206 THE PLUM CURCIJLIO. 
laboratory by feeding tests with the beetles. (See p. 186.) In each 
case the miik of lime from 2 pounds of stone lime was used to each 
50 gallons of spray. 
Arsenic sulphid (As 2 S 2 ), f pound to 50 gallons of water, was 
applied once April 29. By June 5 the plat treated with the poison 
in rain water showed injury to almost all of the leaves, with con- 
siderable foliage fallen, and this same condition prevailed on the plat 
treated with the poison in well water. On the lime-sulphur plat less 
than one-half as many leaves were injured and very few leaves had 
fallen. 
Arsenic tersulphid (As 2 S 3 ), 6 ounces to 50 gallons of water, applied 
April 13 and 24, showed by May 10 about 75 per cent of defoliation of 
all the trees on the 3 plats. 
Red sulphid of arsenic (As 2 S 2 ), 6 ounces to 50 gallons of water, 
applied April 13 and 29, showed on all plats by June 5 a condition 
similar to the arsenic tersulphid plat, though new foliage was coming 
out. 
Sulpho-arsenate of soda, 6 ounces to 50 gallons of spray, showed 
by June 5 about 60 per cent of the foliage fallen, with those remaining 
badly burned and shot-holed. This condition was true oil the 3 plats 
where the poison was used in well water, rain water, and the self- 
boiled lime-sulphur wash. 
Arsenate of iron in paste form, 2 pounds to 50 galloons of water, 
applied April 29 and June 16, resulted in no foliage and fruit injury 
whatever throughout the season. 
Arsenate of iron in powdered form, 1 pound to 50 gallons of water, 
applied to the trees April 13 and 29 and June 16, also resulted in no 
injury on any of the plats throughout the season. 
Tests of the killing effect of arsenate of iron on the beetles in the 
laboratory indicated, however, that it is a very slow-killing agent; 
but it is probable that the beetles after first eating of the poison are 
rendered incapable of further .important injury. Additional tests 
are planned with this poison on a commercial scale in orchards. 
During 1908 and 1909 feeding tests with beetles and also with 
various caterpillars were made, using various compounds regarded 
as more or less toxic, with a view to their possible substitution for 
arsenicals for use on the peach. Among those tried were the 
f olio wing : 
Black sulphid of antimony (SboS 3 V 
Barium sulphid (BaS). 
Barium carbonate (BaC0 3 ). 
Copper sulpho-cyanid (Cu 4 SCN fl ). 
Carbonate of lead (PbC0 3 ). 
Lead oxid (PbO). 
Zinc oxid (ZnO). 
Zinc cyanid (ZnCN). 
