I 



the tabu of 

 tobacco men 



Not Present in All Soils 



The term "frenching factor" is a 

 convenient and desirable name for 

 the cause until a correct answer is 

 obtained. Not found in all soils, the 

 presence of the frenching factor can 

 be determined by growing tobacco at 

 a relatively high soil temperature 

 close to 90°F. If frenching is present, 

 the new leaves on the tobacco plant will 

 show a pinhead mottling usually within a 

 fifteen-day or sometimes within a four- 

 day period. Succeeding leaves are less 

 green, and progressively each leaf is nar- 

 rower than the preceding one. 



New Land Not Immune 



If a soil containing the frenching factor 

 is air-dried, steam-sterilized, or treated 

 with a soil fumigant capable of killing 

 weed seeds, the frenching factor is de- 

 stroyed, and the succeeding planting of 

 tobacco will develop normally. Not much 

 is known about the general distribution 

 of the frenching factor except that it 

 can be found in soils that have a tendency 

 to be moist in drought periods. Soils 

 tested from such areas and on which 

 tobacco has never been grown showed the 

 presence of the frenching factor. Thus, 

 breaking in new land for tobacco culture 

 is no protection against frenching. 



Drainage May Help 



The combination of high soil moisture 

 and a relatively high soil temperature is 

 apparently necessary to activate the 

 frenching factor. Liming the soil inten- 

 sifies the symptoms. If adequate drainage 

 is possible, such installations might be of 

 some aid in protecting the tobacco from 

 this particular disease. 



Above: Frenched tobacco plant grown 

 in high soil temperature, 95 °F. 

 Below: Normal plant grown in low 

 soil temperature, 70°F. 



