ARSENICAL COMPOUNDS FOR POISONING THE WORMS. 13? 



will show. In fact, we do not doubt that arsenical poisons will in time 

 be superseded by insecticides that are harmless to man, but as matters 

 stand, the cheapest and most satisfactory remedy has been found in the 

 application of certain arsenical poisons. Another disadvantage of 

 arsenical poisons should be borne in mind, viz., the susceptibility of the 

 cotton plant to their caustic action, the leaves being more or less blis- 

 tered or burnt by an overdose, while leaves, blossoms, squares, and 

 even young bolls may be killed by an excess; so that they are valuable, 

 cceteris paribus^ in j)roportion as they are harmless to the plant. 



We cannot give in simple numbers the minimum quantity of any of 

 these arsenical poisons to be applied with safety to the plant, and at the 

 same time with the desired effect on the worms. This is due to the lack 

 of unity in the application and consequent unequal amounts of poisoned 

 mixtures distributed per acre. If, e. g., by one machine 50 gallons of 

 a given mixture are distributed over one acre, while by another only 

 10 gallons are needed over the same area, it is evident that the minimum 

 quantities of poison required per gallon cannot be the same in both 

 cases. Further, the size of the i)lants, the width of the rows, the state 

 of the weather, the character of the admixtures used, all have an influ- 

 ence in determining the minimum quantity. 



The figures given below must therefore be considered as the average, 

 derived partly from trustworthy experiments which we have made, 

 partly from the rates which are locally adopted and which have i)roved 

 satisfactory by long practice, but which difter widely in different parts 

 of the country. It is to be hoped that with the general adoption of 

 the most improved machines, which distribute the mixtures most eco- 

 nomically, a more uniform rate can be established. 



The question has been raised lately whether a certain amount of 

 scorching by arsenical poisons is really so injurious to the plant as is 

 generally believed, or to put the question in its extreme form, whether 

 a strong overdose of poison does more harm than the worms if they are 

 allowed to have full sway ? If the worms are very numerous they will 

 not only defoliate the plants, but also destroy the blossoms, squares, 

 and bolls, with the exception of the largest of these last. They eat 

 the bark of the more tender twigs, and they very much injure the lint 

 of the open bolls by the excrement and the particles of gnawed leaf 

 which fall thereon, and not only stain it, but depreciate its value, since 

 no ginning can entirely cleanse it. A strong overdose of poison kills 

 the leaves and causes the blossoms and squares to drop, but does not 

 so seriously affect the bolls. Fields stripped by the worms the latter 

 part of August do not fully recover till about two months afterwards, 

 while those which have been seriously injured by poison recover two 

 weeks earlier. It will thus be seen that the injury caused by the worm 

 is of a more serious nature than that caused by arsenical poisons, pro- 

 vided that the worms have been all killed by the poison. A small over- 

 dose of poison blisters or scorches the leaves, or, at worst, kiUs the 



