366 INSECTS AFFECTING VEGETATION 



HOW TO APPLY ARSENICALS. 



There are three principal methods of applying arsenicals. The 

 wet method, which consists in using these poisons in water in the 

 form of spray, is the standard means, secures uniform results at least 

 expense, and is the only practical method of protecting fruit and 

 shade trees. The dry application of these poisons in the form of a 

 powder, which is dusted over plants, is more popular as a means 

 against the cotton worm in the South, where the rapidity of treat- 

 ment possible by this method, and its cheapness, give it a value 

 against this insect, in the practical treatment of which prompt and 

 economical action are the essentials. This method is also feasible for 

 any low-growing crop, such as potatoes, young cabbages, or other 

 plants not to be immediately employed as food. The third method 

 consists in the use of the arsenicals in the form of poisoned baits, and 

 is particularly available for such insects as cutworms, wireworms, 

 and grasshoppers in local invasions. 



The Wet Method. Either Paris green, arsenite of copper, ar- 

 senite of lime, or London purple may be used at the rate of 1 pound 

 of the poison to 100 to 250 gallons of water, or 1 ounce to 6 to 15 

 gallons. The stronger mixtures are for such vigorous foliage as that 

 of the potato, and the greater dilutions for the more tender foliage 

 of the peach or plum. An average of 1 pound to 150 gallons of w r ater 

 is a good strength for general purposes. The poison should first be 

 made into a thin paste in a small quantity of water and quicklime 

 added in amount equal to the poison used, to take up the free ar- 

 senic and remove or lessen the danger of scalding. An excess of lime 

 will do no injury. The poisons thus mixed should be strained into 

 the spray tank or reservoir, care being taken that all the poison is 

 pulverized and washed through the meshes of the strainer. The use 

 of the lime is especially desirable in the case of the peach and plum, 

 the foliage of which, particularly the former, is very tender and 

 easily scalded. To the stronger foliage of the apple and most shade 

 trees paris green may be applied without danger at the strength of 1 

 pound to 150 gallons of water; with London purple it is always better 

 to use the lime. The method of preparation of arsenate of lead has 

 already been indicated. Lime is not needed with this arsenical. 



If it be desirable to apply a fungicide at the same time, as on 

 the apple for the codling moth and the apple scab fungus, the Bor- 

 deaux mixture may be used instead of water, adding the arsenical to 

 it at the same rate per gallon as when water is used. The lime in this 

 fungicide neutralizes any excess of free arsenic and makes it an ex- 

 cellent medium for the arsenical, as it removes liability of scalding 

 the foliage and permits an application of the arsenical, if necessary, 

 eight or ten times as strong as it could be employed with water 

 alone. 



The arsenicals can not be safely used with most other fungi- 

 cides, such as the sulphate of copper, eau celeste, or iron chloride so- 

 lution, the scalding effects of these being greatly intensified in the 

 mixture. 



