68 PLANT QUARANTINE AND CONTROL, ADMINISTRATION [April-June, 
B. Treatment with Hot Water. 
Immersion of the roots in hot water is a simple, quick, and effective method 
for destroying infestations in the roots of certain nursery plants. 
Equipment. — It is necessary to have a water tank equipped with a suitable 
heating device, and a system for circulating the water in order to maintain a 
uniform temperature. Equipment for drying certain plants after treatment 
may be required. 
Condition of plants. — Plants are usually most resistant to hot water when 
they are dormant, and most susceptible when they are growing vigorously. It 
is therefore recommended that treatment be applied only when the plants are 
dormant or semidormant. 
Temperature. — The water must be maintained at a temperature of 112° F. 
for the entire period of treatment. If the temperature falls blow 111.5° the 
infestation may not be destroyed ; if it rises above 112.5° the plants may be 
injured. 
Period of treatment. — The treatment must be continued for 70 minutes after 
the root masses are heated throughout to 112° F. 
Preparation for treatment. — A large proportion of the varieties which are 
treated with hot water have roots nearly free from soil. All excess soil must 
be removed, the roots pruned, and large clumps divided as much as possible 
without injuring the plants. Small plants, bulbs, and root stocks may be 
packed loosely in wire baskets or in other containers providing water can cir- 
culate through the masses. Large plants must be placed individually in the 
water. Before the plants are immersed, thermometers must be inserted with 
the mercury bulbs in the centers qf at least three of the largest clumps, baskets, 
or root masses of each variety, and must be left until the end of the 
treatment. 
Application. — The roots must be immersed completely. The temperature of 
the water may drop for a few minutes after the plants are immersed, but it 
should soon come back to the required degree. A record of the temperature of 
the masses of plants and of the water must be made every five minutes as long 
as the plants are in the water. After the masses are heated to 112° F. the 
temperature must be maintained for 70 minutes. 
Care of plants after treatment. — The insecticidal action of hot water is com- 
plete when the plants are removed from the tank. The way plants are 
handled after treatment may seriously affect subsequent growth. Bulbs and 
tubers should be dry when packed for shipment. Plants should be cooled 
slowly to room temperatures. Plants should not be removed from the hot 
water and heeled in cold soil. Pot the plants, or set them in the ground as 
soon as possible after cooling to room temperature. 
C. Carbon-Disulphide-Emulsion Dip 
Material. — Use 35 per cent miscible carbon disulphide. See page 66. Caution. 
Miscible carbon disulphide and carbon disulphide emulsion are inflammable, 
and the same care should be exercised in handling them as in handling carbon 
disulphide. 
Equipment. — Metal or wooden tanks or tubs in which the plants can be 
treated at a temperature of 70° F. should be provided. 
Condition of the plants. — Dilute carbon disulphide emulsion is least injurious 
to roots when they are dormant or semidormant. Treatment should be applied 
during the dormant period of the variety to be disinfected. 
Temperature. — The temperature of the dilute emulsion must be maintained 
at approximately 70° F. If the temperature falls below 65° F. the treatment 
may not be effective ; if it rises above 70° F. the plants may be injured. 
Dosage. — Miscible carbon disulphide must be mixed with water at the rate 
of 65 cubic centimeters to 10 gallons. 
Period of treatment. — The roots must be immersed for 24 hours. 
Preparation of treating bath. — Measure the tank, taking the distance from 
the bottom to the surface of the water as the depth. Determine the capacity 
from Table 2 or 3, and measure out 65 cubic centimeters of miscible carbon 
disulphide for each 10 gallons. Pour this into the tank, and stir until mixed. 
Do not mix with a mechanical agitator or stir too violently, as this causes 
losses of carbon disulphide. Mix just before using, and do not make up less 
than 10 gallons at a time. 
