NAPHTHALENE AS A GREENHOUSE FUMIGANT 17 



Table 10. — Effectiveness of Naphthalene Fumigations under 

 Unfavorable Conditions in Commercial Greenhouses. 



Dosage 2 ounces per 1,000 cubic feet. Crop, Carnation. 

 Temperature 75°-90° F. Relative Humidity 60-80 percent. 

 Waltham, Massachusetts. October and November 1931. 



First Series Second Series 



Number of — 



Fumigations Number of Mortality Number of Mortality 



Spiders Percent Spiders Percent 



1 . 



2 . . . 



3 . . . 



4 . . . 

 None (check) 



387 13.69 253 9.09 



253 35.57 525 57.52 



285 65.61 396 59.59 



227 97.78 357 94.30 



632 9.18 172 



COMBINATIONS OF NAPHTHALENE AND OTHER MATERIALS 



Speyer in England (16, 17) experimented with naphthalene combined with 

 other chemicals without securing results which were definitely superior to those 

 obtained from naphthalene alone. 



Naphthalene and Paradichlorobenzene 



Early in the present studies it was apparent that some method for reducing 

 the recrystallizing temperature of the fumes was desirable. Paradichloroben- 

 zene has a lower recrystallizing temperature than naphthalene but is usually 

 injurious to plants in effective doses. A mixture containing 15 percent para- 

 dichlorobenzene was apparently safe and could be used satisfactorily at 68° F. 

 or above, while naphthalene alone should be used only at 72° F. or above. Such 

 a mixture was manufactured commercially and used extensively. Experimental 

 fumigations, however, have failed to show that this mixture is significantly 

 superior to naphthalene alone, especially after the two or three successive fumi- 

 gations which were necessary to secure a reasonable mortality of red spider. 

 Table 11 shows the results of comparative fumigations in adjoining compart- 

 ments of a commercial greenhouse. 



Other Combinations 



In 1933 naphthalene in a solid solution with sulfur was reported by Wilcoxon, 

 Hartzell, and Youden (21) to be very effective in a special naphthalene saturator 

 with less injury to sensitive plants. 



The same investigators used naphthalene dissolved in motor oil very 

 effectively and safely with exposures of 16 hours in apparatus especially de- 

 signed for this purpose, and found that the concentration of naphthalene in the 

 air was governed by the amount of naphthalene dissolved in the oil, thus per- 

 mitting more control over the dosage during fumigation. 



Recently, two commercial fumigants similar to naphthalene have been 

 developed and used in Massachusetts. These fumigants are liquids containing 

 benzene ring chemicals closely related to naphthalene in combination with other 

 materials. They are vaporized over stoves and lamps and, in general, require 



