46 BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 
a home-mixed material. Where dusting sulphur is available, it 
is recommended that the grower obtain the ingredients and mix 
them himself. 
Used as a spray, calcium arsenate is unsafe without an excess of 
lime. At the rate of 14 pounds per acre, with 3 pounds of rock 
lime freshly slaked, or hydrated lime, it is comparatively safe. In 
two experiments no plant injury occurred, and excellent control was 
obtained. In experiment 1(a) (Table 11) 30 per cent of foliage 
injury occurred, however, and it should not be used when magnesium 
arsenate is available. In experiment 7 results identical with those 
following the use of zinc arsenite were obtained. 
The calcium arsenate used in all these experiments was of the very 
highest grade. The water-soluble arsenic content of this material 
did not in any case exceed 0.13 per cent, expressed as metallic arsenic. 
Inferior grades of this compound should be very cautiously applied. 
The bean plant is more susceptible to arsenical injury than the 
‘cotton plant, and grades suitable for cotton dusting may not be 
suitable for use on beans. 
LEAD ARSENATE. 
For two seasons lead arsenate proved too injurious to bean foliage 
to warrant its use in the Southeastern States. Under conditions of 
severe infestation, the protection afforded the foliage is sufficient 
to make it appear that good results are obtained, but the arsenical 
injury is serious enough to reduce greatly the normal yield. 
Injury to foliage from lead arsenate used as a dust ranged from 
60 per cent with the material undiluted to 15 per cent when diluted 
with 9 parts of hydrated ime. The reduction in yield ranged from 
59 to 15 per cent below untreated checks which were injured by 
the bean beetle from 25 to 70 per cent. Slght increases in yield 
resulted from treatment under conditions of medium and heavy 
infestation when injury by the bean beetle to untreated checks was 
35 to 70 per cent. ‘The previous season this material was even more 
injurious, and experiments were therefore reduced during the second 
season. 
Injury to foliage from lead arsenate as a spray at 2 pounds per 
acre ranged from 25 to 40 per cent when rain water was used, and 
from 15 to 65 per cent when water from a stream was used. A 
reduction of 31 per cent in yield occurred under conditions of medium 
infestation when the untreated check plat was injured 40 per cent 
by the bean beetle. It is quite possible that lead arsenate can be 
used more successfully in the North when the beetle reaches that 
section, but in the Southeast it is unsafe. Rain water should be 
used in sections where the water contains soluble salts which de- 
compose lead arsenate and cause an increase in soluble arsenic. 
Lead arsenate corrected with zine carbonate, according to sug- 
gestions from Dr. William Moore, may probably be used ‘success- 
fully on beans. Additional work on this point is necessary. 
This arsenical is more repellent to the adult bean beetle than 
magnesium arsenate, zinc arsenite, or calcium arsenate. 
The lead arsenate referred to is a good grade of the commercial 
lead arsenate, or di-lead arsenate, which is termed ‘‘dilead ortho- 
arsenate, PbHAsO ,” by McDonnell and Smith." 
——— — a ee ee 
10 Jour. Amer, Chem. Soc., vol. 38, No. 10, October, 1916, p. 2030, 
FP rei. TRA 
