18 MASS. EXPERIMENT STATION BULLETIN 326 



the same conditions as those recommended for naphthalene fumigation. Ex- 

 periments indicate that, although the vapor from these fumigants does not 

 recrystallize and become injurious at the lower greenhouse temperatures, 

 comparatively high temperature and humidity are advisable for maximum 

 efficiency. Under favorable conditions they appear to be slightly more effective 

 against red spider than naphthalene and will give satisfactory control of this 

 pest with one or two fumigations. 



Table 11. — Comparative Effectiveness of Fumigation with 



Naphthalene and with Naphthalene-Paradichlorobenzene 



85-15 for Controlling Common Red Spider. 



Temperature 78° — 85° F. Relative Humidity 80-90 percent. 

 Waltham, Massachusetts. March 1930. 



Compatibility of Naphthalene Fumes with Fungicides and Other 



Insecticides 



Like other fumigants, naphthalene fumes, as used in greenhouse fumigation, 

 leave no residue on the plants which might be injurious to plants when followed 

 by applications of fungicides or other insecticides. 



In experimental fumigations by the writer, no injury to carnations resulted 

 when 40 percent free nicotine liquid was combined with naphthalene in the 

 vaporizing pan, and Wilcoxon et al. (21) report safe and effective fumigations 

 with a combination of naphthalene and sulfur. 



Carnations bearing the residue from previous applications of Bordeaux mix- 

 ture have been fumigated with naphthalene regularly in this section without 

 noticeable injury from the treatment. 



CONTROL OF OTHER PESTS 



As previously stated, naphthalene fumigations are especially effective for 

 combating the red spider. Thrips are also quickly and easily killed by this 

 treatment, but heavy infestations of several other greenhouse pests may be 

 only partially controlled or can be more effectively combated by other means. 

 When regular fumigations with naphthalene are made to control the common 

 red spider, however, other greenhouse pests will be held in check and the crop 

 maintained in a general insect-free condition. 



