NAPHTHALENE AS A GREENHOUSE FUMIGANT 5 



Inc., manufactured a two-wick oil stove with a sheet iron chimney and pan 

 support. Some growers used Union oil stoves with satisfactory results. The 

 rapidity of vaporization in these stoves is controlled by adjusting the height 

 of the flame. 



Hartzell (7) used a three-heat electric hot plate on which was placed a 

 porcelain or sheet iron dish to hold the material, and the writer varied this 

 by constructing a frame over the hot plate which would hold the dish at 

 various heights above the heating unit in order to regulate the amount of 

 naphthalene volatilized in a given time. Hartzell and Wilcoxon (8) developed 

 a naphthalene saturator in which the greenhouse air was blown over large 

 quantities of naphthalene balls for 8 to 15 hours, the concentration of the 

 fumes being governed by the length of time the saturator was in operation. 

 The writer has extended this idea by devising an electric naphthalene fumigator 

 in which the air is heated to about 165° F. (just below the melting point of 

 naphthalene) by passing it through a slowly revolving fan in front of which 

 is placed a series of electrically heated resistance wires. This heated air 

 circulates through a cabinet containing trays permitting exposure to the air 

 of a large part of the crystals in them. The heated air speeds up the volatili- 

 zation of the crystals and the concentration is governed by the amount of 

 crystals in the trays and by the length of time the equipment is operated. 

 As with the Hartzell and Wilcoxon saturator there is no danger of boiling or 

 burning the naphthalene; good circulation of the fumes is provided by the 

 fan, and many of the more susceptible plants which have suffered injury 

 when fumigated by the lamp method have been treated safely with this 

 equipment. 



In 1933, the Hartzell and Wilcoxon saturator (8) was improved to use liquid 

 solutions containing naphthalene. In this apparatus a solution containing a 

 known quantity of naphthalene dissolved in a light motor oil was pumped 

 over a cone in such a way that the air became charged with naphthalene as it 

 was forced through the solution falling from the cone. The amount of naphtha- 

 lene in the solution governed the concentration of the naphthalene vapor in 

 the air. 



In the average greenhouse the most practical equipment appears to be the 

 two-wick oil stove as shown in Plate I. 



Experimental Fumigation Chamber 



The majority of the experiments at the Waltham Field Station were con- 

 ducted in a specially constructed gas-tight chamber containing 1,500 cubic feet, 

 located within a standard greenhouse section. This chamber is about 14 feet 

 long and 10 feet wide with cement floor and side walls 2 feet high on which 

 is constructed a greenhouse frame with 30 x 16 inch glass set in putty. The 

 door and door frame are beveled and closed with a pressure slide latch. Circu- 

 lation is maintained by an electric fan operated at slow speed. The naphthalene 

 was vaporized over an electric hot plate as described above. A constant 

 temperature was maintained by supplying heat from steam pipes, controlled 

 by a thermostat operated by air pressure from an automatic compressor. 

 Constant relative humidity was maintained by the operation of a horse-hair 

 regulator supplied with 30 pounds air pressure controlling a spray of water 

 from a nozzle delivering 8 gallons per hour. An electric fan operating in an 

 exhaust opening with a hinged door enabled the fumes to be evacuated quickly 

 when the fumigation was completed. 



