70 THE GRAPE EOOT-WORM. 



Table XXV and indicate a much greater efficiency from the arsenate 

 of lead application than from the application of arsenite of lime. 



Vineyardists throughout Erie County have practically abandoned 

 the use of arsenite of lime as a poison spray against the grape root- 

 worm beetle, and arsenate of lead is now used almost exclusively. 



RESULTS OF VINEYARD EXPERIMENTS WITH POISON SPRAYS. 



The field experiments of this investigation were carried on during 

 the three consecutive seasons of 1907, 1908, and 1909, and in view 

 of results obtained by spraying by the senior author during his single 

 season of cooperative work with the late Prof. M. Y. Slingerland 

 the remedial measures tried out were almost entirely along the line 

 of spray applications, it being his belief that the most effective results 

 could be obtained by this method of combat. Some of the principal 

 points upon which information was desired were the effect of poison 

 sprays in ridding the vines of the grape root- worm beetles, the effect 

 of this application in preventing egg deposition by beetles, the rela- 

 tive effect of this treatment on vines of different ages and different 

 stages of infestation, the determination of the immediate seasonal 

 benefit to the vines by prevention of egg deposition, and the cumu- 

 lative benefit both in vigor of vines and crop yield obtained by 

 following up a line of treatment for several consecutive seasons. 



A brief survey of vineyard conditions in the townships of North 

 East, Pa., during the late summer of 1906 enabled us to make a 

 selection of vineyard areas in the various stages of infestation and 

 decline best suited to the working out of these problems. A block 

 of vineyard owned by Mr. Roscoe Davidson, of North East, was 

 selected for the experiment to determine the effect of poison appli- 

 cations. The conditions existing in this vineyard were well suited 

 to the plan of experiment. The area was about 12 acres, thus mak- 

 ing it possible to secure results of commercial value. The vineyard 

 (PL VI) is situated on a northern slope and is divided into four 

 blocks or sections. The soil is of a loose gravelly texture. The 

 lower northern section consists of young Concord vines about 7 

 years planted, the two sections immediately above are made up of 

 vines about 20 years planted and are referred to as old Concords, and 

 the south section consists of a block of 7-year-old Niagara vines 

 referred to in these experiments as young Niagaras. At the time 

 the experiment was undertaken the whole block showed a uniformly 

 heavy infestation of larvae on the roots of the vines. With the excep- 

 tion of the section of young Concords, however, the vines had not 

 yet reached the stage of serious decline and were still producing 

 fairly profitable crops. With the young Concords the case was 

 different. Our attention had been called to these vines late in the 

 summer of 1906 at the time when the fruit was commencing to color. 



