222 



REPORT UPON COTTON INSECTS. 



The cheapest mode of applying the poisons is undoubtedly in the wet 

 form ; and I find that they adhere as well when suspended in pure water 

 as when paste is used, though this aids in their suspension. Whenever 

 a solid is used in suspension, frequent stirring is needed to keep it evenly 

 distributed through the water. In Boyall's patent the flour is sup- 

 posed to act as a diluent ; the rosin, to melt by the heat of the sun and 

 thus affix the poison to the leaves of the plant ; the dextrine, to melt and 

 gum the poison to the leaves under the action of water, either as dew or 

 rain. My experiments showed me that flour alone adhered nearly as 

 long as this mixture; and even that it might be replaced in part by gyp- 

 sum or land plaster, but that gypsum alone, or replacing all of the flour 

 in Royall's patent, was removed by the first rain as a general thing. 

 The reason for this is that the first dew converts the flour into a paste, 

 which becomes attached to the leaf, and considerable rain is needed to 

 dissolve and remove it. I find that one pound of Paris green, applied 

 in forty gallons of water to an acre of cotton, will kill the worms to a 

 certainty without injuring the cotton to any appreciable extent, pro- 

 vided there is no rain on it for several days ; but the dry poison, using 

 about twice as much Paris green to the acre, is equally certain and sale, 

 and will withstand far more rain, even if merely mixed with flour. Ow- 

 ing to the cost of the flour, however, and the greater cost of applying it, 

 the dry poison is far more expensive than the wet. 



A. WET POISONS. 



August 7, nine barrels of water were applied, going over about three 

 acres to the barrel. The time spent was from 9 a. m. to sunset, and the 

 first rain fell at about nine o'clock the next morning. The substances 

 used, their quantities, and the number of dead worms just before the 

 rain began are shown by the following table : 



I. Wet poisons applied August 7, 1879. 



Rains occurred nearly every day for about a week after this was ap- 

 plied. On the 9th of August I found no dead worms, and examination 

 with a lens showed very little poison on the leaves ; nor was the cotton 

 scorched except in one or two places where the poison was a little thicker 

 than usual ; but vines of the cow-pea growing in the field were considera- 

 bly injured. The caterpillars continuing to eat, we again poisoned this 

 cotton on the llth, 12th, and 13th of August. 



