BOLL WEEVIL CONTROL BY USE OF POISON. 13 



after a few days a great deal of unpoisoned tissue is present, which 

 thus reduces the chances of poisoning the weevil. 



A four or five day time interval is best. This not only controls the 

 brood of adults which were present when the applications were 

 started, but also controls their progeny. Under average weather 

 conditions the immature stages developing in the cotton forms at the 

 time when an application is made will continue emerging over a 

 period of at least 12 days. In other words, if the cotton can be kept 

 poisoned thoroughly for a period of about 12 days, the weevils and 

 their progeny are thoroughly controlled. Results vary of course 

 with weather conditions but, generally speaking, two applications 

 with a four-day interval have been found as effective as three or 

 four applications with an interval of a week or more. If conditions 

 are anywhere approaching normal about three applications with a 

 four-day interval will usually reduce the weevil infestation to such 

 . an extent that it will be possible to stop poisoning, and in most cases 

 this degree of control has been sufficient to persist during the re- 

 mainder of the season. Another important point in this connection 

 is that where a 7-day or 8-day interval is used and anything happens 

 to interfere with the schedule, as it often will, the interval may be so 

 extended that practically all control will be lost and the operation 

 will become a complete failure; whereas, when the shorter interval 

 is attempted, any mishaps will still leave the applications sufficiently 

 close together to give a fair degree of control and the worst that can 

 be expected is the necessity of making one or two extra applications. 



It should also be taken into consideration that when the short in- 

 terval is used the infestation can be permitted to become decidedly 

 higher than would otherwise be safe. In other words, the control 

 is so positive and the reduction of weevils so great that it is usually 

 safe to permit the weevil practically to reach the point of becoming 

 injurious to the cotton before making any application. 



The machinery requirement must be considered very carefully in 

 connection with the time interval between applications, as the acre- 

 age which can be handled by any particular machine is proportion- 

 ately decreased as the interval is shortened. This of course in- 

 creases the investment in machinery required per acre. But this cost 

 is offset by the decrease in the number of applications necessary and 

 the consequent reduction in cost of poison and labor. It is offset to 

 an even greater extent by the better control secured and the resultant 

 higher yield of cotton. Of course at present the machinery supply 

 is decidedly short and machines are now high in price compared to 

 what they will be in the future when their production is standard- 

 ized, so it is quite a problem to determine just how much the acreage 

 allotment for each machine can be reduced without making the ma- 



