STRAWBERRY ROOTWORM ON GREENHOUSE ROSES 83 
The powdered sugar was added in the hope that it might prove 
attractive as a bait, and the arsenical content was increased on the 
theory that it would be moré effective than the 10 per cent mixture. 
The dust was applied in accordance with the florists’ program, 1. e., 
after each syringing, or about two or three times weekly, so that from 
midsummer until November about 1,500 pounds of this material were 
used in keeping the foliage covered. During 1922 the insects failed 
to appear in appreciable numbers, and this infestation was found to 
be so very materially diminished that it became practically negligible. 
As a precautionary meas- 
ure, however, a dust coat- 
ing was maintained cn the 
foliage from February 15 
until the plants were cut 
back or torn out in the 
summer. As was the case 
in the first two establish- 
ments, other control meas- 
ures were employed also, 
and reliance was not placed 
on dusting alone in com- 
bating the beetles. 
It was unfortunate that 
the effectiveness of dusts 
alone, uncomplicated by , 
other simultaneous meth- 
ods of control, could not 
have been tested in a com- 
mercial range; but the fact 
that dusting with arsen- 
icals was the principal con- 
trol measure common to 
all three establishments, 
with the possible exception 
of a limited amount of 
hand picking, indicated 
that this treatment was an 
important factor in reduc- 
ing these infestations. The 
florists who used this dust 
Rolmvellisatished with the-= 27> otek wads by plant te tae 
results obtained from an | | 
insecticidal view-point, and because of the fungicidal value of the 
sulphur in the mixture. 2 
FUMIGATION 
The use of one of the standard fumigants, such as hydrocyanic- 
avid gas and volatile nicotine, which are frequently employed in 
greenhouse fumigation (fig. 15), was given consideration early in 
this investigation. According to several florists the use of volatile 
nicotine painted on pipes was entirely ineffective against the beetles 
(25, p. 70), and subsequent experiments verified this conclusion. In 
the case of hydrocyanic-acid gas it was necessary to determine the 
