3IO 



Journal of A^griculiural Research Voi. xviii, no. e 



in all these plots show conclusively that the disease does not continue to 

 reappear in successive seasons in the same spots. 



To complete the record of these field observations concerning cotton 

 rootrot as it has been observed in these four plots, the percentages of 

 loss for each season are shown in Table I. These percentages were deter- 

 mined at the end of the crop season by counting the total number of 

 living and dead plants and dividing the number of dead plants by the 

 total number of plants. 



Table i. 



-Percentage of cotton plants taken by rootrot in rotation plots at San 

 Antonio, Tex. 



This table shows that there has been a marked increase since 191 2 in 

 the percentage of plants dying from rootrot, yet the disease has not been 

 so severe in the last two seasons as it was in 191 6. There does not ap- 

 pear to be a very direct or significant relation between the climatic con- 

 ditions and the extent of the disease. 



It is not the purpose here to attempt to explain the anomalous dis- 

 tribution of rootrot spots from year to year or to suggest any cultural 

 method for the control of the disease. It is rather to show that even 

 though the disease does usually occur in well-defined spots in one season, 

 it may not recur there the following season but may appear in a new 

 place. 



