April, '14] 



DEW: ARSENATE OF LEAD 



163 



ticide its value. The most important point to be determined was 

 whether or not the killing power of arsenates of lead varied 

 directly with the percentage of AsoOj. In order to get data oh foliage 

 effect, time of application, etc., at the same time determining the 

 above points, a peach orchard was selected which was known to be 

 infested by the plum curculio {Conotrachelus nenuphar). The trees 

 selected were all of the Mayflower variety, five years old, and stood 

 in a compact block, all the trees being equally distant from wooded 

 areas. The spraying was done by the writer with a barrel pump, 

 mist nozzle and under a pressure of 110 pounds. The first application 

 was made just as the shucks began to shp, followed in thirteen days 

 by the second. Besides the arsenate of lead the second spray contained 

 self-boiled lime-sulfur wash (8-8-50). A period of drouth extended 

 over the entire time covered by the experiment, April 12 — June 1. 

 During April the precipitation was 1.4 inches (1.9 less than normal) 

 and during May was .45 inches (3.4 less than normal). There were 

 no washing rains, the total of 1.8 inches falling in showers on eight 

 different days. The mean temperature during this time was 63!8°F. 

 All the data presented below is taken from daily records made in 

 the orchard which include the record of the daily fall of fruit as well 

 as of those picked and placed on the market June 1. The experiments 

 were divided into two series. The first included those plots sprayed 

 with a specific number of pounds, calculated on a dry basis of the 

 different forms of arsenate of lead, and the second included those 

 sprayed with a specific number of units of AS2O5 derived from these 

 same forms. The plots were made up of from eight to twelve trees 

 and two from each plot were used as count trees. Below is given a 

 table containing * the data obtained from the first series. 



Examination of these results indicates that the killing power of 

 the arsenate of lead varies directly with the percentage of AS2O5 that 

 it contains. 



The second series of the experiments was based upon the application 

 of specific units of AS2O5 derived from different forms of arsenate of 

 lead and the results are as follows: 



