OTHER MINERAL SUBSTANCES USED AGAINST THE WORMS. 153 



All that lias been said under the head of Paris green as to the desir- 

 ability of adding a small quantity of flour or other substance to give 

 adhesiveness to the liquid will hold equally true of Loudon purple. 

 This method is very cheap j labor and machine constituting by far the 

 greatest part of the expense, while the cost of the poison per acre does 

 not exceed 3 cents. 



OTHER MINERAL SUBSTANCES. 

 SALT AND SALTPETRE. 



We have heard common salt frequently recommended as a remedy for 

 injurious insects, and it unquestionably possesses insecticide properties, 

 especially when dissolved in water, affecting and killing the insect upon 

 contact. Unfortunately, however, its effects on the plants are much 

 more marked, and we have thus the same obstacles to its application 

 as with kerosene and other oils. Moreover, salt is decidedly inferior to 

 kerosene as an insecticide, but scarcely less injurious to the plant; hence 

 in the case of salt it is much more difficult to And the "right proportion'^ 

 in which it could effectually be applied; in other words, that proportion 

 of salt which is not injurious to tlie plant will be much too weak to seri- 

 ously affect the worms. 



Nevertheless, in view of the constantly recurring recommendations of 

 salt as remedy for the Cotton Worms in ihe papers, we had some ex- 

 periments made in the field hj Prolessor Stelle and Mr. Schwarz. The 

 former giv^es the following report in his diarj^ : 



September 27, 1880. — SprinMed two rows of cotton across a square acre with a solution 

 made of saltpetre in proportion of 1 ounce to the gallon of water ; also two rows with 

 a solution of common salt, 3 ounces to the gallon of water. 



September 28. — Can see an effect favorable on all the rows of cotton sprayed yester- 

 day, though the worms have not entirely disappeared from any. 



September 29. — Looking over my work on Monday, I find considerably less worms on 

 the saltpetre rows than where nothing has been used, and very few indeed where the 

 common salt was applied. The salt has slightly curled some of the leaves. Sprinkled 

 two rows carefully with common salt in proportion of 2 ounces to the gallon of water. 



September 30. — The rows sprinkled wiih salt yesterday have shown no satisfactory 

 result. 



This report would seem to give a satisfactory result as to the applica- 

 tion of salpeter, but no further experiments have been made so far. 



Much less favorable is the following report by Mr. Schwarz on an 

 experiment made with common salt: 



August 26. — I applied common salt in the proportion recommended to me, viz., at the 

 rate of 1 gallon of salt to 40 gallons of water. The salt was thoroughly dissolved in 

 the water and the liquid apj)lied by means of the fountain pump, wetting the leaves 

 on some plants pretty thoroughly. Upim examination, 16 hours afterwards, a small 

 number of dead worms (not 10 per cent, of the whole number), mostly youug ones, were 

 found, the leaves being somewhat shriveled up even where not exposed to the sun ; but 

 wherever the solution was applied thickly the leaves had assumed a peculiar pale 

 green color and were quite stiff". The worms did not feed upon such leaves, which, on 

 the second day, jiroved to be killed. 



August 28. — Applied the solution at the rate of 1 gallon of salt to 80 gallons of water. 

 No effect upon worms observed the next day or afterwards. 



