2 BULLETIN 875, U. S. DEPARTMENT OF AGRICULTURE. 
ing advantage of a combination of. factors. In the first place, the 
cotton plant has a peculiar habit of putting on much more fruit than 
it is able to mature. About 60 per cent of the squares which appear 
on the cotton plant fail to reach maturity as bolls, and are shed at 
some time during their development. This does not mean, however, 
that the cotton plant is shedding 60 per cent of its fruit throughout 
the season. This shedding is comparatively slight early in the season 
and increases rapidly as the plants develop until it reaches the point 
where all the new fruit which appears is shed. It has been found 
that up to a certain point the fruit shedding due to boll-weevil at- 
tack merely takes the place of this perfectly normal shedding which 
would be encountered even if the weevils were absent. 
The present system of weevil poisoning is intended merely to keep 
the weevils controlled to such a degree that they will not be able 
to do more than offset the normal shedding of the cotton plants. 
This means, generally speaking, that the weevils are permitted to 
multiply unmolested until they have become sufficiently abundant 
to puncture more forms than would shed normally. Poisoning is 
then started and every effort is directed toward holding the infes- 
tation below this point of danger until the plants have had sufiicient 
time to develop beyond weevil injury as many bolls as they will be 
able to mature. Then poisoning is stopped and the weevils are 
allowed to resume multiplication. Experience has shown that re- 
markably large increases in yield frequently result from a com- 
paratively slight degree of control for a short time during this 
critical period. It has also been very definitely determined, how- 
ever, that this effect is cumulative and can only be secured by start- 
ing the applications at the right time and repeating them at the 
correct time interval. This is the reason the writers urge everyone’ 
contemplating weevil poisoning to decide upon conducting the op- 
eration as thoroughly as recommended or not to attempt it at all. 
Cireular 33 of the Louisiana State Crop Pest Commission, an account of experiments in 
controlling the boll weevil by the application of powdered arsenate of lead which Were 
conducted in Louisiana during 1908 and 1909. 
The studies of the U. ©. Department of Agriculture on the subject of cotton boll weevil 
poisoning were first described in Department Bulletin 731, July, 1918. The present — 
bulletin gives the results of investigations carried on since that time. It is to be followed 
by a detailed bulletin giving descriptions of the various tests and studies which serve as 
a basis for the recommendations made. The latter will also include a discussion of the 
contributions to the subject which have been made by various investigators for many 
years. The work has been conducted under the general direction of Dr. W. D. Hunter. 
The development of dusting machinery has been under the direction of Elmer Johnson, 
of the Bureau of Public Roads. The following have contributed to field and laboratory 
studies: EF. F. Bondy, H. W. Lec, T. F. McGehee, R. W. Moreland, L. Z. Naylor, M. C. 
Rodgers, E. S. Tucker, W. B. Williams, and M. T. Young. The practical field tests 
have been rendercd possible only by the hearty cooperation of the following: Prof. J. W. 
I‘ox, general manager, Delta & Pine Land Co. of Mississippi, Scott, Miss.; Mr. Alex. Y. 
Scott, general manager, Charles. Scott’s Delta Plantations, Rosedale, Miss.; and Mr. 
George S. Yerger, general manager, Maxwell-Yerger Planting Co., Mound, La. 
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