ACTION OF LEAD ARSENATE ON FOLIAGE. 33 



which was of a decided enough character to attribute it with cer- 

 tainty to the spraying. Some of the trees which had not been 

 sprayed at all showed a condition which would have been attributed 

 to spraying injury if it had not been known that no insecticide had 

 been applied to them. The most positive results were shown on 

 trees which had received the applications of lead nitrate, but the 

 Jfruit on these trees did not appear to have been injured in the least. 

 By referring to the meteorological report for the period several 

 striking facts will be noticed. March, the month preceding spray- 

 ing, was unusually warm, the mean being 6.6 higher than the 

 average of the month for the preceding thirty-seven years, and also 

 higher than for the month following. This caused the trees to put 

 out their foliage very early. Following this the temperature was 

 below normal for the entire growing season to the following extent: 

 April 4.5, May 4.8, June 7.1, July 1.1, and August 2.6 below 

 the daily average for these months for the preceding thirty-seven 

 years. The rainfall for April, May, and June the months when 

 spraying was actually done was considerably above the average, 

 and the number of clear days for this period was only about one in 

 three. In every case rain fell on the same day or within two days 

 after spraying. These abnormal conditions render the drawing of 

 any satisfactory conclusions from this year's w r ork impossible. The 

 recorded experience of users of Paris green, other arsenicals, and 

 Bordeaux mixture shows that greater injury has occurred following 

 wet weather. This may be true in general, but when spraying is 

 followed soon thereafter by heavy rain the material may be washed 

 off to such an extent that injury would not result from the small 

 amount remaining. Frequent rains which are just sufficient to thor- 

 oughly wet the foliage would naturally produce conditions favorable 

 to the maximum injury. 



EXPERIMENTAL WORK OF 1908. 

 DESCRIPTION OF EXPERIMENTS. 



The results obtained in 1907 indicated that it was not necessary to 

 continue experiments with two applications; therefore in 1908 three 

 applications were made in all except one instance, to which attention 

 is called later. The experiments were conducted on the same apple 

 trees as in the preceding year, but conditions made it necessary to 

 select peach trees in another orchard. These were young vigorous 

 trees and were in their second bearing year. As they were not large, 

 a five-gallon knapsack sprayer outfit was selected for the work as 

 being more convenient. 



