18 Farmers’ Bulletin 1262. 
the type most suitable for large farms. This machine is now selling 
at from $250 to $400. 
In the early stages of the dusting work an engine power machine 
was tried and a few of these are still in use, but it has been found 
that they are generally too complicated for satisfactory operation 
except by expert labor. Still other types of machines to suit different 
conditions are in the process of development, but the present supply 
will meet almost any condition fairly well. 
The following condensed rules have been prepared for the guid- 
ance of those planning to poison: 
Use only pure calcium arsenate in the form of a dry pow 
Apply this only in the dust form. 
Purchase this to conform to the following specifications: 
Not less than 40 per cent total arsenic pentoxid. 
Not more than 0.75 per cent water-soluble arsenic pentoxid. 
Density not less than 80 or more than 100 cubic inches per pound. 
Have your county agent send a sample of your calcium arsenate to the 
Delta Laboratory, Tallulah, La., for free analysis to make sure that it is 
satisfactory. 
Use only dusting machinery especially constructed for cotton dusting. 
Poison only when the air is calm and the plants are moist. Practically this 
means making only night applications. 
Use about 5 to 7 pounds of calcium arsenate per acre for each application. 
Start poisoning when the weevils have punctured from ro to 15 per cent of 
the squares. 
Keep your cotton thoroughly dusted until the weevils are under control. 
This usualiy means about three applications at the rate of one every four 
days. 
Then stop poisoning until the weevils again become abundant. 
If the weevils become abundant early enough to injure your young bolls, 
make one or twe more applications late in the season. 
If you have a heavy rain within 24 hours after dusting, repeat this applica= 
tion immediately. 
Do not expect to eradicate the weevils. Poisoning merely controls them 
sufficiently to permit a full crop of cotton and you can always find weevils 
in the successfully poisoned field. 
Keep your cotton acreage low and do everything possible to increase your 
yield per acre, as it costs just as much to poison one-quarter bale per acre 
cotton as bale per acre cotton. 
Always leave an occasionai portion of a cut unpoisoned for comparison 
with the adjoining poisoned tract. This will show how much you have in- 
creased your yield by poisoning. 
INDIRECT MEANS OF CONTROL. 
In addition to the use of poison there are numerous other practices 
which tend to reduce the weevil injury, some of which are of 
general value, while others can be used only locally. The following 
pages list‘a few of the more important of these measures. Even 
when poisoning is practiced the most therough attention should be 
