16 BULLETIN 1332, IT. S. DEPARTMENT OF AGRICULTURE 
Perennial plilox. — Same dosage as for iris. Keep in the dip for 
from 9 to 18 hours, depending on the amount of soil present on the 
plants. 
Sedum. — Same dosage as for iris. Dip for a period of from 15 to 
18 hours. 
Peony. — Dosage, 0.5 cubic centimeter carbon disulfide per liter 
of water. Dip for a period of 15 hours. 
Care should be taken that the temperature of the dip does not fall 
below 65° F. at any time during the treatment. At the end of the 
period of submergence the plants should be removed from the dip, 
the latter discarded, and the plants, after draining, kept for 48 hours 
in a room at 70° F. Care must be taken that the plants do not dry- 
out before or after the dipping. Plants so treated are then ready 
for shipment outside the quarantined area 10 and not before. Any 
chilling subsequent to the treatment should be carefully avoided, as 
it may lengthen the time required to kill all the larvae. 
COMMERCIAL EXPERIENCE WITH THE METHODS 
During 1922 and 1923 the writers treated by the above methods 
approximately 10,000 Japanese iris, 10,000 perennial phlox, 1,000 
sedum, and 15,000 peony, valued in all at $10,000. There have 
been to date no complaints from the quarantine officials or con- 
signees. 
SUMMARY AND CONCLUSIONS 
Plants of the nature of Japanese iris, phlox, sedum, etc., have 
a matted root system, while peonies are hollow-rooted. It is impos- 
sible to eliminate larvae of the Japanese beetle which may be present 
in these roots by such means as removal of the dirt, by washing or 
by other ordinary methods. The experimental work here outlined 
was therefore conducted for the purpose of evolving a chemical dip 
in which such plants could be immersed for definite periods of time, 
to make sure oi killing any larvae present, and with no resulting injury 
to the plant. 
The results of the work indicate that oil of wormseed (American) 
and carbon disulfide are the best materials to use for this purpose. 
These substances, when added to a hydrophile colloid and water, 
are both capable of forming stable emulsions the toxic principle of 
which is retained indefinitely. 
Oil of wormseed {American). — The primarily active ingredient of 
oil of wormseed is ascaridole, (C 10 H 16 O 2 ). Other ingredients of the 
oil are also toxic in varying degrees. For greater certainty the con- 
centration of the dip is figured in terms of ascaridole rather than in 
terms of wormseed oil. 
When Japanese beetle larvae, with no soil present, are immersed 
for six hours in a wormseed-oil dip the concentration of which is 
equal to 0.5 cubic centimeter of ascaridole to 3 liters of water, the 
larva 1 are killed, provided the temperature of the dip is maintained 
between 05° and 70° F. The experimental residts clearly indicate 
(hat the temperature of the dip is the limiting factor in the success 
of (his method, and under no circumstances must it be allowed to 
fall below 65° F. during the course of the treatment. It is advisable 
lo maintain it at 70° F. f 
'" No rnjurj bai occurred as a result of the wettings received by the plants, In two series of experiments, 
plants were taken out of tin- (lip and Immediately packed in damp moss. Qne lot was placed ineoldstornpe, 
'or two months ihd the Othi r oexl to a hot ^to\e tor several weeks. The first lot was normal when removed, 
from Btorage, whereas the Becond lot made i; inches growth in the moss. 
