POISONING COTTON-BOLL WEEVILS. 15 



of a single application was as pronounced as is ordinarily secured 

 from about three applications on a small plat, due, of course, to the 

 constant migration of weevils into the small plat 



COST OF TREATMENT. 



The cost of treatment will, of course, vary widely. In the strictly 

 experimental tests conducted so far it has averaged usually about $1 

 an acre for each application. It must be recognized, however, that 

 it will be possible to reduce this considerably when applications are 

 made on a larger scale, and, with improved machinery, a further 

 reduction will result from the lessened poison requirements. In 

 addition, the probability that it will be possible to utilize carriers and 

 thus further reduce the amount of poison required per acre renders the 

 cost subject to a still greater reduction. It should be remembered, 

 also, that very rarely will it be necessary to poison an entire planta- 

 tion to control the weevil infestation. The weevils on emerging in 

 the spring will always concentrate near the hibernation quarters in 

 which they spent the preceding winter. They remain rather closely 

 at these points until they have multiplied sufficiently to threaten a 

 shortage in the local food supply. For this reason a great part of the 

 cotton is not seriously infested with weevils until some time after 

 midseason and often not until well along in August. Of course the 

 control measures adopted must depend on conditions on each plan- 

 tation, but by concentrating on the more heavily infested cuts just 

 before the weevils become sufficiently abundant to start movement 

 to the remainder of the cotton it will be possible not only directly to 

 benefit the cotton treated, but to protect the remainder of the plan- 

 tation by preventing the weevil migration. In this way the cost of 

 the treatment for a comparatively few acres will be borne by the 

 benefit derived by the entire plantation. In this connection it prob- 

 ably will often prove advisable to give several applications to the 

 more heavily infested cuts and perhaps only a single application to 

 the remainder. 



NECESSITY FOR FURTHER EXPERIMENTAL WORK. 



In conclusion it should be emphasized that the present bulletin is 

 merely a " progress report" and the writer does not wish to be con- 

 strued as in any way advising the general use of these poisons for 

 boll-weevil control. There are now too many doubtful points, 

 especially as regards the technique of application; and, as has been 

 shown, the technique of application largely determines the benefits 

 derived. At the present stage of the investigation it is impossible to 

 outline a definite plan of procedure for the poisoning of weevils under 

 all conditions, and much more experimental work will be required 

 before such a plan can be proposed. With the present lack of infor- 

 mation on so many important points, any attempt to poison the 

 weevil by the inexperienced may very easily result in actual loss. 



