82 



of the first group was 86.5 per cent., making- a difference of S.() per 

 cent., apparently due to the action of water on the insecticide when 

 applied within five days after the orig-inal treatment. In other 

 words and more g^enerally stated, it may be said that in these ex- 

 periments the effect of thoroug-hly watering- the treated tree dur- 

 ing- the first five days after the experiment began, was to dimin- 

 ish, at first, the destructive effect of the insecticide by approxi- 

 mately 5.5 per cent.; but since, as will be presently shown, all 

 differences finally disappeared, the real effect was merely to delay 

 the action of the insecticide in a manner which proved entirely 

 unimportant. 



If we reg-ard as a sing-le group the twenty trees treated with 

 the California wash, we find that 4S per cent, of the 3'oung- 

 scales of the preceding- year were dead when the experiment be- 

 gan; that 43 per cent, of them were killed by the second day after 

 treatment; (>() per cent, by the third; 84 per cent, by the fifth; and 

 approximately 8') per cent, by the twentieth day. The final effect 

 of this wash, as shown by an inspection of eight of these trees on 

 the 12th of May, was the destruction of *)<).2 per cent, of the 

 scales alive at the beginning of the experiment. 



'J liird Lot of Trees.. Oreo on W'as/i. 



This lot of experimental trees corresponds to the first in all 

 particulars except that the Oregon wash of lime, sulphur, and blue 

 vitriol was used as an insecticide instead of the California wash, 

 and that the experiment was made with seven trees instead of nine. 

 The variations in treatment omitted in this lot correspond to those 

 of Nos. 5 and 7 of Lot 1. All were apple-trees, growing in the 

 same orchard as those of the first lot. 



'free Ao. //. — An eighteen-foot tree, with an eight-inch trunk 

 and a twelve-foot spread; in excellent condition, and moderately 

 infested. Sprayed with fifteen gallons of water daily for seven 

 days, beginning March 4, the next day after insecticide treatment. 

 Sixty-seven per cent, of the scales alive at the beginning of the 

 experiment; 85 per cent, of these dead on the third day, *)3 per 

 cent, on the seventh, and 98 per cent, on the twenty-second. By 

 May 12 the percentage killed on this tree was found to be 98.8, 

 and on August 20, out of two thousand scales examined only six 

 were found alive, and these were on branches next an infested 

 hedge. 



'JVee aXo. 12. —A fifteen-foot tree, with an eight-inch trunk 

 and a twelve-foot top; in fair condition, moderately infested with 

 the scale. Sprayed but once, with fifteen gallons of water, on the 



