STRAWBERRY ROOTWORM ON GREENHOUSE ROSES 29 
serious retardation of the growth. For about six weeks after the 
cut back, during which period no blooms are produced, the plants 
may be sprayed rather than dusted with arsenates to keep the 
foliage protected. When a solution of from 4 to 5 pounds of 
powdered arsenate of lead or calcium arsenate to 50 gallons of 
water, with soap added as a “sticker,” was used to spray the stems 
and swelling buds the same day, so that the beetles found them 
covered with an arsenical, the plants in several infested rose houses 
passed this critical stage with almost no injury. 
For several seasons one florist sprayed his plants with a Bordeaux- 
arsenate of lead mixture which served as a repellent in protecting 
them from the insects’ voracious feeding at the time the plants 
- were making their new growth after being cut back. 
In the earlier experiments at Alexandria, Va., Paris green was 
soon rejected as a spray because no diminution in the numbers of 
adults was noticeable, even though the florist had been using it over 
the entire range of infested houses prior to tests by the Bureau of 
Entomology. No injury to the plants followed its application. But 
in Indiana its use at a greater strength failed to afford any relief from 
the work of the beetles. 
Peterson’s (23, p. 481) ob- 
servations made eight days 
after application indicated 
that Paris green at the 
rate of from 4 to 8 ounces 
to 50 gallons of water did 
not kill the adults in suffi- 
cient numbers to warrant 
its use, and that 8 ounces 
of Paris green to 50 gallons 
of water may burn rose 
. >, 4G, 12.—Fan type of hand duster, useful for ap- 
fohage. Furthermore, it plying insecticidal dusts in greenhouses 
has been noticed during 
the last three seasons that although florists have occasionally felt cer- 
tain that they had succeeded in controlling the strawberry leaf beetle 
by using Paris green, they have found it later continuing its 
ravages. From all this itis apparent that this treatment is ineffective. 
DUSTING WITH ARSENICALS 
The deposit which remains on the leaves of rose plants after 
spraying with arsenicals is objectionable, because it impairs the 
ornamental value of the foliage. Attention was therefore directed 
to other means of application. A dust mixture containing 10 per 
cent, or preferably 15 per cent, of either lead arsenate or calcium 
arsenate and superfine sulphur or other carriers, applied with an 
improved hand duster of the fan (fig. 12) or the bellows (fig. 13) 
type, overcame this difficulty. The following formulas are recom- 
mended and may be purchased or mixed: 
10 per cent formula: Pounds 
Supentinessulphur _ (00 smesh) 228 S28 fis ee Sa a 90 
Lead arsenate or calcium arsenate (powdered) ~-------~- 10 
15 per cent formula: 
Supertiner sulpliurni (200; mesh) =) aS Sees eee ee 85 - 
Lead arsenate or calcium arsenate (powdered) ~-__-____- 15 
