PLATE 4 
INFLUENCE OF SOIL TEMPERATURE UPON CLUBROOT OF 
CABBAGE 
Note absence of disease in the three lower (6°, 9°, 12° C.) and the highest 
temperature (35° C.). 
Plants were grown 5 weeks, at the soil temperatures indicated, in a clay loam 
soil (soil A diluted with sand, see text p. 552 and 555) uniformly infested with 
the clubroot organism. The air temperature for all alike was about 20° C. 
This soil was of a nature favorable for the development of clubroot and was kept 
uniformly at a moisture content found favorable for the development of the 
disease, that is 75 per cent of the water-holding capacity. 
The complete absence of clubroot in the three lower temperatures and in the 
highest temperature must therefore be attributed solely to the inhibiting in¬ 
fluence of soil temperature. 
Largest clubroot development at 20° C., with slightly smaller clubs at 25° C. 
96036—241-6 
