THE BOLL WEEVIL. — LOFTIN 285 



growth that set a crop of bolls in a shorter period have helped reduce 

 the time that protection is needed. Calcium arsenate does not kill all 

 the weevils on the plants, nor is that necessary ; it only affords sufficient 

 protection to maintain a favorable balance between the production and 

 shedding of squares so that a normal crop can be produced. 



Another method of application of calcium arsenate that has been 

 used in the Southeastern States is to smear the upper leaves of the small 

 plants before squares are formed with a mixture of calcium arsenate, 

 molasses, and water by means of a homemade rag mop, or "mopping" 

 as it is called. The presquare applictions of sweetened poison kill 

 some of the overwintered weevils but the weakness of this method is 

 that a large percentage of the early emerging weevils die naturally 

 before squares are available for food and approximately one-third of 

 the total weevils always emerge from hibernation after squares are 

 large enough for oviposition and the molasses mixture is no longer 

 effective. A large series of experiments at many localities has shown 

 that sufficient weevils emerge late enough to cause serious loss when 

 conditions are favorable for weevil multiplication and that presquare 

 applications alone cannot be depended upon for control. 



Continued search for new insecticides has shown that calcium ar- 

 senate is still the most effective of the hundreds of materials tested 

 against the boll weevil, including the recently discovered and much 

 publicized DDT. It has a number of disadvantages as well as ad- 

 vantages. It is the cheapest of all the arsenical insecticides, has good 

 dusting qualities, and the commercial calcium arsenate now available 

 seldom injures the cotton plants. However, it does cause injury to the 

 germination and growth of some crops, particularly legumes, on cer- 

 tain light, sandy soils of the Southeastern States when used in large 

 dosages or over a period of years for boll-weevil control. It also de- 

 stroys the natural enemies and causes an increase of the cotton aphid 

 following several applications for control of other insects. In some 

 cases the losses caused by the build-up of aphids largely offset the 

 gains from weevil control, though in recent years it has been found 

 practicable to overcome this by adding nicotine or derris to the calcium 

 arsenate dust. The proper use of calcium arsenate for weevil con- 

 trol often means the difference between a profit and a loss in cotton 

 production. Field plots at Tallulah dusted with calcium arsenate for 

 weevil control annually during the past 25 years averaged 300 pounds 

 of seed cotton per acre, or 30 percent increase in yield, and at Florence, 

 S. C, the 12-year average gains have been 283 pounds. Similar results 

 have been obtained at numerous other localities, with gains of from 

 one-half to a bale of cotton per acre not uncommon where heavy weevil 

 infestation occur on cotton growing on productive soil. It is generally 

 not economical to spend from $3 to $5 per acre per season for weevil con- 



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