The BoUworm or Corn Earworm. w 



therefore, it is necessary for the young larvso to travel a considerable 

 distance before penetrating the fruit. During this rather aimless 

 wandering the insect eats here and there from the surface of the 

 leaves and stalks. During this short period in the existence of the 

 larva it is susceptible to the action of various arsenical poisons. 



The importance is emphasized of getting the poison on the plants 

 when the numerous young larvae of the August generation begin to 

 hatch and not after the larvae have grown to considerable size. In 

 the later stages they are largely protected from the poison by their 

 habit of burrowing into the squares and bolls and not feeding on the 

 surface where the poison is deposited. 



The time for applying the poison to cotton varies slightly from 

 year to year. The first application should be made when the corn 

 ears are becoming hard. The actual date will range from about 

 July 10 to xVugust 20, according to latitude and seasonal conditions. 

 Close examination of the cotton plants at this time will show the 

 earliest hatched boUworms making minute holes into squares. Often 

 their presence may be detected by the delicate webs wdiich the young 

 worms sometimes spin about the squares. 



Calcium arsenate, powdered arsenate of lead, or Paris green may 

 be used for poisoning, but since the department is advocating the 

 use of calcium arsenate against the boll v.^eevil and since that product 

 is being prepared especially by chemical companies for use on cotton 

 it is to be recommended above the others. It has an advantage over 

 Paris green in not burning the cotton plants and in being less dan- 

 gerous to apply. It is more poisonous to insects than arsenate of 

 lead and is much cheaper. 



While it is possible to apply poison to cotton in the form of a spray 

 (Paris green 1 pound, water 50 gallons), this method is usually 

 impractical, and dust applications are advised. If Paris green is 

 used it is best to mix it thoroughly with some carrier such as air- 

 slaked lime at the rate of 1 pound to 3 of the carrier and make appli- 

 cation at the rate of 6 to 9 pounds of the mixture per acre, according 

 to the size of the plants. In using calcium arsenate from 4 to 5 

 pounds without any diluent should be applied per acre. 



As the use of calcium arsenate as an insecticide is comparatively 

 new and as there is some difficulty connected with the making of a 

 satisfactory product it is advised that those ordering this material for 

 use against the bollworm should call for a product having the specifi- 

 cations given by Mr. B. R. Coad, of the Bureau of Entomology, for 

 use against the boll weevil. These are as follows : 



Arsenic pentoxid, not less than 40 per cent. 



Water-soluble arsenic pentoxid, not more than 0.75 per cent. 



Density not less than 80 or more than 100 cubic inches per pound. 



