The Codling-Moth. 137 



understand some of the essential facts in regard to the " whys and 

 wherefores" of the operation which have been brought out at one 

 time and another by the various experimenters during the past ten 

 years. 



What poison to use. — Many comparative experiments have been made 

 with the different arsenical poisons (Paris green, London purple, white 

 arsenic, arseniteof lead, etc.), to determine which is the most effective 

 against the codling-moth. In nearly every case the recorded results 

 show a decided advantage in favor of Paris green over all other poisons. 

 At the present time hundreds of tons of it are used in the United States 

 in combating the codling-moth alone. It is less variable in its com- 

 position than London purple, and the latter is more liable to injure the 

 foliage, but its cheapness and lightness causes many to use it in pref- 

 erence to Paris green.* 



Paris green should be used at the rate of one pound in from 160 to 

 200 gallons of water, or it can be used even a little stronger when mixed 

 with the fungicide, Bordeaux mixture. Careful experiments by Lode- 

 man, Craig and others have demonstrated that the poison is just as 

 effective against the codling-moth when used in combination with 

 the fungicide as when used alone. When used alone there should be 

 added to the Paris green, but more especially to London purple, about 

 twice as much freshly-slaked lime, to prevent any caustic action on the 

 foliage resulting from the presence of soluble arsenic in the poisons; 

 the lime already in the Bordeaux mixture does this. It is, therefore, 

 now a common practice among fruit-growers to use the poison (for the 

 codling-moth) in combination with the Bordeaux mixture (for the apple 

 scab fungus), thus '' killing two birds with one stone." In mixing 

 Paris green or London purple, it is always best to first wet it in a 

 small quantity of water, making a sort of thin paste; if the dry poison 

 is thrown directly into a large quantity of water it cannot be mixed 

 so quickly nor as satisfactorily. 



When to spfay for the codling-moth. — The commonly accepted notion 

 that the eggs of the insect were laid in or on the calyx of the fruit soon 

 after the blossom fell, and the fact that a large percentage of the worms 



* A "Zoektein Poison" was tested by Goff in 1888 and 1889, and " Climax 

 Insect Poison" in Kansas in 1888, but neither these nor other poisons which 

 have been tested have proved eqnal to Paris green in effectiveness. 



