14 BULLETIN 731, U. S. DEPARTMENT OF AGRICULTURE. 



TIME OF DAY. 



Another question of importance is the time of day for application. 

 It is, of course, well known that much more effective poisoning with 

 dry dust can be conducted while the dew is on the plant, as the poison 

 not only clings to the plant better but has much less tendency to 

 drift away from the cotton. A number of tests have been conducted 

 in an attempt to secure some information on this score but were so 

 hampered by the light infestation of 1917 that definite conclusions 

 are not warranted. It is evident that more effective poisoning 

 usually can be done from about 4 p. m. until about 9 a. m. than at 

 other times, although fairly successful results have been secured from 

 applications made throughout the day. It will probably be found 

 that it is advisable to poison as much as possible during the evening, 

 night, and early morning, and to plan to poison during the day only 

 in case of emergency. 



MACHINERY FOR APPLYING THE POISON. 



The machinery for the application must, of course, vary according 

 to the requirements of different conditions. A very satisfactory hand 

 gun of the type shown in operation in figure 9 was already on the 

 market and was largely utilized in the experiments described. This 

 gun, however, will cover only about 4 or 5 acres a day, and it was, of 

 course, necessary to develop machinery adapted to larger areas. For 

 this purpose a power machine has been developed somewhat of the 

 type shown in figure 10. These have been increased in efficiency 

 until now nearly 200 acres per day can be covered by a single machine. 

 In addition, efforts are being made to develop an intermediate type 

 of machine which can be sold comparatively cheaply and which will 

 be adapted to the man planting 50 to 100 acres of cotton, and cover 

 20 to 30 acres per day. 



AMOUNT OF POISON PER APPLICATION. 



The amount of poison required per application has depended so far 

 more on the requirements of the machinery utilized than on the 

 amount necessary for thoroughly dusting the cotton. As a general 

 rule experimental applications have averaged about 5 pounds per 

 acre, but it is apparent that this amount is excessive, and with 

 further improvement in the machinery it will be possible to accomplish 

 an effective poisoning with a much smaller amount. 



NUMBER OF APPLICATIONS. 



The number of applications necessary undoubtedly will vary. 

 This must depend entirely on the conditions prevailing within the 

 particular cut under consideration. In most of the experiments 

 conducted so far from three to five applications were made but, as 

 lias been shown, the effectiveness of these was considerably reduced 

 by the fact that they were on such small plats. In the only case in 

 which experiments on a very large scale were conducted, the effect 



