4 MASS. EXPERIMENT STATION BULLETIN 326 



with variable results. Later, flakes were mixed with sulfur and spread on 

 the steam pipes with more satisfactory results. 



In 1924, broadcasting the naphthalene along the walks of the greenhouse 

 (17) became the approved method of application, using from 2 to 12 pounds 

 in each greenhouse 100 feet long. Continued studies showed that exposures 

 of about 72 hours were advisable and that air temperatures above 74° F. with 

 high relative humidities were preferable. In 1925, the normal dosage was 

 placed at 6 pounds in each 100-foot greenhouse, and a standardized grade of 

 naphthalene known as "Grade 16" which would pass through a screen con- 

 taining 16 meshes to the inch was prepared especially for fumigating. Practi- 

 cally all of this work was the result of efforts to find more effective methods 

 for combating the common red spider 1 on greenhouse cucumbers, and ap- 

 parently this treatment became well established in England. 



This special grade was evidently the first form of naphthalene to be prepared 

 commercially strictly for fumigating purposes, being handled by Geo. Munro, 

 Ltd., who supplied many tons to the cucumber growers in the Lea Valley 

 section about 1925. 



About 1926 Hartzell (6) and the author began experimenting with naphtha- 

 lene as a greenhouse fumigant, and the encouraging results of the preliminary 

 work led several florists in the northeastern United States to fumigate with 

 this material on a practical scale. This work also led to the manufacture and 

 distribution in 1928 by the Fuller System, Inc., Woburn, Massachusetts, of 

 the first commercial naphthalene fumigant to be available in this part of the 

 country. In February, 1932, a patent (U. S. 1,845,977) was issued on this 

 material and methods for its use in greenhouses. This patent apparently 

 covers only the manufacture and use of mixtures composed of naphthalene 

 and other coal tar derivatives rather than naphthalene alone, since the appli- 

 cation was not filed until more than four years after the publication of the 

 reports of Speyer (16), Parker (10), and Hartzell (6). 



About 1930, mixtures containing naphthalene and ground tobacco stems 

 were prepared and used extensively for combating soil inhabiting pests in 

 greenhouse beds and benches. These materials when spread on or mixed with 

 the surface soil were quite effective for eliminating earthworms, snails, sow 

 bugs, and similar soil inhabiting animals, but were not entirely satisfactory 

 for combating pests on the aerial parts of plants. 



EQUIPMENT FOR FUMIGATING WITH NAPHTHALENE 



The application of artificial heat in some form to control the rapidity with 

 which naphthalene is vaporized is the common method of using this material 

 for greenhouse fumigation in Massachusetts. Many lamps and stoves have 

 been devised for this purpose. Most of these devices supply sufficient heat to 

 melt the naphthalene and maintain it in a liquid condition without boiling, 

 while others increase and control vaporization by circulating warm air over 

 crystallized naphthalene. 



Parker (10) used a paraffin lamp over which an inverted cone supporting 

 a pan containing the naphthalene was suspended. Hartzell (6) surrounded an 

 ordinary house lamp with a ventilated sheet iron cone to support the pan of 

 naphthalene. Some growers varied this by substituting a sheet iron chimney 

 with a mica door for the glass chimney on a house lamp. The Fuller System, 



iTetranychus telarius L. 



