864 EXPERIMENT STATION RECORD. 



ments a ten-acre field was placed at the disposal of the experiment sta- 

 tion. This field was planted with Green Mountain potatoes in April 

 and divided into 14 plats of 16 rows each, with 2 plats of shorter rows 

 at either end. As insecticides Paris green, Boxal, Paragrene, arsenate 

 of lead, and Arsenoids Nos. 2, 3, 4, and 5, were used. The insecti- 

 cides were applied with water, together with a fungicide, either Bor- 

 deaux mixture or other similar materials. One-half the field was 

 spra^'ed Jul}^ 11 and the other half on Juh" 13. The whole field was 

 sprayed July 21 and 27 and one-half on August 10 and the other half 

 on August 11. A Vermorel nozzle was used for the first application 

 over each row and the rows were passed over twice in opposite direc- 

 tions. The other applications were made with a double Vermorel 

 nozzle. 



Three applications of Paris green at the rate of i lb. per acre kept 

 the potato beetles so reduced in numbers that the fourth application 

 on August 10-11 was unnecessary. Applied at the rate of ^ lb. to 2 

 lbs. of lime per acre, Paris green was more effective in killing the 

 bugs than when mixed with Bordeaux mixture, the latter being appar- 

 ently so distasteful to the beetles that the}^ left the thoroughh" spra5'ed 

 leaves, and thus avoided the leaves with the most Paris green. Para- 

 grene was applied 4 times with Bordeaux mixture at the rate of ^ 11). 

 per acre. The Paragrene used in the experiment was coarser than 

 Paris green, and there was some residue which would not go through 

 a fine Vermorel nozzle. The potato beetles were all destroyed, and 

 onh" a slight injury to the foliage was noticed. Field notes made on 

 the experiments with the Arsenoids show that these substances were 

 as efi'ective as Paris green, but less so than arsenate of lead. Thej' 

 contain more free arsenious acid than the best Paris green. Arsenate 

 of lead is the poisonous element in Boxal and Disparene. Rows 97 to 

 112 were treated 4 times with arsenate of lead and Bordeaux mixture 

 at the rate of 1 lb. per acre. On August 14 it was noted that the 

 beetles were all destroyed. Boxal was also applied 4 times at the rate 

 of 5 lbs., and in another plat at the rate of 10 lbs. per acre. The 

 larger application was more efi'ective in destroving the potato beetles. 

 Disparene was applied to a field of 3 or 4 acres with satisfactory 

 results. 



A number of experiments were conducted with Bug Death as an 

 insecticide. It was found that this substance would cost $8 per acre 

 for each application and that 2 applications about a fortnight apart 

 would be necessary to free the potatoes from the beetles. The process 

 of applying this insecticide is slow and laborious. The substance is 

 chiefl}^ zinc oxid and contains no nitrogen and only a trace of phos- 

 phoric acid and potash. It can not therefore be considered a fertilizer. 

 At the rate of 100 lbs. per acre this substance freed potato vines from 

 the beetles. The beetles, however, were not killed but merely driven 



