MEXICAN BEAN BEETLE IN THE SOUTHEAST. A5 
“ZINC ARSENITE. 
The two commercial grades of zinc arsenite experimented with 
the past two seasons are unsafe for use on bean foliage. Zine arsenite 
does not appear to be as injurious to bean foliage as lead arsenate. 
The injury to the bean plant is different from that caused by other 
arsenicals, as burning of the foliage does not always result, but the 
plant is visibly stunted, the color of the foliage turns darker green, 
and the leaves show a tendency to curl. 
Used as a spray at 14 pounds to the acre, reductions in yield below 
those of check plats were obtained. Under conditions of severe 
infestation, excellent insect control is apparently obtained, but 
treated fields do not yield well. On account of the particular type 
of injury to the crop from use of this arsenical, the injury is likely 
to be overlooked and the arsenical rated too high unless accurate 
records of yields are obtained. 
Only one experiment was performed with this material as a dust 
during 1922. Diluted with hydrated lime, plant injury can be 
reduced, but this material is inferior to calcium arsenate and magne- 
sium arsenate on account of toxicity to foliage. It is also physically 
inferior to calcium arsenate for dusting. 
CALCIUM ARSENATE. 
Calcium arsenate or arsenate of lime is extremely toxic to bean 
foliage. Injury to foliage when used as a dust ranged from 60 per 
cent to no injury, depending to a great extent on the degree of 
dilution with hydrated ime. Reductions in yield occurred in much 
the same order. It is certain that calcium arsenate can not be used 
as a dust stronger than 1 to 5 parts of hydrated lime, and that 
appreciable injury may result in some cases with this dilution. 
This insecticide is the most desirable for dusting, from the stand- 
point of physical properties. ; 
Sulphur as a diluent appears to have a slight beneficial effect in 
reducing plant injury, but not enough to make calcium arsenate 
safe at stronger than the 1-1-4 dilution shown in the next paragraph, 
and folage injury occurred in two experiments to the extent of 10 
and 20 per cent, respectively. The beneficial action of sulphur is 
even less noticeable when calcium arsenate is used in greater propor- 
tions. _ 
Excellent results have been obtained with a mixture devised by 
Dr. F. L. Thomas, of the Alabama Agricultural Experiment Station, 
comprising 1 part of calcium arsenate, 1 part of superfine dusting 
sulphur, and 4 parts of hydrated lime. Slight injury, however, has 
occurred under certain conditions with this mixture. Where this 
occurs, it is suggested that the hydrated lime content be increased. 
Diluted with 9 parts of hydrated lime, the high-grade calcium 
arsenate used has ior two seasons been found safe on bean foliage. 
Only one instance of injury to foliage occurred, and that only 10 
per cent. Further comparisons between this cheap mixture of 
materials, available to most growers, and the more expensive sulphur 
mixture are necessary. The slight advantage of this mixture over a 
1 to 9 hydrated lime mixture does not warrant the extra expense, 
_ where growers have to purchase this mixture already prepared, 
since the price is from 2 to 4 times as high per unit of arsenical as 
