14 MISC. PUBLICATION 3 5, II. S. DEPT. OF AGEICULTUEE 



The dusting planes must hare special machinery for carrying and 

 releasing the poison dust. too. There is a little door to the compart- 

 ment holding the dust that can be opened when the airplane pilot 

 is ready for dusting work. This opening can be regulated so as to 

 let out just the quantity of calcium arsenate needed and then closed 

 when no more is necessary. When the door is opened a stream of 

 the poison dust falls through and is violently driven backward and 

 downward by the current of air from the airplane propeller. Grad- 

 ually the dust cloud spreads outward to each side of the plane and 

 drifts in very fine particles to all parts of the cotton plants. (Fig. 

 9.) One airplane will dust as much cotton as 50 cart dusters. 



Airplanes for cotton dusting are not owned by individual cotton 

 planters, as is the case with the usual cotton-dusting machinery. 

 They would be far too expensive for most cotton farmers to own. 

 Instead they are owned by commercial companies who do the work 

 for the planter at so much per acre. The charges for airplane dust- 

 ing which the cotton planter has to pay amount to about the same 

 as it would cost him to do his own dusting with horse-drawn ma- 

 chines. 



A FEW RULES TO FOLLGY/ 



There are a few simple rules that you should follow if you decide 

 to use poison for the boll weevil. They are very easy to remember 

 and not at all difficult to follow. You should learn them and follow 

 them carefully if you want to save your cotton. 



First you should get a supply of pure calcium arsenate in dust 

 form and such dusting machinery as you will need. You should do 

 this well in advance of the season when boll weevils are likely to 

 injure the cotton. If you decide upon airplane dusting, you should 

 make arrangements with one of the airplane-dusting companies dur- 

 ing the winter before the dusting is to be done. 



The next important thing to do is to look over your field soon after 

 the plants have started to put on flower buds. After the flower buds 

 or squares have appeared in the field you should examine some of 

 them every day by breaking them open to see if they have weevil 

 grubs (fig. 3. A) inside them. 



If you find a good many infested squares, pick 100 squares and 

 count the number that have grubs in them. If you find 10 or more 

 infested out of the 100 squares, then it is time 'to begin poisoning. 

 Before you start, however, you had better examine carefully all parts 

 of the field, at least the four corners and the middle. Wherever you 

 find 10 or more squares out of 100 infested, it would be well to dust 

 that part of the field. 



Perhaps you are wondering why you should wait until so many 

 squares are infested before beginning to dust. It is because the cotton 

 plant has the habit of putting out more squares than will ever open 

 into blooms. A great many of these squares drop off without being 

 injured at all. So it is easy to see that up to a certain point the 

 squares which fall on account of boll-weevil injury are merely taking 

 the places of the squares which would fall anyway. 



When you decide to start the work of poisoning, remember that the 

 machines should be run only when the air is calm and the cotton 

 plants are moist with dew. With horse-drawn or hand-operated ma- 



