30 BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 
ARTIFICIAL CONTROL. 
At the outset the problem of artificial control of the Mexican bean 
beetle appeared to be a matter of the application of the proper 
stomach poison to the bean foliage. Some experience had been 
gained along these lines by State and bureau workers in the West 
and Southwest. The general conclusion from these investigations 
was that lead arsenate and zinc arsenite are the most satisfactory 
arsenicals for the control of the Mexican bean beetle, these being 
recommended as sprays. 
INVESTIGATIONS OF 1921. 
ARSENICALS. 
The work for 1921 was therefore planned with a view to learning 
what results could be obtained in the Southeastern States by these 
sprays. A number of other arsenicals were also tried, chiefly calcium 
arsenate and magnesium arsenate. A large series of experiments 
was conducted with various dilutions of all of these arsenicals, both 
as sprays and as dusts. After completing the first experiments, it 
appeared as though lead arsenate and zinc arsenite were promising 
materials, since check plats were totally destroyed and excellent 
ea was afforded treated plats. Experiments were continued, 
oweyer, and it was soon learned that the plant injury caused by 
these arsenicals makes them hardly worthy of recommendation to 
the grower, on account of reduced yields. 
Different factors were found fo influence this plant imjury. 
Attention was called by Dr. William Moore, formerly of the Bureau 
- of Entomology, and C. M. Smith, Insecticide and Fungicide Lab- 
oratory, Bureau of Chemistry, to the effect on lead arsenate of the 
water available in the Birmingham district. Further experiments 
were performed, and it was learned that lead arsenate is absolutely 
unsafe for application to bean foliage, even with distilled water, or 
diluted with hydrated lime and used as a dust. It was also learned 
that zinc arsenite causes a serious reduction in yield, even though 
the injury to the plant is not as noticeable as injury caused by lead 
arsenate. Experiments proved that calcium arsenate is absolutely 
unsafe for bean foliage without the application of an excess of lime 
along with the material. These results were also obtained when the 
materials were used as dusts. 
Throughout all the experiments magnesium arsenate, a commer- 
cial preparation which has not been generally used on account of the 
injury to foliage of different kinds of fruit trees, was found to be safe 
on bean foliage, even though used with the water of the district, 
which is relatively high in soluble sodium salts. Under conditions 
of severe infestation in 1921 unsatisfactory results were obtained 
with dilutions of those arsenicals which were injurious to foliage in 
the undiluted state. 
Since magnesium arsenate is not generally available to bean 
oTOWwers, and because of the fact that growers in the Southern States 
were more familiar with dusting methods than with spraying methods, 
a tentative recommendation was made that calcium arsenate of a 
high grade be diluted with 9 parts of hydrated lime and be applied 
to the foliage as a dust. The amount of arsenic in this mixture, 
