur. Ent. Rpt. 27 p. 



Aug. 14. Wash. 



"The use of powdered lead arsenate or calcium arsenate against the cotton 

 boll weevil . . . which was advocated in last year's report, is being greatly 

 extended with promising results, but care is required in its application, and in- 

 structions are being distributed for this purpose." 



1920 - Anonymous. Service and regulatory announcements. U. S. D. A. Insect and 



Fung. Bd. Announcement 27:609-640. Feb. 20. Wash. 



Includes a notice to manufacturers relative to the labeling of calcium arse- 

 nate for use against cotton boll weevil and notices of judgments given under the 

 Insecticide Act of 1910. 



1920 - Coad, B. R., and T. P. Cassidy. Cotton boll weevil control by the use of poison. 

 U. S. D. A. B. 875, 31 p. July. Wash. 



The system of poisoning described does not aim at the extermination of the 

 boll weevil, but only at a sufficient reduction of infestation to permit the maturing 

 of a full crop of cotton. This depends on the habit of the cotton plant to produce 

 much more fruit than it is able to mature. About 60% of the squares fail to reach 

 maturity as bolls and are shed sometime during development. This shedding is 

 comparatively slight early in the season. It increases rapidly as the plants de- 

 velop, until it reaches the point when all the new fruit that appears is shed. Up 

 to a certain point the fruit shedding due to boll weevil attack merely takes the 

 place of the normal shedding which would occur even if the weevils were absent. 



Generally speaking, weevils were permitted to multiply unmolested until 

 they became sufficiently abundant to puncture more squares than would be shed 

 normally. Poisoning was then started, and every effort was directed toward 

 holding the infestation below this point of danger until the plants had sufficient 

 time to develop, beyond weevil injury, as many bolls as they were able to ma- 

 ture. Remarkably large increases of yield frequently resulted from the compara- 

 tively slight degree of control for a short time during this critical period. A 

 satisfactory effect can be secured only by starting applications at the right time 

 and repeating them at correct intervals. 



The time of starting depends on the percentage of squares in the field that 

 are weevil punctured. As a general rule, operations should start when from 15% 

 to 20% of the squares are punctured, and should be repeated often enough to pre- 

 vent the infestation rising above 25% until the crop is set and the bolls safe from 

 the weevil attack. In certain cases on large plantations it may be possible to 

 confine the weevils to the fields in which they first appear, near their hibernation 

 quarters, as they will not migrate to the adjoining cotton if their numbers are 

 kept down. 



A 4- or 5 -day interval between applications is best. The effect of the poison 

 does not last long, and this interval results in the successful control of the 

 progeny of the first weevil attack if three applications are made under average 

 conditions; more applications are necessary if a longer interval is allowed. If 

 anything happens to interfere with the schedule for a day or so, it can still be 

 continued; whereas if a longer interval were scheduled, all control would be lost. 



The poison is calcium arsenate, used as a dust, with the following specifica- 

 tions: Not less than 40% arsenic pentoxide; not more than 0.75% water-soluble 

 arsenic pentoxide; density not less than 80 nor more than 100 cubic inches per 



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