22 
BULLETIN" 571, U. S. DEPARTMENT OF AGRICULTURE. 
Spraying experiments were conducted during the summer of 1915 
for the purpose of determining the effects of various forms of lead 
arsenate on pecan foliage. The pecan trees selected were 12 years 
old and of a good size for their age. The spray material was very 
thoroughly applied by means of a gasoline-power outfit, using a pres- 
sure of about 200 pounds. Table XIX shows the results of this 
work. 
Table XIX. — Spraying experiments against the larvae of the pecan leaf case-bearer at 
Monticello, Fla., in 1915. 
Plat 
No. 
Num- 
ber 
trees. 
Treatment. 
Date of 
applica- 
tion. 
Results. 
Degree of infes- 
tation. 
Extent of arsenical injury 
to foliage. 
I 
II 
18 
18 
12 
12 
5 
Powdered lead arsenate 1| 
pounds, plus 3 pounds of 
lime to 50 gallons of water. 
Powdered lead arsenate 1 
pound, plus 3 pounds of 
lime to 50 gallons of water. 
Paste lead arsenate 3 pounds, 
plus 3 pounds of lime to 50 
gallons of water. 
Paste lead arsenate 2 pounds, 
plus 3 pounds of lime to 50 
gallons of water. 
Paste triplumbic lead arsenate 
2 pounds, to 50 gallons of 
water. 
Paste triplumbic lead arsenate 
2 pounds, plus 3 pounds of 
lime to 50 gallons of water. 
1915. 
Aug. 24 
...do 
Aug. 25 
...do 
...do 
...do 
Practically none. 
do 
Foliage in good condition; 
no appreciable burning. 
Do. 
III 
IV 
do 
do 
Burning of foliage was 
rather serious. 
Margin of leaves rather se- 
verely burned; but the 
trees did not shed their 
leaves prematurely. 
Foliage rather seriously 
burned, especially mar- 
gin of leaves. 
Foliage in good condition; 
no appreciable burning. 
V 
VI 
do 
do 
As shown in Table I, the pecan leaf case-bearer was controlled 
satisfactorily on all plats, but only on Plats I, II, and VI was the 
spraying accomplished without appreciable arsenical injury to the 
foliage. Maximum burning of foliage occurred on Plat V, where tri- 
plumbic arsenate of lead paste alone was used; but even in this case 
the injury was not severe enough to cause premature defoliation. 
Plats III and IV, which received 3 pounds and 2 pounds, respectively, 
of paste arsenate of lead plus 3 pounds of lime to each 50 gallons of 
water, showed rather serious arsenical injury to the margins of the 
leaves, while Plats I and II, which received 1J pounds and 1 pound, 
respectively, of the powdered form of arsenate of lead plus 3 pounds 
of lime to 50 gallons of water, showed no appreciable injury to the 
foliage. From these observations the powdered form of lead arsenate 
appears less likely to cause injury to the foliage than does the paste 
form. 
Under no circumstances was it found safe to use effective dosages 
of lead arsenate (triplumbic or diplumbic) in either the paste or 
powdered form on pecan foliage without the addition of 3 or 4 pounds 
of stone lime per 50 gallons of water. The work with arsenicals indi- 
