14 BULLETIN 1313, U. S. DEPARTMENT OF AGRICULTURE 



effect on the eggs. About half a pint per 1,000 cubic feet should be 

 used, and the fumigation should be continued for not less than 18 

 hours. Lloyd states that: 



It has been used for a wide variety of plants, including tomatoes, and no 

 damage has resulted except in one case when the foliage of three young sycamores 

 (Acer pseudo-planatus) * growing in pots turned brown the day after the fumi- 

 gation and was subsequently shed. 



Speyer {23) also found tetrachloroethane effective against adult 

 white flies, but its effect on the red spider was only temporary. 

 The tetrachloroethane, when used at the rate of 10 ounces per 

 1,000 cubic feet, severely injured several varieties of chrysanthemum. 



Richardson and Smith {21) found that 34 and 31 grams per 100 

 cubic centimeters of chloroform and carbon tetrachloride, res- 

 pectively, were necessary to kill aphids, and that the tolerance of 

 the nasturtium plant for these two compounds varied from 5 to 8. 

 Chlorobenzene and commercial trichlorobenzene were less toxic to 

 aphids than carbon disulphide, and their toxic concentrations ex- 

 ceeded the tolerance of the plant. 



Moore {14, 15) used chlorobenzene, p-dichlorobenzene, chloroform, 

 carbon tetrachloride, and chloretone (trichloro tertiary butyl 

 alcohol) in various tests on flies. 



FLUORIDES 



Fluorobenzene at a concentration of 1.9 per cent showed 100 per 

 cent mortality against SitopMlus oryza, but difluorodiphenyl ex- 

 hibited almost no toxicity, owing probably to its slight volatility at 

 the temperature of the test. 



Organic fluorine compounds have not been tested by many investi- 

 gators, probably because they are rare and expensive. 



IODIDES 



The only iodide tested, normal butyl iodide, killed all the weevils 

 at a concentration of 0.8 per cent. 



Moore {14) found iodobenzene to be more toxic to house flies than 

 the corresponding bromine and chlorine compounds. 



Tattersfield and Roberts {24) found iodoform to be nontoxic to 

 wireworms, while iodobenzene was moderately toxic. 



According to Holt {9), cockroaches dusted with iodoform did not 

 succumb until a period of 9 hours had elapsed. 



ALCOHOLS AND PHENOLS 



Methyl alcohol was more toxic than ethyl alcohol, but with this 

 exception the toxicity increased with increasing molecular weight 

 through isoamyl alcohol. Thymol, menthol, and geraniol are so 

 slightly volatile at ordinary temperature as to be practically nontoxic. 



Richardson and Smith {21) found methyl, ethyl, ^-propyl, 

 7i-butyl, capryl, isoamyl, benzyl, and furfuryl alcohols to be ineffective 

 against aphids. Even pure methyl and ethyl alcohols killed less 

 than 95 per cent of the insects. 



Moore {15) found the toxicity of methyl, ethyl, and amyl alcohols, 

 menthol, and thymol on house flies to increase with decreasing 

 volatility. 



Trillat and Legendre {26) showed that methyl, ethyl, propyl, and 

 amyl alcohols had only a feeble toxicity to mosquitoes. 



1 Sycamore maple. 



