The Spraying of Obohajbds. 281 



made June 22, two weeks after the first. These two treat- 

 ments protected the apples so well that any additional ones would 

 hardly have been profitable. June was comparatively dry (see p. 268), 

 but the rain-fall during July was considerably above the average, so 

 that the poison stood a good chance of being washed from the trees. 

 It would scarcely seem to be advisable to apply Paris green or London 

 purple more than twice in a season for the codlin moth, unless the rain- 

 fall is very heavy or continuous. Late applications protect the fruit 

 from larv« which hatch late in the season, but their numbers are com- 

 paratively few, and the damage done is so insignificant from a financial 

 standpoint that the returns will scarcely warrant the expense. 



On the whole, it appears to be immaterial in which form or combina- 

 tion the arsenites are applied. The table shows that when only one 

 application was made Paris green gave better results when applied 

 alone than when applied in combination with Bordeaux. But when 

 two applications were made this result is reversed. This coincides 

 practically with the results obtained in 1892,* when it was also found 

 that the action of the poison was not materially affected by the 

 presence of the Bordeaux mixture. • 



Paris green and the ammoniac al solution did not give such favorable 

 results, but as the difference is comparatively slight, conclusions 

 adverse to the combination can scarcely be drawn . 



Two applications of London purple made upon the King gave more 

 sound apples than two of Paris green, only three per cent being found, 

 wormy But Paris green equals this in two applications made upon 

 Fall Pippin, and surpasses it by one per cent in the Maiden Blush. 

 Consequently, no preference can be given to either poison as regards 

 its insecticidal value. It is probable that if each contains the same 

 amount of arsenic, the value of the two is the same. In one 

 respect, however, Paris green has been disappointing. It was 

 found last year, and again this summer, that the foliage of 

 apple trees is more or less injured by its use. When many 

 applications are made using one pound of the poison to 256 

 gallons of water, the injuiy may become serious. After 

 the fourth application had been made to the orchard, it was found 

 advisable to use about a quarter of a pound of quick lime, first slaked 

 in water, to every forty gallons of the poison mixture. This apparently 

 stopped the caustic action of the Paris green. Samples of Paris green 

 from several manufacturers are now being analyzed by the Station 



* See Cornell Experiment Station Bulletin No. 48, December, 1892. 



36 



