14 ~—s MISC. PUBLICATION 35, U. S. DEPT. OF AGRICULTURE 
The dusting planes must have 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 FOLLOW 
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- 
re 
