Appendix. 1G9 



showers, the whole of the following day, March 21, to an amount esti- 

 mated b5' Mr. Titus at more than thirty gallons per tree. 



The temperature of the twentieth was thirty-four degrees at seven a. m. 

 and fii'ty-seven degrees at noon; that of the twenty-first was forty-four at 

 seven a. m. and fifty-two at noon, the wind from the southeast both 

 days. Observations on this experiment continued only until the twenty- 

 fifth, but counts of the scales were made daily up to that time — three 

 thousand scales for the four experimental trees, and two thousand and 

 fifty for the two checks. 



In this small experiment no differences of any significance were made 

 out in the action of the insecticides, the total general effect being the 

 destruction of approximately ninety-five per cent of the scales, and varia- 

 tions from this average in the individual trees being too slight to take 

 into account. So far as any conclusion can be drawn from an experiment 

 on so small a scale, we can only infer that a rainfall such as described, oc- 

 curring at the time of the insecticide treatment, would have no appre- 

 ciable effect on the action of either of the washes. The apparent extra- 

 ordinary efficiency of the washes on these trees is plausibly explained by 

 Mr. Titus, as connected with the poor condition of the trees and the 

 probable consequent low vitality of such of the scale insects as remained 

 alive. 



EFFECTS OF EAIK AXD WATER SPRAYS IN WASHING OFF DEAD SCALES. 



Noticing that many scales were loosened and washed away after in- 

 secticide treatment of the trees, Mr. Titus made some careful counts from 

 day to day of selected lots of scales on the experimental trees to de- 

 termine the circumstances and the ratio of their diminution in numbers. 

 Selecting, for example, a definite part of a branch, counting a hundred 

 scales on it when the insecticide was applied and marking the area oc- 

 cupied by them, he counted them each day thereafter for several days 

 and thus arrived at an exact conclusion as to the effect of the fluid appli- 

 cations and the incidental rains. Thus, on No. 1, three hundred scales 

 counted March 3 v/ere reduced to one hundred and eighty-eight by March 

 15 — a loss of thirty-seven per cent. On No. 11, four hundred scales were 

 reduced in the same time to two hundred and twenty-three — a loss of 

 twenty-two per cent. Both these trees, it will be remembered, were 

 sprayed with the insecticide March 3, and daily thereafter for one week 

 with fifteen gallons of water. On No. 3, one hundred scales were reduced 

 in eight days to seventy-two — a loss of twenty-eight per cent, this tree 

 having been three times sprayed, vv'ith fifteen gallons of water each time. 

 On No. 6, sprayed once with thirty gallons, the loss was twenty-five per 

 cent in eight days; and on No. 14, receiving the same treatment except 

 that the insecticide used was the Oregon instead of the California wash, 

 the loss for the same period was eleven per cent. No. 21, sprayed also 

 but once, with fifteen gallons of water, lost twenty per cent of its scales 

 in seven days; No. 42, exposed to rains tor a day and a night, lost in 



