EXPERIMENT STATION BULLETINS. 273 



INSECTICIDES. 



i 



THE ARSENITES — PARIS GREEN AND LONDON PURPLE. 



There is little diflPerence in these two insecticides, the former being arse- 

 nite of copper and the latter arsenite of lime. The London purple is lighter 

 in weight, mixes more readily with water, and is slightly cheaper, but it 

 burns the foliage more readily than Paris green. Each of them contains 

 a small amount of soluble arsenic. 



As a Dust. — The arsenites are often used in the dry form with lime, plas- ' 

 ter, or flour. About the best rule that can be given as to the proportion to 

 use is to combine them so that only a very faint green or purple tint will 

 be seen in the mixture. This will make the poison in the proportion of 

 one part to one hundred or one hundred and fifty. Care should be used to 

 distribute it evenly over the plants and not apply too much. Air-slaked 

 lime seems preferable for the diluent, as it will in a large measure prevent 

 burning of the foliage, should too much of the poison be applied. On low 

 plants this method is quicker and easier in making the application than 

 when applied in the liquid form. 



Mixed with Bran. — Many insects, when hungry, will eat sweetened bran 

 with avidity. Arsenic is mixed in the bran and.dropped in little bunches 

 where wanted. Great numbers of grasshoppers are killed in this way. 

 Success has been reported with climbing cut worms in the same way. Of 

 course one should be careful of stock and chickens at such a time. 



As a Spray. — One pound to 200 gallons of water, or 3 ounces to every 40 

 gallon barrel is not likely to burn the foliage and proves effectual on leaf- 

 eating insects. Occasionally unaccountable injury will occur and it is 

 always safest to use a little milk of lime in the spraying mixture when the 

 Bordeaux mixture (which already has the lime) is not used. A pound or 

 two of the lime, freshly slaked, to each barrel of the mixture is sufficient. 

 It should be considerably diluted and allowed to settle or else strained into 

 the barrel through burlap, or some coarse cloth, before using, or the dirt 

 and impurities will clog the pump and nozzle in spraying. This lime 

 forms a chemical combination with the soluble arsenic and makes it insol- 

 uble. In this condition it kills insects as readily as the soluble arsenic, 

 but does not prove harmful to plant life. Even the tender and susceptible 

 foliage of the peach is not damaged when lime is used. 



As a Paste with Lime. — This is becoming an important preparation as 

 a means of protection against borers, especially the peach tree borer. 

 Make a whitewash paste of the lime and put in enough of the poison to 

 slightly tint the paste. After removing dead, loose bark, whitewash the 

 trunks of the trees the last of May, and at intervals after that, as needed. 

 It kills the young borer in eating through the outer bark, and one should 

 be sure to apply as low on the tiwink as the borers work. 



ARSENATE OF LEAD. 



This is a preparation of arsenic that is comparatively new in insect war- 

 fare. It is a poison like the other preparations of arsenic, though slower 

 in its effect on insects. The important features that commend it are, it is 

 perfectly harmless to the foliage of trees and plants, even when used at the 

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