- lo - 
cube, or cryblitfe arr- effective against Spilachna varivestls on crops 
of lima "beans grown commonlv on poles and from which pickings are made 
throughout a long period. Insecticide applications made to the pole 
"beans on June lU^ July 1^ and July lU were apparentl:-" reflected through- 
out the season in increas-.d yields, s.s compared with comparable untreated 
plots, pronounced incre-ases in yield being noted on the treated plots 
at the end of the seventh picking (about September 30), The effect of the 
ins-ecticide treatments on the first and second pickings of the crop earlie 
in the season were also strikingly apparent, as judged from the yield records 
made at that tine. It appears that sprays or dust mixtures containing derris, 
cube, or cryolite, when applied properly, are effective in controlling the 
Mexican bean beetle on both bush and pole beans. 
Lima bean leaves sprayed with dilute solutions of rotenone were 
unattacked by Mexican bean beetles. — Broakey and Olcott (US) in I938 . 
According to Burkholder and Crosby (60) in 19'^g, the best means of 
controlling the Mexican bean beetle is to dust with a derris powder contain- 
ing 0.75 percent of rotenone. Good results c?n also be obtained by spray- 
ing with 5 poujids of a finely ground rotenone-bearing povrder. (U percent of 
rotenone) in 100 gallons of water. This dust or spray may be used in place 
of an arsenate or cryolite dust or spray before bean pods begin to form. 
Because of the danger of arsenical residues on harvested beans, the rotenone 
dust or spray must bo used vihon the bean pods are present. Arsenical or 
fluorine (cryolite) poisons may be substituted for rotenone only before the 
small bean pods appear. All the insecticides arc more effective when- applied 
to the lower surface of the bean plants where the beetles and their young do 
most of their feeding, than to other parts, of the plants, 
Rotenone dust is especially efficient, — Cory (§1) in 1932* 
Dunlap and Turner (I06) in 193^ recommendi^d rotenone dusts and 
sprays. The dust should contain at least. 0.5 percent of rotenone, and be • 
applied at the rate of 25 pounds per aero; the spray, 3 "oounds of cube 
(U percent of rotenor.e) in 100 gallons of vrater, 
Fulton .and Howard ( 150 ) in 1^38 reported the results of studies 
of derris residues on bean leaves. Experiments conducted at I3 laboratories 
of the Bureau of Entomolog,v and Plant Quarantine from coast to coast indic- 
ate that the most important factor concerned in the decrease of rotenone 
from sprayed bean plants was rainfall, heavy rains causing greater loss, 
as would be expected. The loss in toxicity was comparati'"'ely slight after 
31 days where no rainfall occurred (Tvrin Falls, Idaho), but vrry rapid at 
Columbus, Ohio, vrithin U days, owing to rainfall. Intense sunlight in 
the Southwest and the South did not account for so great a loss in toxic- 
ity as did .rainfall, although it appeared to be a factor.' 
Fulton and Mason ( 152 ) in I937 noted that in certain field tests 
with insecticides for the control of the Mexican bean beetle the growth 
of the bean plants that formed after the application of a suspension of 
derris or cube in water appeared to receive some protection from infestation. 
