MEXICAN BEAN BEETLE IN THE SOUTHEAST. rt 
however, was so low that entirely satisfactory results were not 
obtained under conditions of severe infestation. Magnesium arsenate 
was therefore recommended because it was the only arsenical known 
which could be used without dilution and not cause plant injury. 
OTHER INSECTICIDES. 
Experiments were also conducted with materials other than 
arsenicals. Nicotine dusts were thoroughly tried. Various strengths 
of dust were used, ranging from 0.38 per cent nicotine content to 
4 per cent nicotine content. The insecticidal properties of these 
dusts against the Mexican bean beetle were nil. 
A number of experiments were performed with pyrethrum powder, 
used undiluted as a dust and combined with various diluents, such as 
cornstarch and hydrated lime. Decoctions of pyrethrum powder 
were also used. It was found that pyrethrum powder and certain 
decoctions thereof were very toxic to the adult of the Mexican bean 
beetle, less toxic to the larve, and almost ineffective against the eggs 
and pupz. Because of the high cost of the material, however, and 
the frequent applications required, pyrethrum is_ absolutely 
impracticable for field control. 
i number of new compounds were tried in an experimental way 
‘in cooperation with Dr. William Moore and C. M. Smith. While 
some of these materials may be of value, not one of them has as yet 
warranted recommendation over some of the better known available 
arsenicals. | 
INVESTIGATIONS OF 1922. 
The problem presented in the 1922 experiments in artificial control 
was the use of an arsenical which would not be injurious to bean 
foliage and at the same time would be sufficiently toxic to the Mexican 
bean beetle to insure satisfactory control, the former requirements 
being the more limiting. 
Since magnesium arsenate and calcium arsenate with an excess of 
lime were the most promising arsenicals tested in 1921, these, as well 
as basic lead arsenate, were used on a larger scale than others. 
A few experiments were performed with lead arsenate and zinc 
arsenite in order to check the results obtained the previous season. 
A number of other compounds were also the subject of experiment. 
SPRAYING AND DUSTING MACHINERY USED IN EXPERIMENTS. 
The power sprayer (figs. 11, 12) referred to is a 150-gallon capacity, 
triplex-pump, high-pressure potato sprayer, equipped with a mate 
speed 5-horsepower engine, and was used in experiments as a 4-row 
sprayer, 3 nozzles per row, at 250 pounds pressure. 
An arrangement was improvised to permit the driver to raise and 
lower the boom with one foot when turning around or driving over 
uneven places. 
The wheelbarrow sprayer (fig. 13) is a 15-gallon capacity, hand- 
operated outfit, capable of maintaining 150 pounds pressure at two 
nozzles. It was mounted on a narrow slide and pulled by one horse. 
Two men were required—one to pump and one to spray. The 
arrangement of the nozzles on a U-shaped pipe attached to the spray 
rod made it possible to spray a row at the speed the horse walked. 
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