87 



rainfall. Thirty-three percent of the scales alive at first; 35 per 

 cent, of these dead on the second day, 68 per cent, on the fourth, 84 

 per cent, on the fifth, and 87 per cent, on the twentieth — when the 

 last count was made. 



Tree No. 28. — A fourteen -foot peach-tree, with a five-inch 

 trunk and a ten-foot top; in very poor condition, thoug-h but mod- 

 erately infested with the scale. This tree was reserved as a check 

 upon the experiment, without water treatment of any kind, com- 

 paring- in this respect with No. 20 of Lot 2. Fifty-eig-ht per cent, 

 of the scales were alive on it in the beg-inning-; 76 per cent, of these 

 were dead on the fifth day, and 83 per cent, on the twentieth. May 

 12, the ratio of destruction on this tree was 98.6 per cent. Aug-ust 

 20, three hundred scales were examined; none alive. 



Tree No. jo — A. twelve-foot apple-tree, with an eight-inch 

 trunk and a fourteen-foot top; in g-ood condition, and but moder- 

 ately infested. Treated but once with water, that is with thirty 

 g-allons on the next day after the application of the insecticide. 

 Forty-four per cent, of the scales alive in the beg-inning-; 92 per 

 cent, of these found dead on the sample examined on the fifth day 

 after treatment, and the same ratio on the twentieth day. May 12, 

 the ratio of destruction on this tree was 100 per cent. Aug-ust 20, 

 two hundred scales examined; none alive. 



The Tent Experiment. 



All the preceding- experiments were intended to test the effect 

 of artificial applications of water on the action of the two insecti- 

 cides, these applications being- made in a way to simulate the ef- 

 fects of rainfall. They were interfered with slig-htly by the three 

 periods of lig-ht rain, the effects of which could not be clearly sep- 

 arated from those of the artificial treatment. 



With a view to a test of the effects of rainfall, a small exp»eri- 

 ment was undertaken in which two trees — one treated with the 

 California wash and the other with the Oreg-on wash — were cov- 

 ered with heavy canvas during- the nig-ht and whenever rain threat- 

 ened by day. Two other trees were similarly treated and left at 

 all times exposed, and still two more, selected because of their 

 close correspondence to the experimental trees, were reserved with- 

 out treatment, as checks. This experiment was begun March 20. 

 The trees selected (the only ones remaining- available) were peach- 

 trees on hig-h ground and light soil, heavily infested, and in very 

 poor condition. The drouth of the preceding- season had affected 

 them very seriously, the young- wood being- larg-ely killed, and only 

 29 per cent, of the young- scales on them being- stiil alive. 



