18 BULLETIN 837, U. S. DEPARTMENT OF AGRICULTURE. 
almost complete for both materials on the Ives and Concord varie- 
ties. On the Catawbas the arsenate of calcium averaged 90 per 
cent control and the arsenate of lead 96 per cent, but the checks 
adjacent to the arsenate of calcium plats were 12 per cent more 
heavily infested than those adjacent to the arsenate of lead plats 
so the comparisons are very close. These results may indicate that 
the arsenate of lead adhered slightly longer in the season than the 
arsenate of calcium. In recording the spray residue on the fruit 
at harvest time, slightly less was found on the arsenate of calcium 
plats than on corresponding arsenate of lead plats. This feature 
is an advantage in grape-berry moth spraying and is discussed 
later. No foliage injury that could be attributed to the arsenical 
occurred on any of the arsenate of calcium plats. 
Grape spraying experiments were continued in 1919 and foliage 
injury occurred on all plats of the Ives variety where commercial 
arsenate of calcium was used at the rate of 1J pounds to 50 gallons 
of water with 3 pounds of freshly burned stone lime slaked and 
added to each 50 gallons of spray solution. This experience indi- 
cates that the use of arsenate of calcium on the Ives variety is unsafe. 
AKSENATE OF CALCIUM, HOME-MADE PASTE. 
Varied success had been reported from the use of home-made 
arsenate of calcium pastes as sprays for fruit trees. To determine 
the efficiency of these home-made materials for use in sprays on 
grapes the following experiments were conducted. Pastes were 
made according to the following formulas and methods and applied 
in spray solutions to grapes: 
(1) Arsenate of soda + stone lime. 
Sodium arsenate, fused (dry powdered) 60 per cent 
As 2 O e ounces— 30 
Stone lime do 18 
Water do 48 
Total do 96 
The sodium arsenate was dissolved in the water and the resultant 
solution used to slake the lime. A smooth paste arsenate of calcium 
of about 18 per cent As 2 5 content resulted. This was decanted 5 
times to remove the sodium hydroxid. The resultant paste was 
used at the rate of 2 J pounds to 50 gallons to be comparable with 
arsenate of lead (commercial powder 30 per cent As 2 5 ), L| pounds 
to 50 gallons. 
(2) Arsenic acid + stone lime. 
Arsenic acid (liquid) 78 per cent As^Ot, ounces— 10 
Stone lime do 8 
Water do 34 
Total do 52 
